Mesa County's Geographic Information System
What makes it work and what makes it unique
The information in the History section is a description of how Mesa County develops and maintains its Geographic Information System. It is not the only way to build a GIS but it is one way to do it for a medium sized County on a limited budget.
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Accuracy of Data
GPS controls our data
The geodetic control that Mesa County uses to define the geographic locations of our data started well before a GIS was ever envisioned. During the 1980s the National Geodetic Survey (NGS) placed five HARN (High Accuracy Reference Network) points in Mesa County. The County proceeded to establish the A Mesa County Geodetic Control Network", the largest geodetic control network in the state, based on these five HARN points, using Global Positioning System (GPS) survey technology. The positioning of these points has assisted the County in creating a standardized monumentation grid for public and private surveys as well as setting the stage of control for the development of an accurate countywide digital base map. The County's Engineering Department has continued to build what has been called the SuperNet of over 1000 main control points throughout the Grand Valley. Additional points surveyed using GPS for GIS purposes offer less accuracy, but bring the number of control points to more than 2000. They include PLSS sections and quarter-section points.
Public Works has used GPS for GIS related projects that include: locating road centerlines for over 3000 miles of roadway, geocoding and data linking of County maintained bridges and culverts, and coding utility permit information. Mesa County GIS and other County departments have assisted Mesa State College, CSU Agricultural Extension Office, Center for Disease Control, the Health Department, law enforcement and others with GIS/GPS related projects.
In 1996 Mesa County installed a GPS Community Base Station with a public dial-in BBS which was the only one in this part of the state. This allowed county surveyors and anyone within 300 miles to do post processing differential correction of GPS data without having to setup an additional receiver on an established point. Today 3 CORS base station are running in the County including 1 NGS COOP station to provide high precision/real time system making it possible for surveyors to receive corrected data as they survey in the field without setting up additional receiver/transmitters on high accuracy points. This is the only publicly available system of its type in the western United States. The differential correction data files are now available via the Internet on the County's ftp server.
What does this mean for GIS? It allows the County and others to collect data faster and more accurately, increasing the information we have available and reducing the cost of data collection. GPS has proven to be a fast and low cost method of collecting data and providing the real world control for our GIS. The future of GPS in GIS is becoming more and more obtainable as technology advances and equipment cost declines.
Types of data that are available:
Mesa County has many types of data that have been built, purchased and developed over the years.
Building a Digital Parcel Base
In 1995 when the GIS department (2 people) needed to develop a digital parcel base for the County, we went out to bid to find a contractor to accomplish this project. We had approximately 420 hand drafted assessor parcel maps showing 54000 parcels in 3300 square miles. Within this area the City of Grand Junction had been maintaining a digital coverage (AutoCAD format) for 22,000 parcels in the City and surrounding area of about 45 square miles. We contracted to have the vendor scan, vectorize, build polygons, geocode based on GPS control and build the database for maps outside the City's coverage. The City's AutoCAD files were then combined into the coverage and the County had its first digital parcel base coverage. The entire process took about 1 year. Maintenance and updating has begun on the parcel base and it will soon be the only source of parcel mapping for the County. The establishment of the parcel base has greatly increased the capabilities of the GIS not only for the Assessor's office, but also for other organizations and projects that use data directly tied to parcels. Projects utilizing the parcel coverage include land use studies, County zoning, building permits, future sewer system development, enterprise zone proposals, etc.
Aerial Photography and Satellite Imagery
One of the most used data types that Mesa County's GIS has acquired is digital photography and imagery of the County. In 1994 Mesa County, the City of Grand Junction and other local entities contracted to have the Grand Valley area flown, digitally captured and orthorectified for an area of about 175 square miles. These were black and white photos and were digitally captured at a resolution of Â¼ meter. They are used as background with our vector data for all types of projects from planning to law enforcement.
In 1996 Mesa County began to purchase digital satellite imagery (IRS1C) for the entire County. These are lower resolution images (5 meter) but have proven to be extremely useful for many projects and applications outside the valley area.
In 1997/1998 Mesa County began a joint venture with the USDA (Forest Service) to fly the entire County with high resolution color photography. Mesa County has contracted to digitally orthorectify over 1099 square miles of our populated and developing areas at a resolution of A½ meter.
In 2001 we had a 450 square mile are flown at 1/5 meter in color, in addition we acquired 2 foot contours for a 350 square mile area in the Grand Valley.
- In 2001 we also had the entire County (3300 sq. mi.) flown in B&W at 1 meter resolution.
- In 2003 we had the entire county flown in CIR at 2 foot resolution.
- We have also scanned and rectified many years of historical photos dating back to 1937.
Get started in GIS
Finding low cost and free data
Mesa County has been involved in GIS to some degree since the late 1980's beginning with the Public Works Department. Much of the early GIS data was acquired through state and federal agencies. The first digital data was acquired through the Colorado Department of Transportation and Petroleum Information Corporation which gave the County the opportunity to start developing the first County digital base map. 1990 Census data (TIGER) was aquired and combined with the base map data, giving the opportunity to begin processing data for transportation related projects. Special district data was acquired from the State Department of Local Affairs and additional data was developed in house such as 201 boundaries, voting districts and traffic zones. Mesa County continues to freely exchange data with these organization to develop and maintain up-to-data information.
Make Data Available
A successful GIS must provide a way of making the data available to the end users in a timely and user friendly manner.
When the Information Management Department took over the responsibility of developing and maintaining the county wide GIS in 1995 our goal was not only to develop new source data, but to make sure that the data and tools to access and analyze the information was available to all departments and organizations within the County. Today a state of the art GIS system exists in Mesa County that is available to over 700 county employees in all departments in more than 10 locations throughout the region. Currently there are around 120 active GIS users in more than a dozen departments throughout the County. Our GIS department consists of 2 full time employees. The backbone underlying our GIS begins with the infrastructure that links all information systems in the County.
The County's Wide Area Network (WAN) consist of Novell and Microsoft Storage Area Network (SAN) cluster servers, Unix servers, a 750+ GB GIS file server, a WEB map server, over 800 Pentium based desktop and laptop computers all internally linked by 100 Base-T and Gigabyte internal fiber, broadband connections to the Internet. This allows us to provide access to all the data used by the GIS and other systems to everyone in the County in a fast and transparent method. Other public and private GIS users can down load our data directly off our web site or ftp site at no cost or are provided a CD containing our vector based data set, (over 700 coverage's) at no cost.
GIS not only provides data at via the Internet we also provide online interactive mapping and data retrieval. In 1997 we began a project to automate the Surveyors office by scanning and geo-code all survey related documents including historical plats, subdivision plats and monument records. (at that time over 40,000 documents, today over 4,000,000 have been scan in the County) These documents can now be accesses over the Internet using our interactive mapping and image retrieval tools. Parcel mapping, Zoning, Voter Locator and Aerial Photography can also be viewed on our web site through our interactive mapping programs.
Training and Support
Getting all organizations involved
GIS is not limited to a small organization in one or two departments in Mesa County. The GIS Department provides GIS support to all County departments. This is done through a series of processes, starting with training. Our organization provides in-house GIS training workshops, covering everything from elementary GIS to the development of data for advanced projects. The GIS department also provides support and development for all GIS related projects requested by individual departments. By having the GIS Department in our IS department, we can not only combine resources and avoid duplication of effort as they are related to data collection, but we can address all issues that affect data access, networking and data distribution.
What is GIS (Geographic Information System)?
GIS is an organized collection of computer hardware, software, data and people designed to collect, update, manipulate, analyze, and display many forms of geographically referenced information. It is similar to a traditional Data Base Management System, where we now think in spatial rather than tabular terms, and where the "report writer" now allows output of maps as well as tables and charts. GIS is not simply for building maps, but it allows you to build maps that describe and analyze tabular data.