| "Instant GIS—A Tale of Two Counties
Two counties in Washington implemented full coverage GIS for geo-spatial display.
By Robert F. Obear Introduction
This has been characterized as "The Information Age," and more recently as "The Digital Age," for very good reasons. As the volume of information or digital data generated continues to burgeon, businesses and governments are searching for innovative ways to access, deliver, and manage that information. Working with information involves two distinct spheres of activity; there is the analytical, detailed, and demanding process of creating it; and there is the process of using it, which we want to be intuitive-virtually automatic-and easy. This is particularly true for GIS implementations in county assessor offices that need to be accessed county-wide and shared with the public.
More county offices are discovering a new way to make their GIS plans a reality today, rather than at some distant point in the future. No matter what level of GIS they are currently at-planning, just starting or partially implemented-an 'Instant GIS Program' is possible, as experienced by Cowlitz County and Island County, in Washington state. Using existing maps from various sources, including aged, hand-drawn maps, and then upgrading as new more accurate CAD maps are created, the counties were able to deploy useful GIS information in a matter of weeks. Both counties had the same mandatory objectives:
¥ Minimal installation/start-up time and expense;
¥ Usability by, and accessibility to, all county personnel
—especially those with minimal computer skills;
¥ Compatibility with any county PC workstation, including the assessor's Public-Service Desk;
¥ Quick access to images of county assessor's maps;
¥ Safeguarding originals from damage, wear-and-tear, alteration, or loss;
¥ Maximum ability to link additional information to county assessor's maps;
¥ Rapid, scalable, low-cost copy delivery. Getting Started
The first problem to be attacked is usually the most persistent one, as was apparent with the assessor's offices and their difficulty with providing parcel maps to county personnel and residents in an efficient and timely manner.
Cowlitz County has accumulated over 2,000 maps during its life and history.Island County has more than 2,000 quarter-section maps and close to 50,000 parcels on record in the assessor's data files. The solution in each case was to scan all the county maps and then use SourceViewª, a relational image integration and access system from Momentum Systems Ltd., to locate and display the images to both public and county users. Cowlitz County was first to start implementation. It decided to use a base map of the county that was previously vectorized for its ArcInfo GIS, to serve as a "launchsite." From here, a user could identify an area of interest and then zoom (or "drill-down") to parcel information, so as to be able to print the resulting view, preferably to scale. Accordingly, more than 2,500 maps were scanned and identified either by section, roll map number, addition name, DLC, or other criteria. Next, distinctive color-coded pointers, called "hotspots," were placed on the base-map image to link each detail map to its location on the base map. Map indexes were generated to provide alphanumeric lookup capability.
Island County did basically the same thing, except that it obtained its base map from the Washington State Department of Natural Resources (DNR).
All of the maps in each county were scanned. In each case, part of the work was farmed-out to a vendor who is equipped to process large-format maps and who could easily do one or two thousand scans in a few days. Island County did a lot of its own scanning because it did not require further processing of the scanned maps; Cowlitz County contracted with a provider to supply vector conversions of the scanned maps that could be used to assist in converting its maps into ArcInfo vector maps. Geo-referencing
Island County made immediate use of a new capability in the relational image application, making it possible to register the scanned maps into the North Zone Washington Coordinate System. They used the DNR base map to reference each quarter-section map and then tied the whole mapping system together by registering the base and detail maps into the State Plane Coordinate System. They could now relate all of their detail maps to the base map, which meant that the relationship between detail maps and the base map was defined by X/Y registration and that the assessor's database could be tied to any map in the geo-coordinated system.
Now, for instance, Island County users, even computer novices, could zoom or "drill-down" to the detail-map level using any standard PC. This "zoom" feature allows the user to click on a point of any geo-referenced map image to produce a list of qualifying images of maps that contain the X/Y coordinate of that point. Once displayed, the list can be used to select the image of choice and jump directly to that selection. For example, if the X/Y point is coincidental on a section map, an aquifer map, a wetland map, and a soil slope map, the user can choose which map image from the list to display. Geo-spatial Data Display
Map access by geo-referencing paved the way for true geo-spatial display of county information for both counties. Island County was first to open its assessor's database and create three new fields: X Coordinate, Y Coordinate, and Size. In order to populate these new fields, each of the 50,000 parcels was defined by its X/Y coordinate within the State Plane System.
Another capability of the SourceView relational image software produces a Dialog Box that contains every parcel field on the quarter-section raster map that was currently being displayed. It listed the Parcel ID numbers, from which the user could rapidly drag, click, and measure each of the 50,000 parcels; two users required only five weeks to do this registration. The result was that particulars for any of the 50,000 parcels could be accessed from the base map (or any other registered map)-by reference to zone, hotspot color, or area, for instance. Other Island County departments quickly exploited this GIS function because of its ease of use. Fast and Efficient Color Map Display
Cowlitz County found that the scanned images of its aging manual maps appeared crisp and printed exceptionally well. The SourceView software stores digital images as a Group 4 raster file (TIFF) which is bi-level (each pixel is black or white) and highly compressed. JPEG and BMP color overlays enhance the ability to define with color.
Color maps, exported from any CAD source, retain the full richness of 24-bit color TIFF but afford the efficiency of bi-level TIFF. This means that virtually all of the CAD-based GIS information display can occur on any Windows desktop with fast, efficient, simple, and full-featured geo-spatial data display. The files for these color maps are a fraction of the size of other color files and, as large-format images, may be registered into the State Plane Coordinate System just like other map images. Zooming is normal and the images support hotspots and contrasting overlays. Raster/Vector/Raster Coexistence
The accompanying chart illustrates the present Cowlitz County GIS implementation. Even though the ArcInfo portion is around 50 percent, all of the county mapping is now accessible for GIS display, using either a converted ArcInfo Gp4 raster image or a scanned (best available) Gp4 raster image. What Else and What is Next?
As the Cowlitz County vector implementation proceeds over the next few years, the ratio of vector converted maps to scanned maps will increase, thus improving the accuracy of the system being made available to county administration. In the meantime, however, the maps that have served the county since inception will continue to provide the needed information. Even upon completion of the enterprise GIS, the county has a need to continue provision of a basic level of GIS functionality for county departments by remote access through the network and over the Internet. As stated by Chris Schaefer, GIS manager for Cowlitz County, "[The county] wants this approach to be a key to disseminate data quickly and easily and at low cost as part of the effort to conform to the open records law. Additionally, the GIS department plans to distribute this data to its partners for their own civil engineering and planning applications."
Cowlitz County and Island County, among many others such as the city of Issaquah, Wash., the Port of Tacoma, and the Army Corps of Engineers, offer the ability to selectively view images of maps, drawings, and other documents on the Internet. This eliminates the need to download the large number of files that would be required to examine, for instance, a couple-of-hundred bid and proposal drawings such as for a new dormitory at Edwards Air Force Base in California. By downloading the SVReader component of SourceView over the Internet, a would-be contractor can look at the drawings that relate to his business and plot them to a full-size, high-resolution paper output. Realtors, title companies, and the general public soon will have untrammeled access to maps and data within cities and counties that elect to place their mapping systems on the Internet. Full size maps are loaded quickly because they are relatively small in the Group 4 file format. Panning, zooming, and printing are handled by the local computer rather than the application server. This simplified approach eliminates significant cost and does not require a full vector implementation as a prerequisite. Island County also plans to provide maps and land title data on CD-ROM on a cost recovery basis. Conclusion
Perhaps most important of all is the ability to deploy comprehensive geo-spatial data now. Cowlitz County and Island County typify counties with about 50,000 parcels each. For counties like these, it is now possible to produce 100 percent registered map coverage and to link existing database information to those maps in a brief time. Even large counties and cities have the means to effect full GIS coverage in a fraction of a year. The resulting raster-based 'Instant' GIS enables county offices to cope with the mounting demands of land management, resource development, and environmental planning. Information is readily available, while vector-based development continues for enterprise GIS implementations. In many cases, it will serve as a stand-alone GIS for those who want geo-spatial information and are less concerned with complex system analysis. About the Author:
Robert F. Obear is general manager, SourceView product for Momentum Systems Ltd. in Mukilteo, Wash. He is a mechanical engineer and president of Dataware Electronics Inc., the development company for the SourceView software. He may be reached at e-mail: [email protected] Back |
