Robert. Kletzli and John Peterson, EarthData LLC

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Denise Chavez and Becky Edwards, City of Rio Rancho

Rio Rancho, New Mexico resides just outside of Albuquerque, in Sandoval County. As the home of Intel Corporation and other high tech businesses, it is one of the fastest growing cities in the U.S. Like many cities struggling with the impact of rapid growth, Rio Rancho turned to GIS technology as a planning, infrastructure maintenance and information management tool. To get the best value for their limited funding, and faced with the need for very rapid turnaround, Rio Rancho teamed with a private sector company, EarthData LLC, of Albuquerque, NM, to utilize state of the art photogrammetric techniques for the development of an accurate image base map which will serve as a foundation for their ArcInfo GIS. Using Softcopy Photogrammetry augmented with airborne GPS, for data acquisition, EarthData developed a 1"=200’ color digital orthophoto image base map with accompanying vector data layers (building footprints and edge of roads). This paper will discuss the utilization of state-of-the-art photogrammetric technologies for GIS development.

Advancements in processes surrounding photogrammetry now afford communities, and other users interested in entering the world of GIS, a method to rapidly capture and create a ready to use cadastral level base maps from which can be generated a variety of thematic information. This paper will explain how this process was carried out for one of the fastest growing cities in the U. S.; Rio Rancho, New Mexico.

Rio Rancho, New Mexico resides just outside of Albuquerque, in Sandoval County, Figure 1. In the early 1960’s Rio Rancho Estates began with the purchase of between 55,000 and 60,000 acres of land by AMREP Corporation. AMREP began selling homesites, particularly in the Northeastern United States. The area was originally advertised as a resort community, or "bedroom" community on the outskirts of the City of Albuquerque. By 1966 the 100^th family moved to Rio Rancho Estates. Census figures from 1970 indicate that Rio Rancho Estates’ population was 1,164 persons, Figure 2.

Then, in 1971, AMREP purchased an additional 35,000 acres of land, creating an overall land area larger than the City of Albuquerque.

In 1981 the City of Rio Rancho incorporated with a population of 10,131. The census figures for 1990 are 32,505 residents of the City of Rio Rancho. This means that from 1980 to 1990, the City saw a 226.2% growth rate, the fastest growing city in the state of New Mexico. For the same period, 1980 to 1990, the City of Albuquerque’s growth rate was 15.6%. In May of 1989, American Demographics Magazine named the City of Rio Rancho the fastest growing small city (micropolitan) in the United States. The City of Rio Rancho’s population estimate for 1996 is 46,000 residents within the City limits. With a strong economic base, including such large scale employers as Intel, J.C. Penney, Intuit, and Fulcrum Direct, the phenomenal growth rate of Rio Rancho is anticipated to continue into the next century.

This growth rate has, of course, brought with it many proverbial "growing pains" in meeting the challenges of. the City’s rapidly growing population and large land size. The City limits currently encompass approximately 54 square miles. Additionally, the City has a 5 mile extra-territorial jurisdiction in all directions, hence creating a potential for managing over 160 square miles.

One of the tools the City of Rio Rancho has decided to use to meet many of its needs is Geographic Information Systems (GIS) technology. In 1992, as part of a road expansion project, the City entered into a partnership with local utility providers and helped finance the purchase of a CAD based parcel map. This map had address and legal description data attached. In 1994, the City Development Department’s Planning Division was charged with further developing the City’s GIS. A parcel database was created from the information contained in the parcel map. A zone atlas, city map, and other planning materials have been generated with this information.

It became apparent, however, that the parcel map had significant errors in addition to not being 100% complete. Using ArcView, the parcel map was converted into an ArcView shape file and the process of adding incomplete and newly developed data began. At this point the City of Rio Rancho contracted with Avid Engineering of Albuquerque, New Mexico (prime contractor for development of the city’s master water plan) and EarthData LLC (sub-contractor to Avid) to obtain softcopy generated color digital ortho photos of Rio Rancho. Using the orthorectified photography as the base map, Rio Rancho personnel will adjust the parcel layer to better represent real world boundary delineations. Based on work performed to date, it is anticipated that the accuracy of the City’s data will be dramatically improved. Following that, the City anticipates some very exciting uses for its GIS. Although an enormous task, the process of inputting data is well on its way. Rio Rancho personnel plan to manage the City’s GIS system using workstation ArcInfo, while serving many of the end users via ArcView, distributed throughout departments, for queries and decision support.

Softcopy Photogrammetry refers to the automated realm of processes previously performed via opto-mechanical devices such as stereo plotters, point marking tools, and photo labs with large format copy cameras. Thanks to research and development coming out of the defense community, and more recently, the motion picture industry, raster scanners, work stations, and powerful software have now redefined the science of photogrammetry. This marriage of technologies has brought the power of rapidly generated and highly accurate mapping, to the doorstep of GIS users. When softcopy techniques are integrated with technology such as Airborne Global Positioning Systems (ABGPS), which automate, and drastically reduce, the labor and time intensive tasks of surveying ground control panels, additional time and resource savings are also realized.

In the spring of 1996 EarthData LLC of Albuquerque was selected to provide photogrammetric services to the City of Rio Rancho, New Mexico. With the end objective of this effort to provide Rio Rancho’s GIS personnel with a color ortho-rectified photo base along with select associated vector features, all in a rapid timeframe, EarthData LLC utilized softcopy photogrammetric technologies in conjunction with softcopy vector data capture techniques, to satisfy the project’s requirements. Also as part of the operational approach for establishing ground control Airborne GPS methods were also used for this project. The final products for this project consist of 1.2-ft. pixel resolution color imagery of over 160 square miles, delivered on indexed Compact Disks with associated vector features.

The specific processes used to accomplish this project included, in sequential order: Airborne GPS/Photo acquisition, Photo scanning, Triangulation, Autocorrelation, Editing, Mosaicking,Vector extraction (point, line, and area features), Sheet formatting, (Tiling), and CD production.

Figure 3. presents the flight plan used to conduct the aerial photo capture mission. The Rio Rancho mission required 11 flight lines flown at 6,000 ft. above the ground which resulted in a total of 589 exposures. This equates to 560 stereo models for the entire project area (at the clients request only 350 of these were processed).

By utilizing Airborne GPS for aerial projects the number of survey ground control points is significantly reduced, meaning the field time required by survey personnel is reduced by as much as 85%. For example, to collect photography to meet National Map accuracies standards, the project required, over 350 exposures and would have called for more than 150 control points, if done conventionally. The project team used 22 ground points and achieved equivalent accuracy.

In the case of the Rio Rancho project, field time was reduced from approximately 28 days, if conducted by conventional methods, to 5 days, with the 4^th day being the day for collection of the photography. Therefore in real terms the aerial photography collection was completed 5 days after the notice was given to proceed, a goal unparalleled in our region.

For GIS personnel considering the option of using Airborne GPS it should be pointed out that the development of a survey control network using airborne GPS techniques is ideal for applications such as:

• Production of topographic and orthophoto mapping with less control than would be required using conventional ground control
• Acquisition of control in areas characterized by dense vegetation, rugged terrain or other prohibitive environmental factors
• Acquisition of control on projects such as military installations involving high security and sensitive areas
• Determination of accurate coordinates of airborne sensors such as remote sensing devices, e.g., multi-spectral scanners, radiometers, digital cameras, etc.
• Precise measurement of excavation or fill quantities such as coal piles and landfills.

After acquisition of the color aerial photography, (using metric cameras calibrated by the USGS) diapositives (mylar contact prints) are generated and scanned by a calibrated photogrammetric scanner at resolutions of approximately 20 microns or 1270 pixels per inch. (Digital imagery is referenced by pixels with each pixel having a specific color). These scanners are calibrated to within a few microns and accommodate aerial film or diapositives. Consistency of radiometric values (tone and color) are also highly controlled during this step. The output files produced by scanning are quite large (450-500 megabytes) and require huge raid arrays and rapid tape devices for archiving and transportation of the scanned imagery. It should be pointed out, however, that much of the disk storage requirements used for processing this type of data are transparent to the end user who receives more manageable sized files delivered on indexed Compact Disks, as the end product.

Once the diapositives are scanned aerial triangulation is initiated. This is the process by which each stereo model’s orientation is derived. By conventional means small holes called pugs are drilled or snapped into the diapositives as place markers and measured in stereo on a highly calibrated device (usually either an analytical stereo plotter or stereo comparitor) relative to the diapositive itself. After measuring a series of these diapositives, all measurements including those of ground control targets are input into an adjustment program which calculates final mapping coordinates through a robust least squares algorithm. In the softcopy world no pugs/snaps are drilled and mensuration is computer aided by image matching techniques. In the desert southwest it is possible to almost completely automate this process with the operator being used only to quality check (QC) the matched data. Totally automated aerial triangulation (AT) is being researched in the photogrammetric software community and is not far away. The semi-automated AT process increases throughput while also increasing accuracy. Individual points are matched by an algorithm designed to look at digital patches of imagery, common to both diapositives, thereby eliminating errors caused by operator interpretation or drilling irregularities. It is our experience that this process is about 30% more accurate than its conventional counterpart.

Following the aerial triangulation adjustment, digital stereo models are created; a process akin to manually placing a pair of overlapping diapositives into an analytical plotter and orienting them to be viewed in stereo by optical methods. The objective of this process is to create a digital surface from the stereo models which represents the real world. The Softcopy method uses a batch program without operator intervention. AC is the process by which the computer matches patches of imagery on each side of the stereo pair and if it determines the imagery to be similar enough it calculates the positions of the patches and goes through the photogrammetric equations (collinearity) to calculate a 3 dimensional coordinate. This process is done 10’s of thousands of times for each stereo pair with the result being a grid of mass points throughout the model. Mass points are the calculated heights of the objects that the pixel patches represent; be they dirt, concrete, bush, tree or building. If the particular item is not on the ground (having all of your points on the ground is what you’re striving for to create a surface), i.e., a tree or building, that data point must be edited by a stereo capable operator to "push" the point down to the ground.

Color digital orthophotos are becoming a more common foundation by which GIS databases are built. By conventional means, digital orthophotography is an expensive add-on product due to the requirements of scanning, orientation and ground surface formatting. In the Softcopy world, all of these setup issues have already been performed by the time the surfaces have been completed, hence, only the rectification process is an additional step. As a result, the additional cost to produce digital orthophotos, in a Softcopy environment, is significantly less than adding them to a conventional photogrammetric workflow. Figure 4. represents an example of a final color digital ortho-photo.

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After orthorectification, has been completed, it is a necessary QC step to visually edgematch all adjacent orthophotos to each other. We use an Avenue Script, we have written, to view the files in ArcView to mark any suspect areas with a circumscribed polygon that is written out as an ASCII file. This is used in our surface generation module for reference.

Using the hardware born out of Hollywood, as previously mentioned, we are able to digitally mosaic hundreds of digital orthophotos at a time. Radiometric (tone&color) corrections are performed by image histogram analysis and applied across the entire mosaic. Because the mosaic is digital it is also possible to resample it to any pixel size for display at various scales and as a backdrop to any GIS data.

Most GIS databases include vector information, typically roads, buildings, parcels and drainage features. Such is the case with Rio Rancho. EarthData was contracted to acquire edge of roads, buildings and contours. By conventional photogrammetric methods vectors are captured in an analytical plotter by what is essentially a 3D etch-a-sketch method. The features are traced in the instrument by following each feature and are displayed on a graphics workstation in close proximity to the instrument itself. The operators visually compare the color vectors in the graphics monitor with the features they see in the plotter instruction; a process requiring duel physical attention between two devices. In Softcopy, the vectors, including the contours are superimposed in color and 3D, on top of the stereo image, all on the workstation’s screen. Therefore as soon as the operator digitizes a feature it immediately appears on the imagery in front of them. This workflow aids in the QC process because no operator interpretation is required and all vectors are dynamically updated when changes are made. Standard off the shelf CAD packages are used to collect and manipulate the vector information, as has been done for many years. Figure 5. is an example of a final Softcopy generated vector product.

Once all vector information is collected, edgematched and has been through QC/QA procedures, it is time to convert all data to coverages for GIS use. Arc/Cad is used to create topologically structured GIS data. Build is run to create the initial datasets and clean is run to flag dangles, overshoots and unclosed polygons. The Arc/Cad tools are used to adjust the vectors and new coverages are created. Attributes inherent in the data, i.e., elevation, layer, color and any CAD attributes are placed into ARC attribute tables. With the addition of a raster viewing package the color digital orthos may be displayed as a backdrop during the conversion process for additional reference. When all data has been made topologically correct, export files (.e00) are created and written to CDROM for delivery for use with ArcInfo or ArcView on the platform of choice.

As mentioned above, final products are delivered on CDs. In this step the mosaic is tiled into indexed files of managable size. Delivery format for the digital raster products is typically 5,000 x 5,000 pixels, per tile (75 megabyte files) and 8 tiles per CD. All vector data accompanies each respective raster files. We find that this is a managable size and format for quick display when using desktop GIS systems such as ArcView 3.0.

Color hardcopy output from a conventional photo lab is very costly and dependent on the limitations of equipment for producing mapped products at desired output scales. This requires much planning due to the costs involved with alterations. Digital data, on the other hand is scale independent, limited only by original photo scale.

With the advancements in plotter designs, it is now possible to easily produce near photographic quality color plots from the desktop. This approach costs a fraction of the photo lab methods. We have found ArcView 3.0 to be very robust for handling the large plot files associated with orthophotography. This output has been extremely well received in our market.

Rio Rancho GIS personnel feel there will be many beneficiaries from Rio Rancho’s GIS. These include, but are not limited to, Neighborhood Associations, the City Department of Public Safety, the City Utility Department, the City Public Works Department, and the City Development Department. Some of the additional beneficiaries will be Sandoval County, the local dry utilities, Southern Sandoval County Flood Control Authority, the Middle Rio Grande Council of Governments, Rio Rancho Public Schools. Several potential projects among the agencies mentioned have been identified. These include:

Neighborhood Associations

• Neighborhood watch planning
• Reference for public meetings
• Task force use

Department of Public Safety

• Criminal statistics data
• Bicycle patrol areas
• Patrol areas
• Emergency response times and zones
• 911 dispatching

Utility Department

• Facility tracking: pipe locations, PRV maintenance, etc.
• Water system modeling
• Well head protection

Public Works Department

• Flood plain boundaries and planning
• Storm drainage system tracking
• Street centerline / right-of-way; condition inventory
• Easement tracking
• Topographic contours

Development / Planning Department

• Public transportation planning / routing
• Land use data
• Addresses / legal descriptions
• Annexation boundaries
• Septic tank / private well site density
• Traffic volume data
• Zoning
• Construction permit tracking

The potential uses, along with time and money savings, are limited only by how much information the City can continue to merge into its new parcel and aerial generated maps.

Although relatively new, the Softcopy Photogrammetric and associated technologies discussed here, are proven and repeatable for GIS base mapping. As the demand for accurate GIS data continues to rise, digital orthophotography provides a cost-effective, and flexible foundation to construct a GIS database with increased speed and efficiency. This approach gives users of Softcopy derived data the ability to more rapidly launch into project solutions and spinoff applications; upping productivity. The bottom line: Softcopy Photogrammetry is a perfect approach for quick starting a GIS.

The authors would like to thank the following people for their support and interest in this project: Mr. Art Corsie, Director, Rio Rancho, City Development Department and Mr. Larry Webb, Rio Rancho, Director of Utilities.

For more information contact:

Robert Kletzli at 505-872-0207, kletzli@earthdat.com or

John Peterson at 505-872-0207, jpeterso@earthdat.com or

Denise Chavez at 505-896-8782

Becky Edwards at 505-896-87