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FUSING LIDAR AND IFSAR DEMS: A SEVEN-STEP METHODOLOGY

by
James J. Damron
Geographer
U.S. Army Engineer Research and Development Center
Topographic Engineering Center
Topography, Imagery and Geospatial Research Division
Geospatial Applications Branch
Alexandria, VA 22315-3864
703-428-8168 (work), 703-428-8176 (fax)
jdamron@tec.army.mil

ABSTRACT

Fusing, the merging of traditional cartographic and photogrammetric-derived Digital Elevation Models (DEM), has numerous problems. Problems encountered with merging traditionally derived DEMs are not present in the emerging technologies used in single pass Interferometric Synthetic Aperture Radar (IFSAR) and LIght Detection And Ranging (LIDAR). IFSAR and LIDAR technologies utilize common INU and GPS devices. This makes the merging of DEM data straightforward using any raster-based GIS software package. Problems are encountered when datum, ellipsoid, and geoid models are not documented and supported within a GIS.

        Esri software ArcInfo, with extension ArcGRID, demonstrates how this seven-step methodology can be used by any raster-based GIS software to fuse or merge IFSAR and LIDAR DEMs. This methodology has been tested to provide assistance to the Federal Emergency Management Agency (FEMA) for floodplain mapping. The main goal is to provide a cost-effective mix of wide area coverage with an IFSAR DEM and urban/floodplain coverage with a LIDAR DEM and fuse the two DEMs into one data set. This ongoing work is presented as an applied approach to GIS users involved in floodplain mapping and can be used for other earth science applications.

INTRODUCTION

Digital Elevation Models (DEM) are the primary source of elevation data for the United States and in the rest of the world. At the beginning of the 21st Century, legacy and future DEMs which have been based on outdated documentation methods, must change as datum, ellipsoid, and geoid model information changes. DEM products are not reusable and interoperable over the long term for local, county, and state governments, federal agencies, and end users. The producers of DEM data have not defined or documented DEM data with sufficient information that is critical to maintaining DEM data over long periods of time. Horizontal and vertical datums, ellipsoid and geoid models are usually omitted from the DEM products, three-dimensional (3-D) representations of the earth’s surface, need to be documented with the full 3-D datum name, ellipsoid, and geoid model information. The major premise for this work is that DEMs are not well documented and that the DEM user community will need better information about DEM data in the near future. Thus, users of DEM data should expect GIS and photogrammetric vendors to support 3-D datum information with additional information requirements. DEM data producers document their data with generalized information, however they do not indicate which datum and geoid model was used to obtain orthometric heights for a DEM. Documenting DEM data with all the information needed to maintain the product will make merging or fusing the DEM data easier and will provide for the reuse of DEM data by local, county, and state governments, and federal agencies.

        As part of the objective to provide highly accurate DEM data for FEMA’s Map Modernization Program, two main things have come to the foreground. DEM information contained in delivered DEM products is not adequate to maintain DEM data over long periods of time. As part of this, taxpayers that have funded federal agencies to produce, collect, and purchase DEM data do not have a long-term investment. DEM data are out of date within several years due to better information about the earth’s surface and interior. Taxpayers are not aware of the advancements in datum, ellipsoid, and geoid model information that has taken place over the last twenty-two years. The merging or fusing of multiple DEMs at varying post spacing will be harder without the correct 3-D datum, ellipsoid, and geoid model information. This report will list some of the challenging problems that need to be solved to ensure DEM data of all types become truly interoperable and reusable within the federal government and allow DEM data to be merged or fused correctly within a Geographic Information System (GIS).

DEM FUSION

The main purpose for DEM fusion is to provide a low-cost solution to provide area coverage of urban areas and the flood plain, and wide area coverage outside the urban/floodplain. The wide area coverage would use Interferometric Synthetic Aperture Radar (IFSAR) and the urban/floodplain area would use LIght Detection and Ranging (LIDAR) technologies. The LIDAR and IFSAR DEM data sets would be merged to provide the low-cost solution. The main goal of the seven-step methodology (Damron, 1999) has been to support DEM fusion with any raster-based GIS, Figure 1.

1. ifsarres2 = resample (ifsarclp, 2)
2. Convert IFSAR or LIDAR data from NAVD88 to Ellipsoid heights if needed
3. output1 = con (isnull(nasalidar), 100, nasalidar
4. output2 = setnull (output1 < 50, output1)
5. output3 = (output2 - 100)
6. outmask1 = selectmask (ifsarres2 , output3)
7. mosaic1 = mosaic (outmask1, nasalidar)
Figure 1.  Seven-Step DEM Fusion Methodology


        ArcInfo was used with the ArcGRID extension to demonstrate GIS capabilities for FEMA. The first test took place in1998 using NASA LIDAR data collected during the California El Nino coastal collection of 1998 and IFSAR DEM data that were collected for the California Department of Conservation (CalDOC) (Damron, 1999). The California test was presented at the Applications of Remote Sensing and GIS for Disaster Management Conference held at the George Washington University in Washington, D.C. January 1999. This provided the proof of concept and the seven-step DEM fusion methodology could be applied to other projects by FEMA and the GIS community.

        The second project using the seven-step methodology was with an area surrounding Pembina, North Dakota, near the Canadian border. Commercial IFSAR and LIDAR DEM data sets were purchased for this project. Many deficiencies were found with the available tools within ArcInfo during the investigation. The tools available within ArcInfo merged the LIDAR and IFSAR DEMs, with the use of the GRIDINSERT command. The GRIDINSERT command does several steps involved in the seven-step methodology. One of the major deficiencies of Esri’s ArcInfo was the lack of vertical transformation tools and support for geoid models and the FILL function. In Figure 2, the LIDAR and IFSAR DEMs were merged using the GRIDINSERT command. It shows a vertical offset of the two DEMs along adjoining edges from the northwest top corner to the middle eastern section and from the southeast bottom corner to the middle eastern section. In Figure 3, the same LIDAR and IFSAR DEMs were merged using the GRIDINSERT command with a one meter vertical correction applied to the IFSAR DEM. The vertical offset is not present along adjoining edges and only the LIDAR errors can be detected. The seven-step methodology could not be applied fully within a GIS without support of vertical transformation tools and geoid models. They are needed to get DEM data to ellipsoid heights correctly for the merging process. There were LIDAR data problems associated with this project and to solve future problems with LIDAR data the document titled “FEMA Appendix 4B. Airborne LIght Detection and Ranging Systems” addressed the concerns that materialized during the Red River project.

Figure 2.  LIDAR and Uncorrected IFSAR DEM merged using GRIDINSERT

Figure 2.  LIDAR and Uncorrected IFSAR DEM merged using GRIDINSERT


Figure3.  LIDAR and Corrected IFSAR merged using GRIDINSERT

Figure3.  LIDAR and Corrected IFSAR merged using GRIDINSERT

ARCINFO DEM FUSION PROCESS

Depending on the tools available, the seven-step DEM fusion methodology may be slightly modified with each GIS package. The ArcInfo process is six steps seen in Figure 4. It addresses the datum, ellipsoid, and geoid model transformation process. This process has not been implemented within Environmental Systems Research Institute, Inc. (Esri) ArcInfo due to the lack of vertical transformation tools, geoid model support, and 3-D datums.

        The first step is to import the LIDAR and IFSAR DEMs into ArcInfo. The second step, a decision step, is where the IFSAR and LIDAR datum and geoid models are examined to see if they are in orthometric heights (NAVD 88) or ellipsoid heights. After the determination, the second step branches into two sub determination phases. The first branch determines the geoid model used for the orthometric heights (NAVD 88) and extracts it from the IFSAR and LIDAR DEMs. The second branch determines which datums were used and projects to a common 3-D projection. The third step performs a differencing function on the LIDAR and IFSAR DEMs to determine the separation between the two DEMs. In the third step, GPS data can be used to help in this determination or just use the LIDAR and IFSAR DEMs. Once the separation is determined, a correction is applied to the LIDAR DEM or IFSAR DEM to correct vertical offsets. The fourth step is the DEM fusion. The fourth step uses the GRIDINSERT command to merge the LIDAR and IFSAR DEMs. The fifth step is a DEM accuracy assessment. The GPS data are collected over the area where the LIDAR and IFSAR DEMs overlap at the 2-cm accuracy level, in accordance with the NOAA Technical Memorandum NOS NGS-58 http://www.ngs.noaa.gov:80/PUBS_LIB/NGS-58.html . Statistics are run on the GPS data and the LIDAR/IFSAR DEM to determine level of accuracy. The sixth and final step is a decision step to add a geoid model to the LIDAR/IFSAR DEM to provide orthometric heights (NAVD 88) to the LIDAR/IFSAR DEM. The user requires orthometric heights (NAVD 88), the entire process is finished. This process could be applied to all types of DEM data and works within any GIS.

Figure 4. ArcInfo DEM Fusion Process

Figure 4. ArcInfo DEM Fusion Process

IMPEDIMENTS TO DEM FUSION

The seven-step methodology has limits to what it can do within a GIS. There are several problems associated with GIS capabilities. Some of the other problems areas come from federal agencies not following federal registers when DEM data are purchased, and the documentation of datums, ellipsoid, and geoid model information of the DEM data. The last major problem is support for the full 3-D datum names because newer datums have emerged and will need to be supported within a GIS.

GIS Capabilities

    Geographic Information System (GIS) is a powerful tool for most applications involving the 2-D world. What is the state of support for vertical transformations and the 3-D projections of DEM data? GIS support for horizontal 2-D projection of geospatial data is good, but GIS does not support the vertical transformation and the 3-D projection of DEM data at this moment. In the future, GIS vendors will need to support vertical transformations and the 3-D projection of DEM data that will promote the reuse of DEM data over the long term for all users.
                                       
    Most GIS vendors support raster functionality such as Environmental Systems Research Institute, Inc. (Esri) and ERDAS, Inc. (ERDAS) part of Leica Geosystems. Esri and ERDAS products support the merging or fusing of varying post spaced DEM data. Esri and ERDAS products will allow DEM data to be projected in the horizontal 2-D plain. Three problems are encountered when using GIS software from Esri and ERDAS. One, the two GIS vendors do not recognize the full 3-D datum name, which would help determine the correct transformation and 3-D projection of a DEM. Second, vertical transformations are not based on a straight conversion from NGVD 29 to NAVD 88, but involve a geoid model to obtain the correct NAVD 88 heights for a DEM. Third, the vertical transformation and 3-D projection of DEM data will be computationally intensive.

Federal Registers

    In the United States, two federal registers affirm the official horizontal and vertical datums of our country; and all future United States surveying and mapping activities performed or financed by the Federal Government use them.  Federal Register (Vol. 54, No. 113 page 25318) on June 14, 1989 affirmed the North American Datum of 1983 (NAD 83) as the official horizontal datum for the United States (see Appendix A) and supersedes the North American Datum of 1927 (NAD 27).  Federal Register (Vol. 58, No. 120 page 34245) on June 24, 1993 affirmed the North American Vertical Datum of 1988 (NAVD 88) as the official vertical datum for the United States (see Appendix B) and supersedes the National Geodetic Vertical Datum of 1929 (NGVD 29).

Federal Register (Vol. 60, No. 157 page 42146) August 15, 1995 recommended NAD 83/WGS 84 be used to label all maps and charts’ products that are based on NAD 83 and WGS 84 horizontal datums. One of the most overlooked  pieces of Federal Register (Vol. 60, No. 157 page 42146) severed notice that WGS 84 was realigned with the International Earth Rotation Service's Terrestrial Reference Frame (ITRF) (see Appendix C).

Datums

    Most federal agencies do not follow these two federal registers. This creates problems for the DEM fusion process using GIS. One, federal agencies continue to purchase DEM data based on NAD 27 and NGVD 29 datums. However, these datums are no longer supported within the United States. GIS does not support the vertical transformation of the DEM data to NAVD 88 with the associated geoid model, but GIS does support the 2-D projection of the DEM data to NAD 83. The federal register is not being followed. The mixing of horizontal and vertical datums is common throughout the federal government. A federal agency will purchase a DEM data set in NAD 83 and NGVD 29 datums. Usually, the NAD 83 horizontal datum is associated with the NAVD 88 vertical datum and an NGVD 29 vertical datum is associated with the NAD 27 horizontal datum. This creates a problem for future users of the data when GIS does not support the vertical transformation and 3-D projection of DEM data. DEM data cannot be reused when elevation data are requested this way.

    The only software presently available for GIS users to vertically transform DEM data correctly is the VDatum software. VDatum has been developed and implemented for the region of Tampa Bay, Florida, as part of the joint NOAA/USGS Bathymetric-Topographic Demonstration Project http://chartmaker.ncd.noaa.gov/bathytopo/vdatum.htm . The focus of the Bathymetric-Topographic Demonstration Project http://chartmaker.ncd.noaa.gov/bathytopo is to merge topographic and bathymetric elevation data. VDatum uses the GEOID 99 model to determine NAVD 88 heights. VDatum does support the transformation of DEM products that were produced using older geoid models and transform the elevation data set as ASCII x, y, and z values. The GIS user community needs support of the datums used in the VDatum software to import DEM data in its native format, transform, and merge or fuse different DEM products.

Geoid Models

    The geoid model derives NAVD 88 heights when combined with a DEM that has ellipsoid heights. Due to advances in the study of earth’s gravity the geoid model changes approximately every three years . When a DEM is first created, it is basically locked in time due to the geoid model. Geoid models have changed four times since 1990 when the GEOID 90 model was developed by the National Geodetic Survey (NGS). The GEOID 99 model is the geoid model used today and will soon be updated. The main goal of NGS is to have a 1-cm accuracy geoid model for the United States http://www.ngs.noaa.gov:80/PUBS_LIB/GEOID/GGG2000/ggg2000proc.htm . The geoid model has a certain amount of error associated with the product, and ellipsoid height verification is needed for DEM data. Information on the past and present geoid models used in the United States can be found at http://www.ngs.noaa.gov/GEOID .

Geoid model information is often left out of the documentation of a DEM and for older DEM data sets most the time. A DEM based on NAVD 88 heights cannot be reused when the geoid model is not documented.

METADATA

Metadata of a DEM data set is an important item with IFSAR and LIDAR technologies, and even with photogrammetric derived DEM data. Information from several LIDAR and IFSAR DEM data products examined to determine if they were documented with the correct information. The metadata file from the DEM data products associated with USGS NED, IFSAR, and LIDAR were examined. All of the DEM metadata files meet the Federal Geographic Data Committee (FGDC) requirement.

USGS NED

    The USGS National Elevation Dataset (NED) data are similar to other digital DEM products with metadata. Information on the NED can be found at http://edcnts12.cr.usgs.gov/ned . Once at the NED web site click on About, and select Methodology where information can be found that describes NED production process. Information on the production process used to change the older USGS DEMs based on the NAD 27 and NGVD 29 datums to the NAD 83 and NAVD 88 datums are documented, but a geoid model was not used to produce the orthometric heights for the NAVD 88 vertical datum. Instead, a straight conversion from the NAD 27 and NGVD 29 datums to NAD 83 and NAVD 88 datums was performed using the NGS software NADCON and VERTCON. The United States Army Topographic Engineering Center (TEC) software Corpscon is documented to have been used in this process on the official web page. In the January 2002 issue of the Journal of the American Society for Photogrammetry and Remote Sensing, the NED is explained in the article titled “The National Elevation Dataset” does not document the use of TEC’s Corpscon. The information contained in the article can be found at http://www.asprs.org/asprs/publications/pe&rs/2002journal/january/january_frame.html .

    A NED data set was order from the USGS Geographic Data Download page under the USGS EROS Data Center - Products http://edc.usgs.gov/geodata . Once there, we selected the 30 m NED at the top and then clicked on http link Seamless Data Distribution System (SDDS), then launch to http://edcnts14.cr.usgs.gov/Website/store/viewer.htm .  An area north of Denver, Colorado was selected from this site. In Appendix D, the USGS NED Metadata File for the ordered NED is declared. The geoid model information is missing from the metadata file that documents the NAVD 88 vertical datum because one was never used. If, an end user had the capability to update a NED data set using GIS, this could not be done without a geoid model. Since, the geoid model is not documented, and we know from the web site documentation that a straight conversion took place, and this not documented in the metadata. This important piece of information is missing from the metadata documentation.

IFSAR

    Intermap Technologies, Inc. has a commercial IFSAR system that collects data and produces DEM and imagery products. The system is an active single pass dual SAR system. Intermap’s IFSAR system has day and night with cloud penetration capabilities. Information on IFSAR system can be found at http://www.intermaptechnologies.com .

    Intermap products are sold through the Global Terrain store and are produced in WGS 84 (orig) datum. Information on Intermap DEM and imagery products can be found at www.globalterrain.com. Intermap uses two geoid models to obtain orthometric heights, which is NAVD 88 for the United States. The geoid model used for most United States collections is the GEOID 99. The EGM 96 model is used as part of worldwide products. The Global Terrain DEM products are available in two forms and can be purchased to meet requirements ranging from 0.5 to 3-meter vertical accuracy with a 5-meter post space. The Digital Surface Model (DSM) is the first reflective surface illuminated by the radar sensor and the Digital Terrain Model (DTM) is a proprietary and automated process that produces a bald-earth DEM. Imagery data products referred to as an Orthorectified Radar Image (ORRI) has a pixel size range from 1.25 to 2.5-meters. Additional information can be obtained from Intermap’s Quick Start Guide http://www.globalterrain.com/resources_quickstart_product.html .

    In Appendix E, Older Intermap Metadata File, contains all the required information to update the DEM data. The horizontal datum WGS 84 and ellipsoid model WGS 84 is documented with the GEOID 96 model information. The newer metadata files that Intermap uses are in accordance with the FGDC standards in Appendixes F and G and were delivered in html format. Similar information was found in the older metadata file, which is available in the FGDC metadata format. The confusion is with the FGDC standards. The ellipsoid model documented in Appendix F is actually the geoid model GEIOD 99. The ellipsoid model should be GRS 80. FGDC should improve the way the ellipsoid and geoid models are documented. The information contained in Appendixes F and G is sufficient to know how the data were produced except for the geoid and ellipsoid models confusion.

LIDAR

    There are numerous LIDAR vendors with different sensors, which collect elevation data. Numerous federal agencies are investigating LIDAR technologies. The National Air and Space Administration’s Center for Airborne Remote Sensing and Technology and Applications Development web site lists several vendors with specific sensors at http://carstad.gsfc.nasa.gov/topics/lidarlist.htm . NOAA LIDAR investigations include topographic http://www.ngs.noaa.gov/RESEARCH/RSD/main/lidar/lidar.html and coastal management http://www3.csc.noaa.gov/CSCweb/genericPage.asp?bin=7 . The USGS is involved with LIDAR investigations, which include hydrology, hidden faults, coastal management, and other areas. Information on different commercial LIDAR vendors and sensors can be found at http://www.airbornelasermapping.com/ALMNews.html . Numerous other sites can be found on the World Wide Web (WWW).

Terrapoint and Enerquest were contacted to obtain metadata files from their LIDAR collections. In Appendix H, Terrapoint Metadata File, conforms to the FGDC standards, but the DEM data delivered to the federal agency is in NAD 83 and NGVD 29 datums. The federal agency did not follow the federal registers covered earlier when purchasing the DEM. In Appendix I, Enerquest Metadata File, conforms to the FGDC standard, but the DEM data was delivered in NAD 83 and NGVD 29 datums. The LIDAR vendors are not at fault for the mixing of horizontal and vertical datums. The federal registers are ignored by federal agencies that purchased the data. The data may not be able to be use again without a vertical transformation to NAVD 88.

Ground Control

    The vertical offset of a statewide High Accuracy Reference Network (HARN) could impact LIDAR and IFSAR collections, which use HARNs to provide control for their collection systems tied by GPS. HARNs may not be equal from state to state and this causes problems when merging LIDAR or IFSAR DEMs across state boundaries over large regional areas. LIDAR and IFSAR vendors do not document the GPS or HARN control used by the collection system in the metadata. The control used by the LIDAR and IFSAR collection systems could be used to provide incites into vertical offsets that were may not seem normal for the collection system if the control data was made available in the metadata file. This could be vital information in the near future when a vertical offset is found and a transformation is used on DEM data to correct for a HARN and other related errors.

WORLD GEODETIC SYSTEM 1984

The National Imagery and Mapping Agency (NIMA) formerly known as the Defense Mapping Agency, defines the World Geodetic System 1984 (WGS 84) datum and ellipsoid for the services under the Department of Defense (DoD). WGS 84 has been refined two times, once in 1994 and again in 1996. The two sets of self-consistent GPS realized coordinates (Terrestrial Reference Frames) derived to date have been designated ‘WGS 84 (G730)’ and ‘WGS 84 (G873)’. The ‘G’ indicates these coordinates were obtained through GPS techniques and the number following the ‘G’ indicates the GPS week number when these coordinates were implemented in the NIMA precise ephemeris estimation process (NIMA TR8350.2 and Snay, Soler, 2000).

    The three reference frames for WGS 84 can be stated as WGS 84 (orig.), WGS 84 (G730), and WGS 84 (G873) (Milbert, D.). In part 4 of the Executive Summary, For Geodetic, GIS Data and Other High-Accuracy Applications, defines which WGS 84 reference frames should be used to produce NIMA products. For mapping, charting and navigational users, these improvements are generally negligible. They are most relevant for the geodetic user, GIS, and other high accuracy applications. Thus, modern geodetic positioning within the Department of Defense (DoD) is now carried out in the WGS 84 (G873) reference frame. As additional data become available, NIMA may develop further refinements to the geopotential model and the geocentric reference frame (NIMA TR8350.2).

    In Table 1, the three reference frames with their respective GPS broadcast dates and WGS 84 designations. Federal Register (Vol. 60, No. 157 page 42146) August 15, 1995 also severed notice that WGS 84 was realigned with the International Earth Rotation Service’s Terrestrial Reference Frame (ITRF), which was the WGS 84 (G730) reference frame.

Table 1. WGS 84 Reference Frames

GPS Broadcast Date
Reference Frame
Broadcast GPS orbit from January 29, 1997 to present
WGS 84 (G873)
Broadcast GPS orbit from June 29, 1994 to January 28, 1997
WGS 84 (G730)
Broadcast GPS orbit from January 23, 1987 to June 28, 1994
WGS 84 (orig.)


    WGS 84 (orig.) and NAD 83 (86) can be considered identical for most purposes. In Table 2, WGS 84 (orig.) and NAD 83 (86) are identical horizontally and only slightly different when looking at the flattening coefficient of the ellipsoid models of WGS 84 and GRS 80 (Milbert, D. and GDA Technical Manual).

Table 2. WGS 84 and GRS 80 Ellipsoids

Ellipsoid
Semi-major axis
Inverse flattening
GRS80
6378137 m
298.257222101
WGS84
6378137 m
298.257223563

INTERNATIONAL TERRESTRIAL REFERENCE FRAMES

The International Earth Rotation Service (IERS) was established in 1988 by the International Astronomical Union (IAU)and the International Union of Geodesy and Geophysics (IUGG). The IERS mission is to provide to the worldwide scientific and technical community reference values for Earth orientation parameters and reference realizations of internationally accepted celestial and terrestrial reference systems. The IERS charged to realize, use and promote the International Terrestrial Reference System (ITRS), as defined by the IUGG resolution No. 2 adopted in Vienna, 1991 http://lareg.ensg.ign.fr/ITRF/index-old.html .

    In the geodetic terminology, a reference frame is a set of points with their coordinates (in the broad sense) which realize an ideal reference system. The frames produced by IERS as realizations of ITRS are named International Terrestrial Reference Frames (ITRF). Such frames are all (or a part of) the tracking stations and the related monuments, which constitute the IERS Network, together with coordinates and their time variations http://lareg.ensg.ign.fr/ITRF/index-old.html . A direct connection between WGS 84 (orig.) and NAD 83 (86) were equal when first established. But, with the global networks and the DoD solutions, they have referred themselves to the ITRF geocentric system (Milbert, D.).

WGS 84 and ITRF

    Within the United States, the shifts between WGS 84 (orig.) and WGS 84 (G730) and for NAD 83 (86) to ITRF92 (1994.0) are a little over 2 meters. The shifts between WGS 84 (G730) and WGS 84 (G873) and for ITRF92 (1994.0) to ITRF96 (1997.0) are just a few centimeters (Milbert, D.). In Table 3, the ITRF reference frame and epoch dates is shown. In Table 4, WGS 84 reference frames with equivalent ITRF is shown (Milbert, D.).

Table 3.  ITRF

Reference Frames
Reference Epoch and Dates
ITRF97 (1997.0)
Reference epoch 1997.0, from August 1, 1999 to present
ITRF96 (1997.0)
Reference epoch 1997.0, from March 1, 1998 to July 31, 1999
ITRF94 (1996.0)
Reference epoch 1996.0, from June 30, 1996 to February 28, 1998
ITRF93 (1995.0)
Reference epoch 1995.0,  from January 1, 1995 to June 29, 1996
ITRF92 (1994.0)
Reference epoch 1994.0, from January 9, 1994 to December 31, 1994
ITRF91 (1992.6)
Reference epoch 1992.6, from December 1, 1993 to January 8, 1994
ITRF91 (1988.0)
Reference epoch 1988.0, from August 16, 1992 to December 19, 1992
ITRF90 (1988.0)
Reference epoch 1988.0
ITRF89 (1988.0)
Reference epoch 1988.0
ITRF88 (1988.0)
Reference epoch 1988.0


Table 4. WGS 84 and ITRF

WGS 84 (G873)
ITRF96 (1997.0)
WGS 84 (G730)
ITRF92 (1994.0)
WGS 84 (orig.)
NAD 83 (86)


NAD 83 and ITRF

    The original NAD 83 (86) reference frame has been retained by the United States throughout the years, even though that frame is not geocentric by about 2 meters (Milbert, D.). The United States and Canada have been referencing their network of control to ITRF for many years. The improved realization of NAD 83 (86) in the United States is referred to as NAD 83 (NSRS), where NSRS is an acronym for the National Spatial Reference System. In Canada, it is referred to as NAD 83 (CSRS), where CSRS is an acronym for the Canadian Spatial Reference System (Craymer, Ferland, and Snay, 1999).

    The National Geodetic Survey (NGS) is a part of the larger organization National Oceanic and Atmospheric Administration (NOAA) National Ocean Service within the United States Department of Commerce. The role of NGS is to establish and maintain a network of control. The modernization of this network of control is ongoing, but is an integral part of GIS, Global Positioning System (GPS), LIDAR and IFSAR technologies. The main goal of modernization is to provide monuments that have a 2-cm accuracy using GPS technology.

    The Federal Base Network (FBN) is a very high-accuracy network of permanently marked control points at approximately 1-degree-by-1-degree (75- to 125-km) spacing throughout the United States and its territories (NGS/FBN). NGS are conducting observations to complete the ellipsoidal and orthometric height components of FBN in order to attain coordinate accuracies of 2-cm in three-dimensions (95% confidence level). This task is expected to be completed in 2002 http://www.ngs.noaa.gov/PROJECTS/FBN .

    The Continuously Operating Reference Stations (CORS) is a network of GPS carrier phase and code range measurements in support of three-dimensional positioning activities throughout the United States and its territories http://www.ngs.noaa.gov/CORS . NGS has directly linked NAD 83 coordinates to ITRF using CORS data and NAD 83 to ITRF transformation parameters. The NAD 83 (NSRS) will serve to supercede the conglomeration of regional reference frames that comprise NAD 83 High Accuracy Reference Network (HARN) (Snay, Spoler). This modernization will align NAD 83 (HARN) with the CORS positions.

    Horizontal discrepancies as large as 7 cm exist between NAD 83 (HARN) positions of control points and their idealized NAD 83 (CORS96) positions. Significantly greater discrepancies exist in the vertical dimension, because the accuracy of ellipsoidal heights measured during the earlier HARN surveys compares poorly relative to today’s height-measuring capability across the country. NGS are also developing more and more accurate geoid models to convert such ellipsoidal heights to appropriate orthometric heights (Snay and Spoler, 2000).

CHANGE IS COMING: ITRF FOR THE UNITED STATES

According to Ms. Maralyn Vorhauer (NOAA/NGS), our country is getting ready to adopt a new coordinate system called the ITRF. Ms. Maralyn Vorhauer provided the following information and statement that provide an update to current NGS activities within the United States:

    “Upon completion of the NAD83 (1986) adjustment, GPS quickly began to become established as the preferred surveying method. Just as quickly, it was realized that this method was providing far more accurate results than the network control then available could support without distorting the results.  Therefore, NGS began a state-by-state effort to upgrade the geodetic control network positions using high accuracy GPS surveys (HARNS). The control for these surveys was initially the (what is now called) CORS sites at Westford, MA; Richmond, FL; and Mojave, CA. As a HARN was completed in each state, all of the positions in the state were readjusted to be consistent with the new HARN control. Shifts were in the neighborhood of 1-5 or more decimeters. The status of this effort is that the HARN observations and initial adjustments are complete in all states. The readjustments of the previously observed data is complete in all states except PA (nearly complete), North and South Carolina (both of these states elected not to use the HARN positions), and Alaska (not scheduled to be done for logistical reasons).

    Despite the excellent horizontal positioning results obtained for the HARN surveys, the vertical component remained significantly less accurate. However, by 1998, with the full constellation of satellites in orbit and the increased accuracy of receivers and data reduction techniques, it became possible to improve the vertical component of the National Geodetic Reference System (NSRS) with new observations. This effort was begun with more than 1/2 of the US completed to date. These surveys, called the Federal Base Network (FBN) upgrades, have the objective of improving the vertical component and will also contribute to a new, probably final, full readjustment of all the GPS derived positions in the NSRS in approximately 2005. After that, it is anticipated that the move will be toward using the ITRF as the reference system. In the meantime, as these new FBN surveys are completed,  readjustments are only undertaken if the horizontal or vertical position shifts by more than 5 cm and then only the previously determined GPS values are readjusted in the particular state.

    Thus far, less than six states have needed both the horizontal and vertical components readjusted; nearly all the rest, however, have had all the ellipsoid heights readjusted (i.e., exceeded the 5-cm shift).”

ITRF RELATIONSHIPS WORLDWIDE

    The one unifying worldwide reference frame is ITRF. Most countries of the world have updated or are updating their national datums to ITRF, which include the following countries: Australia, New Zealand, Asian-Pacific countries, South America, Canada, Europe, Middle East, Russia, China, and soon, the United States of America. When someone talks about the ITRF datum worldwide one can associate the GRS 80 ellipsoid with it. As describe by D. Milbert (personnel communications), the relationship between WGS 84, ITRF, and NAD 83 for the United States is seen in Table 4. Support for these new 3-D datums is needed within ArcInfo and other GISes to provide  3-D transformation capabilities for DEM data. Each country also has a new geoid model associated with the update to ITRF.

Table 4. Relationship between WGS 84, ITRF, and NAD 83

WGS 84 <==> ITRF <==> NAD 83


Australia

      The Australian Geodetic Datum 1984 (AGD 84) was used for years in Australia. The new reference frame adopted by Australia is referred to as the Geocentric Datum of Australia 1994 (GDA94), which is based on ITRF92. For all practical purposes, GDA94 and WGS 84 (G870) are the same. The difference is of the order of 10 cm vertically. The GDA uses a more accurate model which is endorsed by the International Association of Geodesy (IAG) and to which WGS 84 reference frame is being aligned referred to as ITRF. Information on the GDA can be found at http://www.anzlic.org.au/icsm/gda .

New Zealand

    New Zealand and Australia adopted the geocentric ITRF datum on January 1, 2000. New Zealand adopted a geocentric datum referred to as the New Zealand Geodetic Datum 2000 (NZGD2000), which is associated with ITRF96 at a reference date of January 1,  2000 (epoch 2000.0) (Land Information New Zealand). The NZGD2000 replaces the New Zealand Geodetic Datum 1949 (NZGD49). Information on the NZGD2000 can be found http://www.linz.govt.nz/rcs/linz/pub/web/root/core/SurveySystem/surveypublications .

Indonesia

    The GEODYSSEA project in South East Asia has aligned the countries of Thailand and Malaysia with ITRF94 (1996.3) and provided transformation parameters from their Indian 1975 national datum. GEODYSSEA is an acronym for GEODYnamics of South and South-East Asia. The ASEAN Partners are BAKOSURTANAL, Cibinong, Indonesia; Dept. of Surveying and Mapping, Kuala Lumpur, Malaysia; Bureau of Energy and Mines, Manila, Philippines; Institute of Geology, National Center for Natural Sciences, Hanoi, Vietnam; Royal Thai Survey Department, Bangkok, Thailand; Department of Public Works, Brunei (Becker, Reinhart, Seeger, Mingsamon, Boonphakee, Abu). For information on the GEODYSSEA project see http://www.ifag.de/Geodaesie/rio/riogeod.htm .

Great Britain and Europe

    Three National Mapping Agencies are responsible for mapping Britain and Ireland, http://www.osmaps.org . The datum of the Ordnance Survey National GPS Network is the European Terrestrial Reference System 1989 (ETRS89), which supercedes the Ordnance Survey Great Britain 1936 (OSGB36) http://www.gps.gov.uk/guidecontents.asp . The ETRS89 coordinate reference system is used throughout Europe http://www.gps.gov.uk/additionalInfo/coordinateSystems.asp . Information on the Europe’s ETRS89 can be found at http://www.euref-iag.org and http://lareg.ensg.ign.fr/EUREF .

South America

    The South American Geocentric Reference System (Sistema de Referencia Geocéntrico para América del Sur, SIRGAS) Project was established to define a new reference system based on ITRF94 as the South American Geocentric Datum. A transformation from the old datums (e.g. the Provisional South American Datum 1956, PSAD 56, or the South American Datum 1969, SAD 69) to the new SIRGAS datum is possible (Drewes). Information on the SIRGAS Project can be found at http://dgfi2.dgfi.badw-muenchen.de/dgfi/SIRGAS/sirgas.html and at http://www.gfy.ku.dk/~iag/Travaux_99/sirgas.htm .

A NATIONAL ELLIPSOID DATASET

Why does the United States need a national DEM data set based on ellipsoid heights? In a national emergency, high resolution NIMA Digital Terrain Elevation Data (DTED®) based on ellipsoid heights using the WGS 84 (org.) datum and USGS NED data based on a vertical datum NAVD 88 could not be merged to produce an accurate DEM data set of an area within a GIS because of the vertical offset of USGS NED. The merged DTED® and NED data set could be offset vertically by as much as several meters.

    DEM data for the United States stored using ellipsoid heights and a common projection would provide users with a consistent DEM data set not based on the NAVD 88 vertical datum. Geoid model information could be added later by the GIS user when orthometric heights are needed. This would eliminate a need to update the nations DEM data when the geoid model or the datum changes. The USGS will have two options when the United States switches to ITRF. It could update the NED data to ITRF as ellipsoid heights only or continue to produce the NED based on orthometric heights (NAVD 88). The first option would be better over the long term for the country. This issue has not been discussed within the National Digital Elevation Program (NDEP) http://www.ndep.gov which could decide the best course of action for the nation with standards and guidelines that federal agencies would follow when they purchase DEM data.

CONCLUSIONS

The seven-step methodology does work as long as GIS supports the true 3-D nature of DEMs. DEMs from various sources need some type of vertical transformation and 3-D projection in the near future. Esri’s ArcInfo is presently not capable of the full implementation of the seven-step methodology, and needs to support the newer 3-D datums and vertical transformations similar to the VDatum software. Without the critical support of full 3-D datum names, ellipsoid, and geoid models GIS users will not be able to import, tranform or project, and merge or fuse DEM products from various sources such as LIDAR and IFSAR technologies correctly.

    DEM data are an important source of elevation information. Federal agencies continue to ignore federal registers that stated the NAD 83 and NAVD 88 datums are to be used for surveying and mapping activities within the federal government. This has led to DEM data purchases and holdings by federal agencies that are based on the legacy NAD 27 and NGVD 29 datums and mixed horizontal and vertical datums NAD 83 and NGVD 29. These legacy datums and the incompatible mixing of horizontal and vertical datums will continue to cause problems for GIS users within the federal government. Federal agencies need to purchase DEM data in a standard format and datums following the federal registers, which would be based on ellipsoid heights in the near future.

    The support for the full name of a datum is needed to assist in this long term goal of interoperable DEM products. Datums used by DoD for high accuracy mapping and GIS activities have changed over the years. The new WGS 84 reference frames WGS 84 (G730) and WGS 84 (G873) are not supported within a GIS because of the vertical component being based on ITRF. The WGS 84 reference frames based on ITRF will continue to change over time. Legacy and incompatible datums used by other federal agencies need to be ready for the coming change of the new datum ITRF. The ITRF will mean a 1- to 2-meter horizontal and approximately 2-meter vertical change for the United States. Worldwide ITRF is the unifying datum. Most of the countries of the world have updated or are in the process of updating to an ITRF-based national datum.

    The information contained in a metadata file of a DEM product, as well as the header file, is important to the long term use of the DEM data. The FGDC metadata file used to document LIDAR, IFSAR, and other DEM products needs to be updated to support the full name of the datum, ellipsoid, and geoid model used. The most needed correction to the documentation of the metadata file for DEM products based on IFSAR and LIDAR technologies are the geoid model and ground control. Without the geoid model and ground control information, future transformations cannot be applied to LIDAR and IFSAR DEMs.

Esri, other GIS software producers, and the DEM community need to support full 3-D datum names, ellipsoid, and geoid model information, including the 3-D projection and vertical transformation of DEM data. GIS software producers need to see DEM data as 3-D data products instead of as 2-D products. When GIS software producers finally achieve 3-D support of DEM products, such as with the VDatum software, numerous sources of DEM data, such as LIDAR, IFSAR, USGS NED, and other products can be imported, transformed, and merged or fused within a GIS to record changes and to support activities by FEMA and other federal agencies.

ACKNOWLEDGMENTS

I would like to thank Ms. Maralyn Vorhauer, Dr. Dennis Milbert, and Dr. Dru Smith of  NOAA/NGS for contributions to this report. Without their help and information, the modernization of DEM data within a GIS could not be possible.

REFERENCES

(Unless otherwise indicated, all internet data were accessed in May 2002.)

Becker, M., Reinhart, E., Seeger, H., Mingsamon, S., Boonphakee, C., and Abu, S. “Realization of the ITRF-94 in Thailand and Malaysia by Use of A Combined Network for Geodynamics”, Bundesamt für Kartographie und Geodäsie (BKG) (Federal Agency for Cartography and Geodesy), Germany, http://www.ifag.de/Geodaesie/rio/riogeod.htm , March 20, 1998.

Craymer, M., Ferland, R., and Snay, R. “Realization and unification of NAD83 in Canada and the U.S. via the ITRF”, Towards an Integrated Global Geodetic Observing System (IGGOS), IAG Section II Symposium, Munich, October 5-9, 1998, Revised 11 March 1999, International Association of Geodesy Symposia, Vol. 120, Springer, Berlin, http://www2.geod.nrcan.gc.ca/~craymer/nets/nad83csrs/nad83csrs.html .

Damron, James. “Techniques for Digital Elevation Model (DEM) Fusion Using ARC/INFO GRID: Using IFSAR and LIDAR DEM Data”, Applications of Remote Sensing and GIS for Disaster Management Conference, Washington, D.C., George Washington University January 19-21, 1999.

Damron, J., and Daniel, C. “Central California Valley IFSAR Collection”, Topographic Engineering Center ERDC/TEC LR-00-1, http://www.tec.army.mil/info_pubs.html , March 2000.

Damron, James. “Generating A Coastal Boundary and Merging Bathymetry with DTED® Level 1 Using ArcInfo: A Modeling and Simulation Application”, Topographic Engineering Center ERDC/TEC TN-00-1, http://www.tec.army.mil/info_pubs.html , June 2000.

Damron, J., and Daniel, C. “Evaluating IFSAR and LIDAR Technologies Using ArcInfo: Red River Pilot Study”, Topographic Engineering Center ERDC/TEC TR-01-2, http://www.tec.army.mil/info_pubs.html , July 2000.

Deutsches Geodaetisches Forschungsinstitut. “SIRGAS (Sistema de Referencia Geocentrico para America del Sur)”, Muenchen, Germany, http://dgfi2.dgfi.badw-muenchen.de/dgfi/SIRGAS/sirgas.html

Director of Surveys. “Introduction to NAD83(CSRS) Fact Sheet - Fact Sheet 5 of 8 , Geodetic Control Unit, Publications/Forms, Director of Surveys, Government of Alberta, Canada, http://www3.gov.ab.ca/srd/land/dos/GSPub.html , December 2001.

Director of Surveys. “Impact of NAD83(CSRS) Adoption Fact Sheet - Fact Sheet 6 of 8 , Geodetic Control Unit, Publications/Forms, Director of Surveys, Government of Alberta, Canada, http://www3.gov.ab.ca/srd/land/dos/GSPub.html , December 2001.

Drewes, Hermann. “Report on the South American Geocentric Reference System (SIRGAS)”, IAG Representative in the SIRGAS project, Deutsches Geodaetisches Forschungsinstitut, Muenchen, Germany, http://www.gfy.ku.dk/~iag/Travaux_99/sirgas.htm , 1999.

Garrard, G., and Junkins, D. “Demystifying Reference Systems: A Chronicle of Spatial Reference Systems in Canada”, Geodetic Survey Division, Geomatics Canada, Natural Resources Canada (NRCan), SDI 1998 Conference, Ottawa, Ontario, Canada, Canadian Institute of Geomatics Geomatica, Volume 52, Number 4, 1998, http://www2.geod.nrcan.gc.ca:80/~craymer/pubs/datums_geomatica98.pdf , June 1998.

Gesch, D., Oimoen, M., Greenlee, S., Nelson, C., Steuck, M., and Tyler, D. “The National Elevation Dataset”, Journal of the American Society for Photogrammetry and Remote Sensing, Photogrammetric Engineering & Remote Sensing (PE&RS), Volume 68, Number 1, http://www.asprs.org/asprs/publications/pe&rs/2002journal/january/january_frame.html , January 2002.

Inter-governmental Committee on Surveying and Mapping. “Get In Step With the Geocentric Datum - Discussing the Business Issues”, http://www.anzlic.org.au/icsm/gda/brochcontent.htm , 1999.

Inter-governmental Committee on Surveying and Mapping. “What is the difference between WGS84 and GDA94?, http://www.anzlic.org.au/icsm/gda/brochcontent.htm , April 2, 2001.

Inter-governmental Committee on Surveying and Mapping. “Geocentric Datum of Australia Technical Manual Version 2.2”, http://www.anzlic.org.au/icsm/gdatm/ , February 11, 2002.

Kouba, J., and Popelar, J. “Modern Geodetic Reference Frames For Precise Satellite Positioning and Navigation”, Geodetic Survey Division, Geomatics Canada, Natural Resources Canada (NRCan), http://www.geod.nrcan.gc.ca:80/site/index_e/products_e/publications_e/papers_e/kouba.pdf , October 18, 2001.

Land Information New Zealand. “New Zealand Geodetic Datum 2000 (NZGD2000)”, http://www.linz.govt.nz/rcs/linz/pub/web/root/core/SurveySystem/surveypublications , August 1998.

Land Information New Zealand. "Realisation of the New Zealand Geodetic Datum 2000", Office of the Surveyor-General (OSG) Technical Report Number 5, http://www.linz.govt.nz/rcs/linz/pub/web/root/core/SurveySystem/surveypublications , June 1, 2000.

Milbert, Dennis.  “A Tutorial on Datums”, National Geodetic Survey, National Ocean Service, NOAA, http://chartmaker.ncd.noaa.gov/bathytopo/DennisWeb/tutor.doc .

Milbert, Kathryn. “An Evaluation of the High Accuracy Reference Network Relative to the Continuously Operating Reference Stations”, National Geodetic Survey, National Ocean Service, NOAA, http://www.ngs.noaa.gov:80/PUBS_LIB/HARN_CORS_COMP/eval_harn_to_cors.html .

National Geodetic Survey. “Affirmation of Datum for Surveying and Mapping Activities”, Index of On Line Publications, Federal Register Notices, NOAA/NGS, http://www.ngs.noaa.gov:80/PUBS_LIB/pub_index.html , June 13, 1989.

National Geodetic Survey. “Affirmation of Vertical Datum for Surveying and Mapping Activities”, Index of On Line Publications, Federal Register Notices, NOAA/NGS, http://www.ngs.noaa.gov:80/PUBS_LIB/pub_index.html , June 23, 1993.

National Geodetic Survey. “Use of the NAD 83/WGS 84 Datum Tag on Mapping Products”, Index of On Line Publications, Federal Register Notices, NOAA/NGS, http://www.ngs.noaa.gov:80/PUBS_LIB/pub_index.html , August 14, 1995.

National Geodetic Survey. “The Federal Base Network - What is an FBN Survey?”, NOAA/NGS, http://www.ngs.noaa.gov/PROJECTS/FBN/index.htm , July 2000.

National Imagery and Mapping Agency. "Department of Defense World Geodetic System 1984, Its Definition and Relationships With Local Geodetic Systems",  NIMA Technical Report 8350.2, Third Edition, Amendment 1, http://164.214.2.59/GandG/tr8350_2.html , January 3, 2000.

Roman, D., and Smith, D. “Recent Investigations Toward Achieving a One Centimeter Geoid”, NOAA/NGS, http://www.ngs.noaa.gov:80/PUBS_LIB/GEOID/GGG2000/ggg2000proc.htm .

Snay, R., and Soler, T. “Part 1 - Modern Terrestrial Reference Systems”, Professional Surveyor, 19(10), 32-33, NOAA/NGS, CORS GeneralInformaiton/Articles, http://www.ngs.noaa.gov/CORS/Articles/Reference-Systems-Part-1.pdf , 1999.

Snay, R., and Soler, T. “Part 2 - The evolution of NAD83 , Professional Surveyor, 20(2), 16, 18, NOAA/NGS, CORS GeneralInformaiton/Articles, http://www.ngs.noaa.gov/CORS/Articles/Reference-Systems-Part-2.pdf , 2000.

Snay, R., and Soler, T. “Part 3 - WGS 84 and ITRS” Professional Surveyor, 20(3), 24, 26, 28, NOAA/NGS, CORS GeneralInformaiton/Articles, http://www.ngs.noaa.gov/CORS/Articles/Reference-Systems-Part-3.pdf , 2000.

Snay, R., and Soler, T. “Part 4 - Practical considerations for accurate positioning”, Professional Surveyor, 20(4), 32-34, NOAA/NGS, CORS GeneralInformaiton/Articles, http://www.ngs.noaa.gov/CORS/Articles/Reference-Systems-Part-4.pdf , 2000.

Appendix A.  Affirmation of Datum for Surveying and Mapping Activities

25318             Federal Register / Vol. 54, No. 113 / Wednesday. June 14, 1989 / Notices
 
Affirmation of Datum for Surveying and Mapping Activities
 
AGENCY: National Oceanic and Atmospheric Administration, National Ocean Service, Charting and Geodetic Services.
 
ACTION: Notice.
 
SUMMARY: The Office of Charting and Geodetic Services (C&GS). National Geodetic Survey Division. has completed the redefinition and readjustment of the North American Datum of 1927 (NAD 27), creating the North American Datum of 1983 (NAD 83). The interagency Federal
Geodetic Control Committee (FGCC) affirmed NAD 83 is the official civilian horizontal datum for U.S. surveying and mapping activities performed or financed by the Federal Government. Furthermore, to the extent practicable, legally allowable and feasible, all Federal agencies using or producing coordinate information should provide for an orderly transition from NAD 27 to NAD 83.
 
FOR FURTHER INFORMATION CONTACT: Mr. James E. Stem, N/CG1x4, Rockwall Building, Room 619, National Geodetic Survey, NOAA, Rockville.
Maryland 20852; phone: (301) 443-8749.
 
SUPPLEMENTARY INFORMATION: A Federal Register notice published on June 29,1979 (FR Doc. 79-20169, Vol. 44, No. 127) by the National Oceanic and Atmospheric Administration provided notice of the establishment of a new Datum (NAD 83) to which the geographic and plane coordinate values for the National Network of Horizontal Geodetic Control would be referenced. For all published horizontal stations in the National Geodetic Reference System. NAD 83 values of geodetic position (latitude and longitude), and all subsequently derived plane coordinates are available from the National Ocean Service /National Geodetic Survey Division. For a discussion of the plane coordinate systems published, see the "Policy on Publication of Plane Coordinates" in FR Doc. 77-8847, Vol. 42, No. 57, March 24,1977. The FGCC. chaired by the Director. C&GS, is mandated by the Office of Management and Budget to coordinate geodetic surveying performed or financed by the Federal Government.
 
Dated: June 2,1989.
Thomas 1. Maginnis,
Assistant Administrator for Ocean Services and Coastal Zone Management. NOAA.
[FR-Doc. 89--14076 Filed 6-13-89; 8:45 am]
BILLING CODE 3510-08-M

Appendix B.  Affirmation of Vertical Datum for Surveying and Mapping Activities

Federal Register / Vol. 58, No. 120 / Thursday. June 24, 1993 / Notices             34245
 
[Docket No. 930650-3150]
 
Affirmation of Vertical Datum for Surveying and Mapping Activities
 
SUBAGENCY: National Ocean Service, Coast & Geodetic Survey. National Oceanic and Atmospheric Administration, DOC.
 
ACTION: Notice.
 
SUMMARY: This Notice announces a decision by the Federal Geodetic Control Subcommittee (FGCS) to affirm the North American Vertical Datum of 1988 (NAVD 88) as the official civilian vertical datum for surveying and mapping activities in the United States performed or financed by the Federal Government. and to the extent practicable, legally allowable, and feasible, require that all Federal agencies using or producing vertical height information undertake an orderly transition to NAVD 88.

FOR FURTHER INFORMATION CONTACT. Mr. James & Stem, N/CG1x4, SSMC3, Station 9357, National Geodetic Survey. NOAA, Silver Spring,
Maryland 20910; telephone: 301-713-3230.

SUPPLEMENTARY INFORMATION The Coast and Geodetic Survey (C&GS), National Geodetic Survey (NGS), has completed the general adjustment portion of the NAVD 88 project, which includes approximately 80 percent of the previously published bench marks in the NGS data base. The remaining "posted" bench marks which comprise approximately 20 percent of the total will be published by October 1993. Regions of significant crustal motion will be analyzed and published as resources allow. NAVD 88 supersedes the National Geodetic Vertical Datum of 1929 (NGVD 29) which was the former official height reference (vertical datum) for the United States. NAVD 88 provides a modem, improved vertical datum for the United States, Canada, and Mexico. The NAVD 88 heights are the result of a mathematical least squares general adjustment of the vertical control portion of the National Geodetic Reference System and include 80,000
km of now U.S. Leveling observations undertaken specifically for this project. NAVD 88 height information in paper or digital form is available from the National Geodetic Information Branch, N/CG174, SSMC3, Station 9202, National Geodetic Survey. NOAA, Silver Spring, Maryland, 20910; telephone: 301-713-3242.
 
Dated: June 21, 1993.
W. Stanley Wilson,
Assistant Administrator for 0cean Services and Coastal Zone Management, NOAA.
[FR Doc. 93-14922 Filed 6-23--93; 8:45 am)
BILLING CODE 351

Appendix C.  Use of the "NAD / GWS 84" Datum Tag on Mapping Products

42146             Federal Register / Vol. 60, No. 157 / Tuesday, August 15, 1995 / Notices

National Oceanic and Atmospheric Administration

[Docket No. 950728196--5196-011

Use of the "NAD / GWS 84" Datum Tag on Mapping Products [Note error: GWS should be WGS.]

AGENCY: Office of National Geodetic Survey, National Ocean Service, National Oceanic and Atmospheric Administration, Commerce.

ACTION: Notice.

SUMMARY: The Office of National Geodetic Survey, redefined and readjusted the North American Datum of 1927 (NAD 27), creating the North American Datum of 1983 (NAD 83). The World Geodetic System of 1984 (WGS 84) was defined by the Defense Mapping Agency (DMA). The interagency Federal Geodetic Control Subcommittee (FGCS) at its meeting on December 7, recommended that "All maps and charts produced for North America, at scales of 1:5,000 or smaller, that are based on either the North American Datum of 1983 (NAD 83) or the World Geodetic System of 1984 (WGS 84), should have the horizontal datum labeled as NAD 83/WGS 84".

SUPPLEMENTARY INFORMATION: The following supplementary information was reviewed by FGCS membership. A Federal Register notice published on June 29, 1979 (44 FIR 37969), by the National Oceanic and Atmospheric Administration (NOAA) provided notification of the establishment of a new Datum (NAD 83) to which the geographic and plane coordinate values for the National Network of Horizontal Geodetic Control would be referenced. A Federal Register notice published on June 14,1989 (54 FR 25318), by NOAA affirmed NAD 83 as the official horizontal datum for all future U.S. surveying and mapping activities performed or financed by the Federal Government. Furthermore, this notice said that to the extent practicable and feasible, all Federal agencies using coordinate information should provide for an orderly transition to NAD 83.

Both NAD 83 and WGS 84 were originally defined (in words) to be geocentric and oriented as the Bureau International de I'Heure (BIH) Terrestrial System. In principle, the three-dimensional coordinates of a single physical point should therefore be the same in both NAD 83 and WGS 84 systems; in practice, small differences are sometimes found. The original intent was that both systems would use the Geodetic Reference System of 1980 (GRS 80) as a reference ellipsoid. As it happened, the WGS 84 ellipsoid differs very slightly from GRS 80. The difference is 0.0001 meters in the semi-minor axis.
 
Effective January 2, 1994, the WGS 84 reference system was realigned to be compatible with the International Earth Rotation Service's Terrestrial Reference Frame (ITRF).

FOR FURTHER INFORMATION CONTACT: Mr. James E. Stem, N/CG11, SSMC3 Station 9357, National Geodetic Survey, NOAA, Silver Spring,
Maryland 20910; telephone: (301) 713-3231, FAX: (301) 713-4176, Internet: jstem@ngs.noaa.gov.

Dated: July 5, 1995.
W. Stanley Wilson,
Assistant Administrator, NOS.
[FR Doc. 95-19408 Filed 8-14-95; 8:45 am]
BILLING CODE 3510-08-M

Appendix D.  USGS NED Metadata File

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Identification_Information:
  Citation:
    Citation_Information:
      Originator: U.S. Geological Survey (USGS), EROS Data Center
      Publication_Date: 1999
      Title: National Elevation Dataset
      Edition: 1
      Geospatial_Data_Presentation_Form: raster digital data
      Publication_Information:
        Publication_Place: Sioux Falls, SD
        Publisher: U.S. Geological Survey
      Online_Linkage: http://edcnts12.cr.usgs.gov/ned/ned.html
  Description:
    Abstract:
      The USGS National Elevation Dataset (NED) has been developed by
      merging the highest-resolution, best-quality elevation data available
      across the United States into a seamless raster format. NED is the result
      of the maturation of the USGS effort to provide 1:24,000-scale Digital
      Elevation Model (DEM) data with NAD83 datum for the conterminous
      US and Hawaii, and 1:63,360-scale DEM data with NAD27 datum for Alaska.
    Purpose:
      Geospatial elevation data are utilized by the scientific and resource
      management communities for global change research, hydrologic modeling,
      resource monitoring, mapping, and visualization applications.
    Supplemental_Information:
      (Source DEM information)
Only 24 Metadata records are currently included in the Dynamic Metadata.  The bounding coordinates requested include more than 24 records so this metadata is the generic metadata for the whole dataset.  Time_Period_of_Content:
    Time_Period_Information:
      Range_of_Dates/Times:
        Beginning_Date: 19990201
        Ending_Date: Unknown
    Currentness_Reference: publication date
  Status:
    Progress: In work
    Maintenance_and_Update_Frequency: As needed
  Spatial_Domain:
    Bounding_Coordinates:
      West_Bounding_Coordinate:-105.5263888889
      East_Bounding_Coordinate:-104.9844444444
      North_Bounding_Coordinate:40.01944444444
      South_Bounding_Coordinate:39.48111111111
  Keywords:
    Theme:
      Theme_Keyword_Thesaurus: GCMD Parameter Keywords
      Theme_Keyword: EARTH SCIENCE
      Theme_Keyword: LAND SURFACE
      Theme_Keyword: TOPOGRAPHY
      Theme_Keyword: LANDFORMS
      Theme_Keyword: TERRAIN ELEVATION
      Theme_Keyword: 1-DEGREE DEM
      Theme_Keyword: 2-ARC-SECOND DEM
      Theme_Keyword: 7.5-MINUTE DEM
      Theme_Keyword: CARTOGRAPHY
      Theme_Keyword: DEM
      Theme_Keyword: DIGITAL ELEVATION MODEL
      Theme_Keyword: DIGITAL MAPPING
      Theme_Keyword: EDC
      Theme_Keyword: EROS
      Theme_Keyword: GEODATA
      Theme_Keyword: GIS
      Theme_Keyword: MAPPING
      Theme_Keyword: RASTER
      Theme_Keyword: USGS
    Place:
      Place_Keyword_Thesaurus: GCMD Location Keywords
      Place_Keyword: NORTH AMERICA
      Place_Keyword: UNITED STATES
      Place_Keyword: UNITED STATES OF AMERICA
  Access_Constraints: None
  Use_Constraints:
    None.  Acknowledgement of the originating agencies would be appreciated
    in products derived from these data.
Spatial_Data_Organization_Information:
  Direct_Spatial_Reference_Method: Raster
Distribution_Information:
  Distributor:
    Contact_Information:
      Contact_Person_Primary:
        Contact_Person: Customer Services Representative
        Contact_Organization: EROS Data Center
      Contact_Address:
        Address_Type: mailing and physical address
        Address:
          U.S. Geological Survey
          EROS Data Center
        City: Sioux Falls
        State_or_Province: SD
        Postal_Code: 57198
        Country: USA
      Contact_Voice_Telephone: 605-594-6151
      Contact_Facsimile_Telephone: 605-594-6589
      Contact_Electronic_Mail_Address: custserv@edcmail.cr.usgs.gov
  Resource_Description: National Elevation Dataset (NED)
  Distribution_Liability:
    Although these data have been processed successfully on a computer
    system at the U.S. Geological Survey, EROS Data Center, no warranty
    expressed or implied is made by either regarding the utility of the
    data on any system, nor shall the act of distribution constitute any
    such warranty.  The USGS will warrant the delivery of this product in
    computer-readable format and will offer appropriate adjustment of
    credit when the product is determined unreadable by correctly adjusted
    computer peripherals, or when the physical medium is delivered in
    damaged condition.  Requests for adjustments of credit must be made
    within 90 days from the date of this shipment from the ordering site.
Metadata_Reference_Information:
  Metadata_Date: 19990211
  Metadata_Contact:
    Contact_Information:
      Contact_Person_Primary:
        Contact_Person: Customer Services Representative
        Contact_Organization: EROS Data Center
      Contact_Address:
        Address_Type: mailing and physical address
        Address:
          U.S. Geological Survey
          EROS Data Center
        City: Sioux Falls
        State_or_Province: SD
        Postal_Code: 57198
        Country: USA
      Contact_Voice_Telephone: 605-594-6151
      Contact_Facsimile_Telephone: 605-594-6589
      Contact_Electronic_Mail_Address: custserv@edcmail.cr.usgs.gov
  Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata
  Metadata_Standard_Version: FGDC-STD-001-1998

Appendix E. Older Intermap Metadata File

Intermap Technologies Inc.
Global Terrain Metadata File (DEM)

  File Creation date:            Wednesday, June 02, 1999
  Tile Identifier #:            GT1N36W075F8V1.bil
  Project Area:                Virginia Beach

  Product Description
  Product Level:            GT1
  DEM posting (meters):        5.0
  Horizontal Accuracy:            2.5 meters (1 sigma)
  Vertical Accuracy:            3 meters (1 sigma)

  Sensor
  Data Source:                Intermap Star-3i Airborne Interferometric SAR
  Flying Height:            20,000 ft. Above Mean Ground
  Primary Look:            West
  Alternate (Secondary)Look:        South
  Mission #(s):                165
  Acquisition Date:            3/10/99
  Band:                    X-Band

  Processing
  Interpolation:                Continuous curvature spline over non-data areas
  Phase Unwrapper:            Goldstein

  Data Format, Parameters, and Coordinates
  Format:                32 bit BIL (float)
  Projection:                UTM
  Horizontal Datum:            WGS-84 Ellipsoid
  Vertical Datum:            WGS-84 Ellipsoid
  Geoid Model:                GEOID96
  Vertical Reference:            Mean Sea Level (MSL)
  Central Scale:                0.9996
  UTM Zone:                18
  Central Meridian:            75 degrees West
  False Easting (meters):        500,000.0 meters
  False Northing (meters):        0.0 meters
  UTM Easting (meters):        Min.    410,027.50   Max.    419,197.50
  UTM Northing(meters):        Min.  4,059,202.50   Max.  4,067,862.50
  Pixel Origin:                Center Center
  Pixels (columns):            1835
  Lines (rows):                1733

  Legacy Information
  Intermap Project Number:        98063
  Flight Acquisition Manager:        J. Keith Tennant    403.266.0900
  Denver Processing Center:        Ken Rath        303.708.0955
  Ottawa Processing Center:        Ian Isaacs        613.226.5442
  Metadata File Creator:        Tom Hutt        613.226.5442
  Mississippi DHS Center:        Ron Birk        228.688.1465
  Project Manager:            Henry Gansen        613.226.5442
  Metadata File Description:        www.globalterrain.com
  Intermap Information:            www.intermaptechnologies.com
  ISO 9001 Certification No. 0411-069

Appendix F.  Intermap GLOBAL Terrain: "hara2nwmhb.bil"

GLOBAL Terrain: "hara2nwmhb.bil"

Metadata also available as - [ Parseable text ] - [XML ]

Metadata:


Identification_Information:
Citation:
Citation_Information:
Originator: Intermap Technologies Inc.
Publication_Date: 20011220
Title: GLOBAL Terrain: "hara2nwmhb.bil"
Edition: 1
Geospatial_Data_Presentation_Form: Digital Elevation Model
Series_Information:
Series_Name: GLOBAL Terrain Digital Surface Models
Issue_Identification: Version 1
Publication_Information:
Publication_Place: Englewood, CO
Publisher: Intermap Technologies Inc.
Online_Linkage: <URL:http://www.globalterrain.com>
Online_Linkage: <URL:http://www.intermaptechnologies.com>
Online_Linkage: <URL:http://www.globalterrain.com/gt.asp#Product Handbook>
Description:
Abstract:
This data set is a digital elevation model (DEM) product that populates the GLOBAL Terrain product catalog. The DEM products are generated using the Intermap STAR-3 i airborne interferometric synthetic aperture radar (SAR) system mounted in a LearJet 36A aircraft.

The nominal GLOBAL Terrain Digital Elevation Model (DEM) data files are digital representations of cartographic information in a grid form. DEMs consist of a sampled array of elevations for a number of ground positions at regularly spaced intervals. These digital data files are produced by Intermap Technologies Inc.(Intermap) as part of the GLOBAL Terrain product line and are licensed in 7.5-minute tiles for areas located between 0 and 56 degrees North/South. Data for locations above 56 degrees North/South are licensed in 15-minute by 7.5-minute tiles.

GLOBAL Terrain DEM products represent the first reflective surface as illuminated by the radar. Accuracy statements are based on areas of moderate terrain. Diminished accuracies are to be expected in areas of extreme terrain and dense vegetation.

The nominal GLOBAL Terrain Digital Terrain Model (DTM) data files are digital representations of cartographic information in a grid form after the application of Intermap's proprietary system known as 'Terrain Fit'. Terrain Fit removes high frequency variations found in the first reflective surface DEM. This effectively removes elevation posts of features such as manmade structures, isolated trees, ecetera that have a relatively small footprint. Having removed these features the final regular posted DTM is derived through interpolation of the remaining elevation posts.

GLOBAL Terrain DEMs are produced within four classes of vertical accuracy. GTF DEMs have an accuracy of 0.5m Root Mean Square Error (RMSE) or better. GT1 DEMs have an accuracy of 1.0m RMSE or better. GT2 DEMs have an accuracy of 2.0m RMSE or better. GT3 DEMs have an accuracy of 3.0 RMSE or better. No in-scene ground control points are required for GT2 and GT3 products provided that the DGPS ground station is within 200 km of the data acquisition area. The GTF and GT1 products do require in-scene ground control.

The DEM data for 7.5-minute units correspond to the USGS 1:24,000 and 1:25,000 scale topographic quadrangle map series for available areas in the United States and throughout the world. Each 7.5-minute DSM is based on 5- by 5-meter, or 10- by 10-meter post spacing using the Universal Transverse Mercator (UTM) projection. Each 7.5- by 7.5-minute tile provides full coverage with overlap into adjacent tiles.

Purpose:
The purpose of this data set is to provide a source for current and accurate digital elevation models with vertical accuracy of between 0.5 meter and 3 meters and post spacing of 5 or 10 meters.

The DEMs are used as a fundamental layer of information in Geographic Information Systems (GIS) and Spatial Information Decision Support Systems (DSS). A number of the priority layers of spatial information recognized by the National Spatial Data Infrastructure may be derived from GLOBAL Terrain DEMs, including elevation, hydrography, slope, aspect, and shoreline delineation.

Supplemental_Information:
The STAR-3 i system employs three principle technologies: X-band Horizontal -Horizontal (HH) polarized SAR, a ring laser-based inertial measurement unit (IMU), and Differential Global Positioning System (DGPS). STAR-3i was developed by the Environmental Research Institute of Michigan (ERIM) under contract to the U.S. Defense Advanced Research Projects Agency (DARPA).

The system is comprised of two X-band radar antennae that collect data simultaneously. The set of acquired data are "interfered" by a digital correlation process to extract terrain height data and geometrically correct radar images. STAR-3 i uses post-processed DGPS data, together with precise inertial measurement data, to attain highly accurate positioning control. Precise terrain height and positioning data are enhanced by careful calibration of the baseline separating the two antennae.

The STAR-3 i system accuracy has been independently validated by tests conducted by the U.S. Army Topographic Engineering Center, the Institute of Navigation, Stuttgart University and by NASA. A summary of test results are accessible at <URL:http://www.globalterrain.com> .

The GLOBAL Terrain folder name describes the geographic location of a tile. The GLOBAL Terrain file name encapsulates the GT processing level and the product version number. A complete explanation of the GLOBAL Terrain file name can be found in the GLOBAL Terrain Product Handbook. <URL:http://www.globalterrain.com/gt.asp#Product Handbook> .

Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 20010801
Ending_Date: 20010803
Currentness_Reference:
The above dates refer to the time of field data acquisition and therefore reflect ground conditions at that time.
Status:
Progress: Complete
Maintenance_and_Update_Frequency: Ongoing
Spatial_Domain:
Bounding_Coordinates:
West_Bounding_Coordinate: -150.9000
East_Bounding_Coordinate: -151.2000
North_Bounding_Coordinate: 70.2500
South_Bounding_Coordinate: 70.1250
Keywords:
Theme:
Theme_Keyword_Thesaurus: MEL_Scientific-Engineering_Field_Thesaurus
Theme_Keyword: Elevation
Theme_Keyword: Cartography
Theme_Keyword: Geodesy
Theme_Keyword: Geography
Theme_Keyword: Hypsography
Theme_Keyword: Mapping
Theme_Keyword: Photogrammetry
Theme_Keyword: Stereophotogrammetry
Theme_Keyword: Topography
Theme_Keyword: Radar
Theme_Keyword: Interferometric
Theme_Keyword: Remote
Theme_Keyword: Sensing
Theme_Keyword: SAR
Theme_Keyword: DEM
Theme_Keyword: DTM
Theme_Keyword: DSM
Theme_Keyword: ORRI
Theme_Keyword: ORI
Theme_Keyword: STAR-3i
Theme_Keyword: INSAR
Theme_Keyword: IFSAR
Theme_Keyword: IFSARE
Theme_Keyword: GEOSAR
Theme_Keyword: height
Stratum:
Stratum_Keyword_Thesaurus: MEL_Environmental_Domain_Thesaurus
Stratum_Keyword: Terrain
Stratum_Keyword: Earth
Stratum_Keyword: Surface
Stratum_Keyword: Bald
Stratum_Keyword: Ground
Stratum_Keyword: First
Place:
Place_Keyword_Thesaurus: None
Place_Keyword: USA
Place_Keyword: Alaska
Place_Keyword: National
Place_Keyword: Petroleum
Place_Keyword: Reserve
Temporal:
Temporal_Keyword_Thesaurus: None
Temporal_Keyword: 2001
Temporal_Keyword: August
Access_Constraints: Purchase
Use_Constraints: None
Point_of_Contact:
Contact_Information:
Contact_Position: Vice-President E-Business
Contact_Organization_Primary:
Contact_Organization: Intermap Technologies Inc.
Contact_Address:
Address_Type: mailing address
Address: 9785 South Maroon Circle, Suite 150
City: Englewood
State_or_Province: CO
Postal_Code: 80112-5928
Country: USA
Contact_Voice_Telephone: (303) 708-0955
Contact_Facsimile_Telephone: (303) 708-0952
Contact_Electronic_Mail_Address: <mailto:info@globalterrain.com>
Browse_Graphic:
Browse_Graphic_File_Name: <URL:hara2nwmhb.jpg>
Browse_Graphic_File_Description: Thumbnail of DSM in greyscale
Browse_Graphic_File_Type: 8 bit jpeg
Data_Set_Credit:
This data was produced by the Airborne Operations group and the GT Products group at Intermap Technologies Inc.
Native_Data_Set_Environment:
This data is delivered on interoperable media with metadata, thumbnail images and quality control report. The data set was developed on a Sun ULTRA SPARC 2 computer system running Solaris (UNIX).
Data_Quality_Information:
Attribute_Accuracy:
Attribute_Accuracy_Report:
Calculation of the digital elevation model is described in the GT Product Handbook User's Guide. <URL:http://www.globalterrain.com/gt.asp#Product Handbook>
Logical_Consistency_Report: <URL:hara2nwmhb.pdf> contains a final Quality Control report.
Completeness_Report:
Coverage maps are provided for each area of acquisition. <URL:http://www.globalterrain.com/GTCoverage.html>
Positional_Accuracy:
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report:
All data products are 2.5 meters RMSE or better in horizontal accuracy. For details, see <URL:http://www.globalterrain.com/gt.asp#Product Handbook> .
Vertical_Positional_Accuracy:
Vertical_Positional_Accuracy_Report:
GT2 data products are 2 meters RMSE or better in vertical accuracy. For details, see <URL:http://www.globalterrain.com/gt.asp#Product Handbook> .
Lineage:
Process_Step:
Process_Date: 20011220
Process_Description:
This GLOBAL Terrain DEM data product was derived using Intermap Technologies STAR-3i airborne interferometric SAR data acquisition system. The flying height is 19,000 feet Above Mean Ground. The primary look direction is South. Areas of missing data are interpolated using continuous curvature spline over non-data areas. The phase unwrapper utilized is ifprocT. Most incidences of non-data areas are due to radar shadow and layover due to steep terrain. Radar shadow is a factor of the local topography. It is often found in mountainous regions and the urban canyons of built-up areas. Occurances of non-data areas within a DEM are dependent on the look direction of the radar. Significant bodies of water are assigned an elevation which corresponds to the shoreline. Areas of null data are assigned the value -32767.
Spatial_Data_Organization_Information:
Direct_Spatial_Reference_Method: Raster
Raster_Object_Information:
Raster_Object_Type: Grid Cell
Row_Count: 2906
Column_Count: 2440
Spatial_Reference_Information:
Horizontal_Coordinate_System_Definition:
Planar:
Grid_Coordinate_System:
Grid_Coordinate_System_Name: Universal Transverse Mercator
Universal_Transverse_Mercator:
UTM_Zone_Number: 5
Transverse_Mercator:
Scale_Factor_at_Central_Meridian: 0.9996
Longitude_of_Central_Meridian: 153 degrees West
Latitude_of_Projection_Origin: 0
False_Easting: 500000.0 meters
False_Northing: 0.0 meters
Planar_Coordinate_Information:
Planar_Coordinate_Encoding_Method: coordinate pair
Coordinate_Representation:
Abscissa_Resolution: 5.0
Ordinate_Resolution: 5.0
Planar_Distance_Units: Meters
Geodetic_Model:
Horizontal_Datum_Name: NAD83
Ellipsoid_Name: Geoid99
Semi-major_Axis: 6378206.4
Denominator_of_Flattening_Ratio: 294.98
Vertical_Coordinate_System_Definition:
Altitude_System_Definition:
Altitude_Datum_Name: NAVD88
Altitude_Resolution: 0.01 m
Altitude_Distance_Units: meter
Altitude_Encoding_Method: Implicit coordinate
Entity_and_Attribute_Information:
Detailed_Description:
Entity_Type:
Entity_Type_Label: 5 meter posting grid cell
Entity_Type_Definition:
The DEM is a 32 bit IEEE floating point value Big Endian organized in a one-channel binary interleaved file (BIL) on a 7.5-minute by 18.0-minute geographic (lat/long) grid in UTM projection. The origin of the post is center center.
Entity_Type_Definition_Source: <URL:http://www.globalterrain.com/gt.asp#Product Handbook>
Attribute:
Attribute_Label: Elevation value per grid cell.
Attribute_Definition: Height of the geoid, relative to mean sea level.
Attribute_Definition_Source: <URL:http://www.globalterrain.com/gt.asp#Product Handbook>
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 0.800
Range_Domain_Maximum: 38.419
Attribute_Units_of_Measure: meters
Attribute_Measurement_Resolution: 0.01 m
Overview_Description:
Entity_and_Attribute_Overview:
Project Information
Project Area: National Petroleum Reserve Alaska
Intermap Project Number: 01226
Mission # (s): 327
Intermap Processing AML Version: 1.0.7, 20010920
ISO 9001 Certification No.: A8379
DEM Extents
UTM_Easting_(meters): Min. 567645 Max. 579845
UTM_Northing_(meters): Min. 7780695 Max. 7795225
DEM Origin (North West Corner)
UTM_Easting_(meters): North West Pixel 567647.50
UTM_Northing_(meters): North West Pixel 579842.50
Entity_and_Attribute_Detail_Citation:
<URL:http://www.globalterrain.com/gt.asp#Product Handbook>
Metadata_Reference_Information:
Metadata_Date: 20020227
Metadata_Contact:
Contact_Information:
Contact_Position: Vice-President E-Business
Contact_Organization_Primary:
Contact_Organization: Intermap Technologies Inc.
Contact_Address:
Address_Type: mailing address
Address: 9785 South Maroon Circle, Suite 150
City: Englewood
State_or_Province: CO
Postal_Code: 80112-5928
Country: USA
Contact_Voice_Telephone: (303) 708-0955
Contact_Facsimile_Telephone: (303) 708-0952
Contact_Electronic_Mail_Address: <mailto:info@globalterrain.com>
Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata
Metadata_Standard_Version: FGDC-STD-001-1998
Generated by mp version 2.5.6 on Wed Feb 27 15:21:53 2002

Appendix G.  Intermap GLOBAL Terrain: "dsm3v1.bil"

GLOBAL Terrain: "dsm3v1.bil"

Metadata also available as - [ Parseable text ] - [XML ]

Metadata:


Identification_Information:
Citation:
Citation_Information:
Originator: Intermap Technologies Inc.
Publication_Date: 20020124
Title: GLOBAL Terrain: "dsm3v1.bil"
Edition: 1
Geospatial_Data_Presentation_Form: Digital Elevation Model
Series_Information:
Series_Name: GLOBAL Terrain Digital Surface Models
Issue_Identification: Version 1
Publication_Information:
Publication_Place: Englewood, CO
Publisher: Intermap Technologies Inc.
Online_Linkage:<URL:http://www.globalterrain.com>
Online_Linkage:<URL:http://www.intermaptechnologies.com>
Online_Linkage: <URL:http://www.globalterrain.com/gt.asp#Product Handbook>
Description:
Abstract:
This data set is a digital elevation model (DEM) product that populates the GLOBAL Terrain product catalog. The DEM products are generated using the Intermap STAR-3i airborne interferometric synthetic aperture radar (SAR) system mounted in a LearJet 36A aircraft.

The GLOBAL Terrain Digital Surface Model (DSM) data files are digital representations of cartographic information in a grid form. DSMs consist of a sampled array of elevations for a number of ground positions at regularly spaced intervals. These digital data files are produced by Intermap Technologies Inc.(Intermap) as part of the GLOBAL Terrain product line and are licensed in 7.5-minute tiles for areas located between 0 and 56 degrees North/South. Data for locations above 56 degrees North/South are licensed in 15-minute by 7.5-minute tiles.

GLOBAL Terrain DSM products represent the first reflective surface as illuminated by the radar. Accuracy statements are based on areas of moderate terrain. Diminished accuracies are to be expected in areas of extreme terrain and dense vegetation.

GLOBAL Terrain DSMs are produced within four classes of vertical accuracy. GTF DSMs have an accuracy of 0.5m Root Mean Square Error (RMSE) or better. GT1 DSMs have an accuracy of 1.0m RMSE or better. GT2 DSMs have an accuracy of 2.0m RMSE or better. GT3 DSMs have an accuracy of 3.0 RMSE or better. No in-scene ground control points are required for GT2 and GT3 products provided that the DGPS ground station is within 200 km of the data acquisition area. The GTF and GT1 products do require in-scene ground control.

The DSM data for 7.5-minute units correspond to the USGS 1:24,000 and 1:25,000 scale topographic quadrangle map series for available areas in the United States and throughout the world. Each 7.5-minute DSM is based on 5- by 5-meter, or 10- by 10-meter post spacing using the Universal Transverse Mercator (UTM) projection. Each 7.5- by 7.5-minute tile provides full coverage with overlap into adjacent tiles.

Purpose:
The purpose of this data set is to provide a source for current and accurate digital elevation models with vertical accuracy of between 0.5 meter and 3 meters and post spacing of 5 or 10 meters.

The DSMs are used as a fundamental layer of information in Geographic Information Systems (GIS) and Spatial Information Decision Support Systems (DSS). A number of the priority layers of spatial information recognized by the National Spatial Data Infrastructure may be derived from GLOBAL Terrain DEMs, including elevation, hydrography, slope, aspect, and shoreline delineation.

Supplemental_Information:
The STAR-3i system employs three principle technologies: X-band Horizontal -Horizontal (HH) polarized SAR, a ring laser-based inertial measurement unit (IMU), and Differential Global Positioning System (DGPS). STAR-3 i was developed by the Environmental Research Institute of Michigan (ERIM) under contract to the U.S. Defense Advanced Research Projects Agency (DARPA).

The system is comprised of two X-band radar antennae that collect data simultaneously. The set of acquired data are "interfered" by a digital correlation process to extract terrain height data and geometrically correct radar images. STAR-3 i uses post-processed DGPS data, together with precise inertial measurement data, to attain highly accurate positioning control. Precise terrain height and positioning data are enhanced by careful calibration of the baseline separating the two antennae.

The STAR-3i system accuracy has been independently validated by tests conducted by the U.S. Army Topographic Engineering Center, the Institute of Navigation, Stuttgart University and by NASA. A summary of test results are accessible at <URL:http://www.globalterrain.com> .

The GLOBAL Terrain folder name describes the geographic location of a tile. The GLOBAL Terrain file name encapsulates the GT processing level and the product version number. A complete explanation of the GLOBAL Terrain file name can be found in the GLOBAL Terrain Product Handbook. <URL:http://www.globalterrain.com/gt.asp#Product Handbook> .

Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 20010802
Ending_Date: 20010802
Currentness_Reference:
The above dates refer to the time of field data acquisition and therefore reflect ground conditions at that time.
Status:
Progress: Complete
Maintenance_and_Update_Frequency: Ongoing
Spatial_Domain:
Bounding_Coordinates:
West_Bounding_Coordinate: -150.000
East_Bounding_Coordinate: -149.750
North_Bounding_Coordinate: 62.500
South_Bounding_Coordinate: 62.375
Keywords:
Theme:
Theme_Keyword_Thesaurus: MEL_Scientific-Engineering_Field_Thesaurus
Theme_Keyword: Elevation
Theme_Keyword: Cartography
Theme_Keyword: Geodesy
Theme_Keyword: Geography
Theme_Keyword: Hypsography
Theme_Keyword: Mapping
Theme_Keyword: Photogrammetry
Theme_Keyword: Stereophotogrammetry
Theme_Keyword: Topography
Theme_Keyword: Radar
Theme_Keyword: Interferometric
Theme_Keyword: Remote
Theme_Keyword: Sensing
Theme_Keyword: SAR
Theme_Keyword: DEM
Theme_Keyword: DTM
Theme_Keyword: DSM
Theme_Keyword: ORRI
Theme_Keyword: ORI
Theme_Keyword: STAR-3i
Theme_Keyword: INSAR
Theme_Keyword: IFSAR
Theme_Keyword: IFSARE
Theme_Keyword: GEOSAR
Theme_Keyword: height
Stratum:
Stratum_Keyword_Thesaurus: MEL_Environmental_Domain_Thesaurus
Stratum_Keyword: Terrain
Stratum_Keyword: Earth
Stratum_Keyword: Surface
Stratum_Keyword: Bald
Stratum_Keyword: Ground
Stratum_Keyword: First
Place:
Place_Keyword_Thesaurus: None
Place_Keyword: USA
Place_Keyword: Alaska
Place_Keyword: Windy
Place_Keyword: Pass
Temporal:
Temporal_Keyword_Thesaurus: None
Temporal_Keyword: 2001
Temporal_Keyword: August
Access_Constraints: Purchase
Use_Constraints: License Agreement
Point_of_Contact:
Contact_Information:
Contact_Position: Vice-President E-Business
Contact_Organization_Primary:
Contact_Organization: Intermap Technologies Inc.
Contact_Address:
Address_Type: mailing address
Address: 9785 South Maroon Circle, Suite 150
City: Englewood
State_or_Province: CO
Postal_Code: 80112-5928
Country: USA
Contact_Voice_Telephone: (303) 708-0955
Contact_Facsimile_Telephone: (303) 708-0952
Contact_Electronic_Mail_Address: <mailto:info@globalterrain.com>
Browse_Graphic:
Browse_Graphic_File_Name: <URL:dsm3thnv1.jpg>
Browse_Graphic_File_Description: Thumbnail of DSM in greyscale
Browse_Graphic_File_Type: 8 bit jpeg
Data_Set_Credit:
This data was produced by the Airborne Operations group and the GT Products group at Intermap Technologies Inc.
Security_Information:
Security_Classification_System: GLOBAL Terrain End User's License Agreement (GTEULA)
Security_Classification: License Agreement.
Security_Handling_Description:
The user agrees to read and abide by the License Agreement. Copyright Intermap Technologies Inc., 1997-2001. All rights reserved. Refer to the license document on the website. <URL:http://www.globalterrain.com/gt.asp#GT20EULA> .
Native_Data_Set_Environment:
This data is delivered on interoperable media with metadata, thumbnail images and quality control report. The data set was developed on a Sun ULTRA SPARC 2 computer system running Solaris (UNIX).
Cross_Reference:
Citation_Information:
Originator: Intermap Technologies Inc.
Publication_Date: 20020124
Title: GLOBAL Terrain: "orripv1.tif"
Edition: 1
Geospatial_Data_Presentation_Form: Orthorectified Radar Image (ORRI)
Series_Information:
Series_Name: GLOBAL Terrain Orthorectified Radar Images
Issue_Identification: Version 1
Online_Linkage:<URL:http://www.globalterrain.com>
Online_Linkage:<URL:http://www.intermaptechnologies.com>
Online_Linkage: <URL:http://www.globalterrain.com/gt.asp#Product Handbook>
Online_Linkage: <URL:orripthnv1.jpg>
Data_Quality_Information:
Attribute_Accuracy:
Attribute_Accuracy_Report:
Calculation of the digital elevation model is described in the GT Product Handbook User's Guide. <URL:http://www.globalterrain.com/gt.asp#Product Handbook>
Logical_Consistency_Report: <URL:qcv1.pdf> contains a final Quality Control report.
Completeness_Report:
Coverage maps are provided for each area of acquisition. <URL:http://www.globalterrain.com/GTCoverage.html>
Positional_Accuracy:
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report:
All data products are 2.5 meters RMSE or better in horizontal accuracy. For details, see <URL:http://www.globalterrain.com/gt.asp#Product Handbook> .
Vertical_Positional_Accuracy:
Vertical_Positional_Accuracy_Report:
GT3 data products are 3 meters RMSE or better in vertical accuracy. For details, see <URL:http://www.globalterrain.com/gt.asp#Product Handbook> .
Lineage:
Process_Step:
Process_Date: 20020124
Process_Description:
This GLOBAL Terrain DSM data product was derived using Intermap Technologies STAR-3i airborne interferometric SAR data acquisition system. The flying height is 30,000 feet Above Mean Ground. The primary look direction is Northwest. The secondary (alternate) look direction is Northeast. Areas of missing data are interpolated using continuous curvature spline over non-data areas. The phase unwrapper utilized is ifprocT. Most incidences of non-data areas are due to radar shadow and layover due to steep terrain. Radar shadow is a factor of the local topography. It is often found in mountainous regions and the urban canyons of built-up areas. Occurances of non-data areas within a DEM are dependent on the look direction of the radar. Significant bodies of water are assigned an elevation which corresponds to the shoreline. Areas of null data are assigned the value -32767.
Spatial_Data_Organization_Information:
Direct_Spatial_Reference_Method: Raster
Raster_Object_Information:
Raster_Object_Type: Grid Cell
Row_Count: 1494
Column_Count: 1701
Spatial_Reference_Information:
Horizontal_Coordinate_System_Definition:
Planar:
Grid_Coordinate_System:
Grid_Coordinate_System_Name: Universal Transverse Mercator
Universal_Transverse_Mercator:
UTM_Zone_Number: 6
Transverse_Mercator:
Scale_Factor_at_Central_Meridian: 0.9996
Longitude_of_Central_Meridian: 147 degrees West
Latitude_of_Projection_Origin: 0
False_Easting: 500000.0 meters
False_Northing: 0.0 meters
Planar_Coordinate_Information:
Planar_Coordinate_Encoding_Method: coordinate pair
Coordinate_Representation:
Abscissa_Resolution: 10.0
Ordinate_Resolution: 10.0
Planar_Distance_Units: Meters
Geodetic_Model:
Horizontal_Datum_Name: WGS84
Ellipsoid_Name: WGS84
Semi-major_Axis: 6378206.4
Denominator_of_Flattening_Ratio: 294.98
Vertical_Coordinate_System_Definition:
Altitude_System_Definition:
Altitude_Datum_Name: Mean Sea Level (EGM96)
Altitude_Resolution: 0.01 m
Altitude_Distance_Units: meters
Altitude_Encoding_Method: Implicit coordinate
Entity_and_Attribute_Information:
Detailed_Description:
Entity_Type:
Entity_Type_Label: 10.0 meter posting grid cell
Entity_Type_Definition:
The DSM is a 32 bit IEEE floating point value Big Endian organized in a one-channel binary interleaved file (BIL) on a 7.5-minute geographic (lat/long) grid in UTM projection. The origin of the pixel is center center.
Entity_Type_Definition_Source: <URL:http://www.globalterrain.com/gt.asp#Product Handbook>
Attribute:
Attribute_Label: Elevation value per grid cell.
Attribute_Definition: Height of the geoid, relative to mean sea level.
Attribute_Definition_Source: <URL:http://www.globalterrain.com/gt.asp#Product Handbook>
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 294.670
Range_Domain_Maximum: 419.589
Attribute_Units_of_Measure: meters
Attribute_Measurement_Resolution: 0.01 m
Overview_Description:
Entity_and_Attribute_Overview:
Project Information
Project Area: Windy Pass Alaska
Intermap Project Number: 01223f
Mission # (s): 330
Intermap Processing AML Version: 1.0.7, 20010920
ISO 9001 Certification No.: A8379
DEM Origin (Northeast corner)
UTM_Easting_(meters): Min. 343100 Max. 360100
UTM_Northing_(meters): Min. 6918760 Max. 6933690
Entity_and_Attribute_Detail_Citation:
<URL:http://www.globalterrain.com/gt.asp#Product Handbook>
Metadata_Reference_Information:
Metadata_Date: 20020227
Metadata_Contact:
Contact_Information:
Contact_Position: Vice-President E-Business
Contact_Organization_Primary:
Contact_Organization: Intermap Technologies Inc.
Contact_Address:
Address_Type: mailing address
Address: 9785 South Maroon Circle, Suite 150
City: Englewood
State_or_Province: CO
Postal_Code: 80112-5928
Country: USA
Contact_Voice_Telephone: (303) 708-0955
Contact_Facsimile_Telephone: (303) 708-0952
Contact_Electronic_Mail_Address: <mailto:info@globalterrain.com>
Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata
Metadata_Standard_Version: FGDC-STD-001-1998
Generated by mp version 2.5.6 on Wed Feb 27 07:19:25 2002

Appendix H.  TerraPoint Metadata File

Identification_Information:
Citation:
Citation_information:
Originator: TerraPoint LLC
Publication_Date: 2000.01.27
Publication_Time: Unknown
Title: Devils Lake, ND (q47098h33, Pekin NE SW)
Edition: 1
Publication_Information:
Publication_Place: Houston, TX
Publisher: TerraPoint LLC
Description:
Abstract:
The Devils Lake, ND Surface Database consists of x, y, and z point
data derived from an Airborne LIDAR Topographic Mapping System (ALTMS).
The x, y, and z values are stored in ArcInfo Interchange Files.
Purpose:
Data was created so that it could be used as highly accurate, inexpensive
way to create digital topographic vector and raster files for
implementation in Geographic Information Systems (GIS).
Supplemental_Information:
The data points are nominally spaced at 1.3-meter intervals with approximately
a 0.9 meter horizontal accuracy. The 1.3-meter spacing may vary in areas not
reflective to laser pulses, such as water bodies, dark asphalt roofs,
and some types of glass or fiberglass construction.
Surface elevation value accuracy is better than 30 centimeters. Flight altitude
is approximately 915 meters, creating a data swath of approximately 550 meters.
The elevation data provided is for the earth's surface and includes vegetation,
such as trees and shrubs, as well as the built environment.
Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times
Beginning_Date: 1999.12.21
Ending_Date: In progress
Currentness_Reference: "ground condition"
Status:
Progress: in progress
Maintenance_and_Update_Frequency: as needed
Spatial_Domain:
Bounding_Coordinates:
West_Bounding_Coordinate: 546678.436
East_Bounding_Coordinate: 551407.887
North_Bounding_Coordinate: 5309582.191
South_Bounding_Coordinate: 5302599.682
Keywords:
Theme:
Theme_Keyword_Thesaurus: none
Theme_Keyword: topographic
Place:
Place_Keyword_Thesaurus: none
Place_Keyword: Devils Lake, ND
Access_Constraints: none
Use_Constraints:
The Licensee shall not (a) reproduce or copy any or all of the Database
except for back-up, archival purposes; (b) display or permit access to the
Database on the Internet, or any intranet or other electronic network
accessible by more than five users which shall be confined to a single
"site"; (c) sublicense, sell, loan, rent, pledge, assign, share,or otherwise
transfer or assign any or all of the Database; or (d) extract, disassemble,
reverse engineer or modify the Database, or create derivative works
including- digital elevation models; digital terrain models; topographic
maps; contour maps; any type of point or grid representation of elevation
data; or any product or service which recreates, reverse engineers, derives
or approximates, or which can be used as a method or means to recreate,
reverse engineer, derive or approximate, any material portion of the Database.
Point_of_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Dan Phillips
Contact_Organization: TerraPoint LLC
Contact_Position: Director, Data Processing
Contact_Address:
Address_Type: mailing and physical address
Address: 4800 Research Forest Drive
City: The Woodlands
State_or_Province: TX
Postal_Code: 77381-4142
Country: US
Contact_Voice_Telephone: (281) 364-4082
Contact_Facsimile_Telephone: (281) 363-7931
Contact_Electronic_Mail_Address: dan.phillips@transamerica.com
Hours_of_Service: 9-5 CST
Data_Quality_Information:
Positional_Accuracy:
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report:
The data points are nominally spaced at 1.3-meter intervals with
approximately a 0.9 meter horizontal accuracy.
Vertical_Positional_Accuracy:
Vertical_Positional_Accuracy_Report:
Surface elevation value accuracy is better than 30 centimeters.
Spatial_Reference_Information:
Horizontal_Coordinate_System_Definition:
Coordinate_System_Name: Universal Transverse Mercator
Universal_Transverse_Mercator:
UTM_Zone_Number: 14
Transverse_Mercator:
Scale_Factor_at_Central_Meridian: 0.9996
Longitude_of_Central_Meridian: -99.00
Latitude_of_Projection_Origin: 0.0
False_Easting: 0.0
False_Northing: 0.0
Distance_Units: meters
Geodetic_Model:
Horizontal_Datum_Name: North American Datum of 1983
Ellipsoid_Name: GRS80
Semi-major_Axis: 6378137
Denominator_of_Flattening_Ratio: 298.257
Vertical_Coordinate_System_Definition:
Altitude_System_Definition:
Altitude_Datum_Name: National Geodetic Vertical Datum of 1929
Altitude_Resolution: 0.01
Altitude_Distance_Units: Feet
Altitude_Encoding_Method: Explicit elevation coordinate included with
horizontal coordinates
Distribution_Information:
Distributor:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Dan Phillips
Contact_Organization: TerraPoint LLC
Contact_Position: Director, Data Processing
Contact_Address:
Address_Type: mailing and physical address
Address: 4800 Research Forest Drive
City: The Woodlands
State_or_Province: TX
Postal_Code: 77381-4142
Country: US
Contact_Voice_Telephone: (281) 364-4082
Contact_Facsimile_Telephone: (281) 363-7931
Contact_Electronic_Mail_Address: dan.phillips@transamerica.com
Hours_of_Service: 9-5 CST
Standard_Order_Process:
Digital_Form:
Digital_Transfer_Information:
Format_Name: ArcInfo Interchange
Format_Version_Date: 1999-12-21
Format_Specification:
Data are fixed format. Each CD-ROM contains an ArcInfo Interchange file

of an ArcInfo Point Cover, and a metadata file (.met) {i.e. this file },
for the relevant USGS quarter quads. These text files are named using the
same naming convention employed for the USGS quarter quadrangle catalog.
This convention employs a unique 9 character alpha-numeric code preceded
by the letter 'q' which denotes one-fourth of a quadrangle and followed by
a single numeric designation for the quarter-quadrangle:
(1=NW;2=NE;3=SW;4=SE).
Format_Information_Content:
Each point in the cover contains the elevation at that location contained
in the attribute "z".
File_Decompression_Technique: Lempel-Ziv encoding (LZ77), UNIX gzip and
Windows WinZip compatible
Digital_Transfer_Option:
Offline_Option:
Offline_Media: CD-ROM
Recording_Format: ISO 9660
Fees: Various. Contact Dan Phillips. (see Contact Person)
Ordering_Instructions: contact Dan Phillips. (see Contact Person)
Metadata_Reference_information:
Metadata_Date: 2000.01.27
Metadata_Review_Date: 2000.01.27
Metadata_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Dan Phillips
Contact_Organization: TerraPoint LLC
Contact_Position: Director, Data Processing
Contact_Address:
Address_Type: mailing and physical address
Address: 4800 Research Forest Drive
City: The Woodlands
State_or_Province: TX
Postal_Code: 77381-4142
Country: US
Contact_Voice_Telephone: (281) 364-4082
Contact_Facsimile_Telephone: (281) 363-7931
Contact_Electronic_Mail_Address: dan.phillips@transamerica.com
Hours_of_Service: 9-5 CST
Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata
Metadata_Standard_Version: FGDC-STD-001-1998
Appendix I.  Enerquest Metadata File

sb1_3_dempst

Metadata also available as

Metadata:


Identification_Information:
Citation:
Citation_Information:
Originator: EnerQuest Systems, LLC
Publication_Date: August 2001
Title: sb1_3_dempst
Geospatial_Data_Presentation_Form: raster digital data
Online_Linkage:
\\carbon\Z\20039_repair\raw_proc_postflood\sandbars\dems\sb1_3_dempst
Description:
Abstract:
Postflood sandbar DEM surface from a sandbar TIN surface.

DEM covers sandbar 1_3.

Purpose: Cartographic representation of topography
Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: September 15, 2000
Beginning_Time: unknown
Ending_Date: September 18, 2000
Ending_Time: unknown
Currentness_Reference: ground condition
Status:
Progress: Complete
Maintenance_and_Update_Frequency: None planned
Spatial_Domain:
Bounding_Coordinates:
West_Bounding_Coordinate: -111.619030
East_Bounding_Coordinate: -111.601262
North_Bounding_Coordinate: 36.859254
South_Bounding_Coordinate: 36.838012
Keywords:
Theme:
Theme_Keyword_Thesaurus: None
Theme_Keyword: LIDAR
Theme_Keyword: DEM
Theme_Keyword: Topography
Place:
Place_Keyword: Grand Canyon
Place_Keyword: Glen Canyon Dam
Place_Keyword: Colorado River
Place_Keyword: Arizona
Temporal:
Temporal_Keyword: 2000
Temporal_Keyword: August
Access_Constraints: None
Use_Constraints: None
Point_of_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Steve Mietz
Contact_Organization: Grand Canyon Monitoring and Research Center
Contact_Position: GIS Coordinator
Contact_Address:
Address_Type: mailing and physical address
Address: 2255 North Gemini Drive
City: Flagstaff
State_or_Province: Arizona
Postal_Code: 86001
Contact_Voice_Telephone: 520-556-7050
Contact_Facsimile_Telephone: 520-556-7368
Contact_Electronic_Mail_Address: smietz@usgs.gov
Hours_of_Service: 8am-5pm, Mountain Time
Native_Data_Set_Environment:
Microsoft Windows NT Version 4.0 (Build 1381) Service Pack 5; Esri ArcCatalog 8.1.0.642
Data_Quality_Information:
Attribute_Accuracy:
Attribute_Accuracy_Report:
Elevation attribute data information was derived from coordinate information created using LIDAR data collected with a design specification of 15 cm vertical accuracy (RMSE) and nominal 1 meter point spacing.
Quantitative_Attribute_Accuracy_Assessment:
Attribute_Accuracy_Value: 15.4 vertical RMSE
Attribute_Accuracy_Explanation:
Compared to GCMRC GPS survey collected along river camp site locations.
Completeness_Report: All ground and vegetation features exist in the dataset.