The city of Thornton, Colo. has a recipe for achieving tremendous benefits from GIS, without having a line-item GIS budget. The magic ingredient in the recipe is Thornton's finding and buying existing information. The spice is finding existing aerial photography and converting it to digital imagery for a fraction of the cost of digital orthophotos.
      Increased economic development, better planning, reduced labor costs, and improved public safety - all without a line item for GIS may seem like alchemy, but this fast growing suburb of 65,000 has pioneered a technique that can be copied by others.
      Thornton is a Denver, Colo. suburb known for strength in water management: making sure they had enough for growth. This has proven to be important. Thornton is the fastest growing municipality in the Denver area.
      In 1992, Colorado passed Amendment 1, the Tax Limitation Bill. Across the state, city and county governments had to find ways to provide better government while cutting all budgets.
      Thornton's recipe for GIS leadership in this environment starts with, "Getting it in and showing a quick turnaround," according to Audrey Maydew, programmer analyst who is acting as the GIS coordinator. The recipe includes a liberal amount of GIS championing, mixed with central GIS data storage and administration. Added to this is requiring each city department to: participate in the direction of the GIS, have their own knowledge on how to use GIS, and be responsible for maintaining their own data layers.

Beginnings
In 1991, Thornton was like most other cities. Maps were handdrawn. Presentations involved xeroxing, splicing, protractors, and hand typed labels. One typical division, Planning, worked overtime to prepare presentation materials using these archiac methods.
      Thornton's beginnings in both GIS and aerial imagery were fairly innocuous. The community development director had read about GIS, became intrigued, then enthusiastic about the possible benefits. He was the first GIS champion. In May 1992, he convinced the other department heads to provide personnel for the "Better Government Through GIS Commission."
      Subsequent championing of GIS throughout the city have included the MIS director and the finance director. The finance director makes the perfect champion in his ability to find funds, and find multiple benefits from the same expenditures.
      In fact it was the finance director who first suggested the addition of aerial imagery. As users started requesting information with a visual content, he suggested using a scanner designed for text documents and Optical Character Recognition, to scan a photo at 300dpi. The image immediately broke-up when zooming was attempted, but the seeds of the idea had been planted.

Hardware and Software
The original purchase of hardware, software, data, and training was based on a plan developed by the committee that would eventually benefit 14 different city departments. The original hardware and software was a Data General AViiON 4625 with 64MB of RAM, and 3GB of disk space; two X-terminals; a three seat Environmental Systems Research Institute (ESRI) ARC/INFO 6.1.2 license; and an HP Draftmaster II pen plotter. The pen plotter allowed Thornton to show quick turnaround. As GIS output became available from the plotter, interest increased. Department heads started to observe "that GIS was producing better maps more quickly and easily than ever before," remembers Maydew.
      In April of this year, the output of the new HP650C electronic plotter led to increased attention. Which in turn led to a reassessment of the original cost justification. The reassessment was conducted by the "GIS Steering Committee," made up of a representatives of each department. As more GIS layers and applications are developed, the number of anticipated areas of saving has increased significantly- resulting in a greater need for speed and flexibility of the system.
      Based on two current applications and six planned future applications, the Police Department included additional capacity for the entire GIS system in their procurement of a public safety system. The police procured an HP9000 with 256MB of RAM and 8 GB of storage. Storage is very important: Thornton's digital aerial imagery occupies 2GBs, and the new imagery covering Thornton's growth will be even larger.
      Thornton will be adding three additional ARC/INFO seats per year for the next several years. Thornton's target for software licenses is 24 simultaneous users. At the suggestion of their digital imagery provider, Image Scans Inc. of Denver, Thornton has added ESRI's GRID module for rectifying imagery to existing vectors.

Finding and Buying Information
Finding base and additional layers already created for others was critical to Thornton's being able to show a quick turnaround from GIS. Maydew became adept at expanding the system "without using the three letter phrase GIS." Thornton purchased their base layer consisting of rights-of-way and easements from the local gas and electric utility, Public Service Company of Colorado. Thornton and Public Service found each other. Lynn Ashley, the GIS technician, used this data as a base for digitizing approximately 20,000 parcels.
      At that point in time, Public Service had 15 years and multiple millions of dollars invested in the creation of this data layer. Subsequent to Thornton's purchase, Public Service has sold the same layer to other municipalities.
      Harrison Resources of Fort Collins, Colo. provided data on congressional districts and soil types. The Colorado State Engineers Office and the University of Colorado provided data on water resources. Older maps were the source on floodplains.
      On an ongoing basis, the Thornton GIS is updated on parcel ownership by the Property Data Center and title insurance companies. Developers are required to submit ARC/INFO compatible files on proposals. An outside consultant, Berger and Co., is used for both custom programming and providing GIS administration for departments too small to have an internal GIS resource.
      When the county and state are ready, Thornton will become one of their data suppliers. Thornton wants to supply the data layers in cooperative agreements with the county and the state, where the currency of trade is additional information.

Aerial Imagery
An excellent example of value from existing information, is Thornton's methodology of adding a raster layer of visual information. As Maydew observes, "Seeing information pictorially is extremely helpful for the non-GIS professional." Since Thornton has made a commitment to a city government wide implementation, a lot of non-GIS professionals need to use the GIS. In addition, applications such as Economic Development and Community Development presentations, park pavilion registrations, and crime scenes, could not be done without aerial images.
      Thornton went to bid three times for the addition of a digital orthorectified layer of raster images. The best proposal, which included various layers such as 4' contours, was $180,000. When the GIS is being implemented without a line-item budget, $180,000 is impossible.
      Thornton contacted Image Scans Inc., one of the few aerial film scanning speciality service bureaus in the world. Image Scans was able to secure the needed images from two different overflights of areas immediately south and north of Thornton.
      The difference in the scales of the two sources of film was digitally corrected so that the appearance was identical. The ground pixel size was the constant as the resolution of the scanning was changed on the two different sets of images. The resulting resolution of +/- 5 feet of the 75 images affords Thornton a great deal of detail and zooming.
      Thornton's personnel are currently rectifying images to existing vectors in their parcel layer, using ESRI's GRID software. They use 50 to 60 control points from the existing Public Service data, and from the living database of surveys for other purposes. The image/vector registration is performed by interns, and computer processed overnight. Since the imagery is not used for engineering standard measurements, Thornton is finding the resulting accuracy of less than 5 feet is sufficient for most tasks, and the visual information for applications such as crime scene depiction is readily available.
      When greater accuracy is needed, spot GPS work is done. Thornton's experience with GPS points and surveyors is duplicated in other cities. The loaded, total cost per GPS point from outside vendors could approach $300 to $400. Thornton bypasses this with their own survey crews and GPS equipment.
      Using existing images and simple rather than full orthorectification, Thornton was able to reduce the cost of the raster layer by a significant amount. Since Thornton is much larger now than it was the first time existing images were purchased, this reduction in cost is allowing Thornton to purchase newer imagery of all of the now larger Thornton, and continue forward with a more frequent update schedule.

Steering Committee
The successor to the Better Government Through GIS Commission is the biweekly GIS Steering Committee. Represented at those meetings are MIS, Community Development, Public Works, Utilities, CMO, police departments, city clerk and the outside consultant Berger and Co.
      One of the purposes of these meetings is the coordination of how layers are used by other departments. An example of an additional benefit from an existing layer is police use of sales tax information to find the owners of cited businesses. Thornton is unique in a city wide GIS implementation, versus many larger cities with as many as five separate departmental GIS projects all competing for resources.

Benefits
Many of the anticipated areas of GIS savings are now currently available. As the city continues to expand its GIS database, programming capabilities, and expertise, implementing future projects requires proportionately less effort than starting from scratch.
      Other benefits of the GIS include eliminating ongoing payments for information from outside sources, better growth, and improved service for the citizens of Thornton. With GIS, Thornton is increasing its information self sufficiency. Economic Development is using GIS to demonstrate visually to prospective clients the demographics of potential business sites, and in the near future the traffic flow in these areas. Through mailings automated by GIS, Thornton residents stay better informed about city activities from ice cream socials, to road repairs, to zoning, to utility work.
      Future application areas include using the ESRI Network module for all routing questions from meter readers to patrol cars, Neighborhood Crime Watch, water and sewer line break notifications, and on-line aerial imagery for city employees and visitors.

Conclusion
Thornton's recipe has allowed it to exceed the GIS development rate of much larger cities. With GIS, Thornton is achieving the better government envisioned by the project champions. In the post Amendment 1 era, Thornton is providing better government while many municipalities and counties struggle to provide the same or some acceptable lesser amount of services with the limited funding.
      Thornton is already enjoying what Maydew refers to as, "Reducting the drudgery index." Planning has automated their production of presentation maps and owner notifications, greatly reducing the amount of overtime for meeting preparation. Vendors who are competing for Thornton's comprehensive plan for the next five to 10 years are astounded by the information available to departments at their fingertips, due to the robust GIS.
      GIS across all agencies is still a future goal for most larger cities. Thornton's future is using the GIS to speed the processing of building permits, improve trash pick up, and something that could be very important come winter...improved snow removal.

About the Author:
Michael O'O'Connell is vice president of sales and marketing at Image Scans Inc. in Denver, Colo. He may be reached at 303-477-5234.

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