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1. What is a Geographic Information System (GIS) and why is it important?

GIS is a system or technology that manages, analyzes, and disseminates geographic knowledge. In Tuolumne County, the GIS is used to create maps and perform analysis using information related to properties, zoning, roads, addresses, locations of various features, and other geographic information. It is also a critical tool used in Dispatch to speed the time it takes to respond to 911 call or other incident. For a more detailed description of GIS technology, we recommend that you visit: What is GIS

2. What map tools are available to the Public

The GIS webpage gives you links to the map viewers that are currently available. We are working to add new ones and improve the existing viewers and will post the new/improved map tools as soon as they are ready. Within each of the viewers are icon-based toolsets, and help in using those is found by clicking the info icon.

3. Why do you insist on making me see the initial page and click on "I agree to the terms and conditions” prior to getting access to a map viewer?

We work with the datasets constantly and strive to make the data as accurate as we can. However, we understand that there are limitations to how the information should be used because of the variable accuracy and completeness of the data, and hope that reading the disclosure information will cause the public user to understand the limitations. Actively checking the results with this Department prior to making a further investment of time or money is strongly recommended. 

4. How accurate are the GIS layers, can I use them in design work?

None of the GIS layers have been prepared to meet Survey or Engineering accuracy and should not be relied upon in design work. The horizontal accuracy of the individual layers varies widely, and sometimes the accuracy of different areas of the same layer also varies widely. The use is intended for planning-level work, to show the overall spatial relationship between features suitable for large-scale or broad-brush viewing and analysis.

5. One or more of the map viewers fail to open on my computer/Ipad/Phone. Why?

We have prepared map viewers based on two types of application builder software: Javascript and Flex. The Javascript viewers employ the basic layers should work on most computers, so long as your browser security allows it to work (check your pop-up blockers and turn them off). The Adobe Flex viewers do not work on most Apple devices like Ipads and Iphones. However, the Flex app is much more powerful and allows us to deliver more layers and tools with better customization so we are going to continue using it unless a better alternative arises.

6. I have GIS software and want a copy of your data files; how do I do that?

We periodically export files from our database and make them available for download by GIS users as shapefiles. The procedure to get access those files is described on the GIS File Access page.

7. Are all of your GIS layers viewable with the map viewers, or as downloadable copies of your data files?

No. Some layers used by certain in-house users are considered confidential and are not available. Although the parcel layer is based on the Assessors’s Maps, the ownership and some other data maintained by the Assessor’s Office can only obtained from them directly, so those data are also not publicly available through GIS.

8. Why does it take so long for the map viewers to load on my computer?

Map tools and data-sets are inevitably large, complex files, which can take a long time to load when you are using a slower dial-up connection. We try to balance the file size and load time with the desire to make the tools easy to use and powerful. If we can improve the viewers and make the load time shorter, we will do that in the future.

9. Why do you insist on making me see the Acknowledgement of Accuracy Limitation and Intended Uses for GIS Data page and clicking on I Agree prior to getting access to a map viewer?

We work with the data-sets every day and strive to make the data as accurate as we can. However, we understand that there are limitations to how the information should be used because of the variable accuracy and completeness of the data, and hope that reading the disclosure information will cause the public user to understand the limitations.

Actively checking the results with this department prior to making a further investment of time or money is strongly recommended. If we can set the acknowledgement page in a cookie form or similar that would make you only click the I Agree button once and then remember, we will do so in the future.

10. How do I ask a question?

Like all of the major webpages for Tuolumne County, the GIS page has contact information on the side. Ways of using the contact information to ask a question include a phone number, address, and a link that allows the user to send an email to us. We try to answer any inquiry in a complete and timely fashion.

11. How can I print pages or maps from the map viewers?

As we are able to devise Printer tools that allow the user to print a map directly from the viewers, we will enable those and put print icons on the viewer interface. Without those, the user will have to use a “Print Screen” process to copy the image of the map within the viewer to another application to print.