Using GIS to Access National Ocean Service's Digital Data Products

Dr. Peter L. Grose
Heidi L. Johnson
Nipa Parikh
W. Russell Perry
National Oceanic & Atmospheric Administration
National Ocean Service
Office of Ocean Resources Conservation and Assessment
Strategic Environmental Assessment Division
1305 East-West Hwy., 9th Fl.
Silver Spring, MD 20910-3281

ABSTRACT

National Ocean Service (NOS) within the National Oceanic and Atmospheric Administration (NOAA) is one of the three primary federal mapping agencies and has the responsibility for mapping the coastal zone. Historically, access to primary NOS product has been in traditional forms to traditional users (subject matter specialists) from separate sources. These products include: Aerial Photography from NOS Coastal Surveys, raster images of Topographic Sheets from Coastal Surveys, outlines of Smooth Sheets and availability of digital soundings from Hydrographic Surveys, Nautical Charts, Environmental Sensitivity Index Maps, datasheets for Geodetic Control Points, and locations of Tide Gauges and Water Level Measurements. There is an increasing need to provide NOS products to non-subject matter specialists such as the coastal resource management community, state and local governments, and the general public. These important and growing user groups have difficulty in locating and accessing NOS data because access services are fragmented and products are not in an immediately usable form.

The Office of Ocean Resources Conservation and Assessment, within NOS, has developed both a platform independent stand-alone application and a World Wide Web site to provide one-stop digital access to NOS product data. NOS MapFinder (http://mapindex.nos.noaa.gov) provides the user with an operational service for locating, understanding, determining availability, previewing, and accessing a wide variety of NOS generated digital data. This service is designed to locate and deliver products which can be used immediately rather than data which must be subsequently processed by the user.


INTRODUCTION

For nearly two centuries, the National Ocean Service (NOS) and its predecessors have toiled "on the beaches and in the boats" mapping and describing the physical state of U.S. coastal lands and waters. Traditional products, such as nautical charts and tide tables, have been directed toward ensuring the safe and efficient flow of maritime commerce to and from our Nation's ports. With the advent of the Internet information age, NOS is now targeting many of its products toward more widespread public availability and uses. Direct access and immediate utility are the cornerstones of a new NOS Internet service, the "NOS MapFinder," to be inaugurated in the summer of 1997. A Preview Demonstration of this service was opened for public viewing in March.Work is proceeding on seven initial themes for MapFinder's inaugural launch: coastal photography, coastal survey maps, nautical charts, environmental sensitivity index (ESI) maps, hydrographic surveys, water-level measurement stations, and geodetic control points. Additional themes are planned for future updates.

OUR VISION

The NOS MapFinder is a major outreach effort. Its objective is to deliver maps, aerial photographs, and other spatial information to public and private-sector coastal resource managers, to assist their planning and management activities.

This "one-stop" service will offer immediate access to a variety of NOS products on a single World Wide Web site with a map-based interface. This interface will allow users to locate a local or regional area of interest; find out what information/theme offerings are available for that location; and immediately download specific products. Additionally, the service will provide background and explanatory information for each theme so that users can better understand the source, methods, quality, and limitations of the cogent products.

PREVIEW DEMONSTRATION

Discussions with NOAA colleagues and potential users both within and outside of NOAA, demonstrated considerable interest in this service. This interest prompted the project team and the NOS partners to accelerate work so that a Preview Demonstration of the service could be made available five months before the August inauguration. This preview includes a robust mapping interface with search, zoom, and theme selection capabilities, actual spatial index data and many immediately retrievable products or product examples for all seven themes, and brief descriptive material. The Preview Demonstration can be accessed at: http://mapindex.nos.noaa.gov

DATA & PRODUCT OFFERINGS

The NOS MapFinder is comprised of three elements for each of the seven themes: 1) Overview Material (abstract, two-page description, annotated example of a product, and metadata file in Federal Geographic Data Committee format); 2) a spatial index that locates and describes the comprehensive list of all data collected by NOS for the theme; and 3) digital products and product previews that can be downloaded for direct use.

The spatial indices are comprehensive; that is, they contain all items in the NOS archives. Initially, only a subset of these will be available in digital form, but the subset will grow substantially in coming years. Other digital data sets (some very large) can be ordered on-line for separate delivery. Additionally, printed products can be acquired for the cost of reproduction from the NOS archives.

AERIAL PHOTOGRAPHY

http://mapindex.nos.noaa.gov/MapFinderHTML/IMAGE1.gifSince about 1940, precision aerial photography has been used as source material for coastal survey maps. The NOS photographic library now contains in excess of 500,000 film images. The spatial index for this theme shows the region covered by each photo mission and the footprint of each image. A few thousand scanned photo images (100 dpi) will be initially available. These are the most recent photographs with wide geographic distribution. The project will add 30,000 images in the next two years.

COASTAL SURVEY MAPS

In 1807, President Thomas Jefferson created The Survey of the Coast to chart the U.S. coast and its harbors. One of the products of this still-evolving survey are topographic maps (commonly referred to as T-sheets) that delineate the shoreline and identify other features, such as rocks and tidal flats, that are important for marine navigation and commerce. These maps are a prime source of spatial data in coastal regions, and are often used in legal proceedings. Typically, they cover a coastal region of about 40 square miles. 1,500 (of the 15,000 current and historical maps) have been scanned and will be directly available from MapFinder in the first year. These maps provide complete coverage for the U.S. East and Gulf Coasts.

NAUTICAL CHARTS

The nautical chart is the most fundamental of navigational tools required for safe passage of waterborne commerce. These maps show the location of the shoreline, minimum water depths, aids to navigation, hazards to navigation and much more. Official digital copies are commercially available from BSB Electronic Charts, NOS' business partner. MapFinder provides an on-line Nautical Chart index, with their title, geographic extent, reference number and scale. Preview images of selected charts will be offered for direct download.

ENVIRONMENTAL SENSITIVITY INDEX (ESI) MAPS

ESI maps are an integral component of oil spill contingency planning, and serve as the first source of information in the event of an incident. They contain three general types of information: Shoreline classification (with regard to sensitivity to oil fouling), human-use resources, and biological resources, This plotted on USGS 7.5-minute quadrangle maps. The spatial index identifies all ESI maps. Initially, MapFinder will provide captured images (75 dpi) of about 132 ESI maps for California; the list will grow with subsequent updates.

HYDROGRAPHIC SURVEYS

Hydrographic surveys, the earliest of which date to 1837, determine the configuration of the bottoms and tidal depths of water bodies. Modern surveys include the detection, location, and identification of wrecks and obstructions, primarily through the use of sidescan sonar and multibeam sonar technology. The primary product of a hydrographic survey is a map called a Smooth Sheet, on which is plotted relevant shorelines (from coastal surveys) and water depths corrected to an appropriate tidal datum (usually mean low water). The NOS MapFinder service contains an index of 10,400 surveys. Digital data (point soundings collected since 1930) are stored in a massive archive available from NOS on CD-ROM.

WATER-LEVEL STATIONS

Water-level data are gathered to provide accurate predictions of tide stages. The data are collected at about 130 stations located around the U.S. coast and in the Great Lakes. For this theme, a detailed data sheet, containing descriptions of the specific locations and instrumentation for each station, will be offered.

GEODETIC CONTROL POINTS

The geodetic network provides data required for absolute horizontal and vertical positioning, which creates consistency among individual spatial surveys and maps. It has been established, and is maintained as, a high-accuracy, four-dimensional network of monumented stations at 1° x 1° (75 km to 125 km) nominal spacing throughout the U.S. and its territories. MapFinder locates the most important of these points (~1300), the Federal Base Network and the continuously Operating Reference Stations, and offers a data sheet for each describing its specific location and precision reference data.


DATA INTEGRATION

The MapFinder project is a partnership among eight NOS divisions including the Strategic Environmental Assessment Division, Hazardous Materials Response and Assessment Division, U.S. Coast Survey Development Laboratory, Hydrographic Surveys Division, Ocean and Lake Levels Division, Geodetic Services Division, Photogrammetry Division, and the National Geodetic Survey Systems Development Division. Each division is responsible for providing the data integration team with a spatial index and digital product for their respective theme. Depending on the nature of the theme, the data spans decades of time, various resolution scales, and diverse geographic boundaries. To bring all of the data into a consistent format, the data integration team performed multiple conversions, formatting, and manipulations for incorporation into the MapFinder project.

SPATIAL INDEXES

Spatial indexes for the seven themes were acquired in various formats ranging from DBF and TXT flat files to MapInfo MIF coverages. Customized AVENUE scripts were written to interpret, convert, and create either point or polygon shapefiles from each index. For example, a typical aerial photograph record included a photo center, an azimuth, and a scale. An AVENUE script was written to create a polygon of the photograph footprint and then the footprint was rotated based upon the azimuth. The resulting polygonal theme represented the true footprint of the photographs. The addition of the point themes was straightforward as they could be converted directly into shapefiles based on given latitutle and longitude. Since MapObjects directly handles shapefiles, the indexes were then moved to the MapObjects/IMS server.

DIGITAL PRODUCTS

Digital products for the seven themes were provided in either TXT format (for textual products) or in gif format (for image products). The gif images were purposely degraded from original resolution to 100 dpi to facilitate quick Internet access. By the end of the summer, the ability to order images of higher resolution from the source NOS division will be in place.

When aerial photography is flown, aerial photographs are taken to produce 50% overlap along a flight line. Since there is high cost in producing digital aerial photograph products, the MapFinder service will only provide digital product for every other photograph on a flight line. Users who are interested in obtaining photographs not provided can contact the appropriate NOS division.

SYSTEM ARCHITECTURE

The MapFinder project is located on a Windows NT 4.0 platform and is served through Microsoft's Internet Information Server (IIS). The mapping application is developed with Microsoft's Visual Basic 4.0 and Esri's mapping component software, MapObjects. MapObjects components are a compilation of key mapping functions pulled from a larger GIS desktop application. Esri's Internet Map Server (IMS) is a web server extension that connects the MapObjects application and the IIS to make dynamic maps available over the Internet. Currently, the MapFinder project is accessible on a HTML client with future plans for a Java client. The primary speed enhancing factors of this configuration are discussed below.

WINDOWS NT DESIGN

MapObjects was designed specifically for the Windows NT platform. It utilizes a common code base without having to use third party software to communicate with a variety of platforms. Normal multi-platform applications such as ArcView and ArcInfo would require third party software to enable platform specific operations such as video support and file management.

COMPONENT SOFTWARE

Visual Basic provides access to the individual components in MapObjects for map creation, control, and manipulations. Instead of launching a full-blown desktop application, this component technology allows the developer to build a lean application that incorporates only the necessary functions. Ultimately, this streamlining results in extremely optimized applications that perform efficiently and with speed.

SEPARATE COMPILATION OF HTML PAGE AND IMAGE MAP

The MapObjects/IMS connection quickly and efficiently transfers textual, graphical, and mapping information to the client site by utilizing a two pass approach. Once the user initiates a mapping function, the URL request is passed through the IIS to the IMS. The IMS then sends the request to the MapObjects application which begins to compose the response. First, MapObjects composes the HTML page. As the HTML page is being shipped and drawn on the client's site, the server uses MapObjects to generate an image in the background from the data layers on the project map. By the time the HTML page is arranged on the client's site, the map is ready to be included in its appropriate spot. Consequently, the client will see very little lag time between an action request and an update.

FUNCTIONALITY

NOS MapFinder provides the user with an operational service for locating, understanding, determining availability, previewing, and accessing a wide variety of NOS generated digital data. To access the NOS MapFinder search engine, the user begins at the entry screen where they are asked to select a region of interest from maps of the U.S., Alaska, and Hawaii. Next, the selected area of interest becomes the extents of the new mapping screen. Several tools are available to manipulate the map extents, select or deselect visibility of product themes, and to further refine the product selection. After the data is refined, a search can be initiated to "drill" through the data layers at a particular point with a given radius and return a listing of relevant features.

A continuing challenge with such a wide range of data is providing the user with tools capable of intelligently subsetting and displaying the data in readable format. It is not uncommon for themes to overlap each other and specifically for the themes with wide temporal ranges, to overlap themselves. Three search tools were integrated into the system to help subset the themes. The first two tools are search criteria based on a scale resolution range and a temporal range. If a particular theme does not have a year or scale associated with it then the search will not affect that theme. The third tool is the ability to select only data that has an actual digital product associated with it and is available for download.

Once the themes are appropriately subsetted through the above mentionned search tools, the user can initiate a "Find" command with a selected search radius. The system will search all visible themes and provide the user with a summary listing of all features found within the given search radius for each theme. The final column in the summary listing is the digital product link. When chosen a separate browser window will be launched with the image. If no digital product is available then the user will see an example digital product.

Additionally, access to abstracts, descriptions, and annotated examples of the seven themes and their data offerings is offered through the accompanying surround material. Standard map control functionalities were also integrated to allow the use to pan, zoom in, zoom out, and redraw the map display.

FUTURE CHALLENGES

GEOTIFF PRODUCT

An increased interest in obtaining geo-referenced images for use in desktop GIS applications will move the digital product emphasis to a GEOTIFF product. The gif image would still be used for the user to view in a browser, but the GEOTIFF image would be an alternative digital product available for download. GEOTIFF images can be directly imported into several desktop GIS applications as a base thematic layer.

DYNAMIC RE-PROJECTION OF SHAPEFILES

To aid in the visual presentation of the U.S. shoreline, shapefiles are being re-projected from standard geographic coordinates to a equidistant cylindrical projection. This re-projection must be done in either ArcView or ArcInfo before incorporation into the MapFinder project and permanently affects the shapefiles. A further investigation is needed to pursue the ability to dynamically re-project coordinates on the fly. This would eliminate the need for shapefile re-projection and increase system flexibility.

DIGITAL PRODUCT MARKET BASKET

An important component to the MapFinder service is the ability to deliver products to the user via the World Wide Web. The digital products are now available for download, but only one at a time. A later release (Sept-Oct) of MapFinder will include a service to "collect" digital products in a user's "market basket", bundle them into a file at the end of a user's visit, and make the file available at a FTP site for download. This will save considerable user time that would otherwise be spent viewing each product and performing a manual download.

DISTRIBUTED DATA NETWORK

To minimize the maintenance efforts of the service, it is the intention in subsequent years to distribute the data holdings (indexes and products) back to their source NOS division. The data holdings currently reside on the same Windows NT platform as the Internet Information Server, Internet Map Server, Visual Basic, and MapObjects. As digital products (TIF/GEOTIFF/TXT) are added to the service, data storage will become a concern. Finally, this will allow each NOS division the ability to maintain their own data holdings, perform QA/QC, and administer data updates as they become available.

JAVA CLIENT

A final desired enhancement on the user side is to employ a Java client instead of HTML. A HTML client was chosen to minimize the initial learning curve in designing and implementing the project. A java client would enable rubber banding selections, automatic map redraws, active map controls, instant visibility control of thematic layers, and overall ease of use.

INFORMATION

For more Information, contact:

Dr. Peter L. Grose
NOAA/NOS/SEA Division
1305 East-West Hwy., 9th Fl.
Silver Spring, MD 20910-3281
Ph: 301/713-3000 x132
Fax: 301/713-4384
email: pgrose@seamail.nos.noaa.gov