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GIS Layer Descriptions

Accuracy Limitations & Intended Uses for GIS Data
It is the intent of the County of Tuolumne that the GIS mapping resources be the most accurate and useful we can create and maintain. However, it is very important that users understand the limitations of the information being0 accessed. For example, many of our data sets available are based on parcel data. The parcel data is derived from the assessor’s parcels, which may or may not represent legal parcels. The shapes, angles, and dimensions of these parcels are not exact, and only legally recorded parcel maps should be used for any measurement or design work, not assessor’s parcels or the parcel data sets found herein.

Updating Data
Updating of the parcel data occurs on a periodic basis, and there can be a delay in adding new divisions, mergers, or boundary adjustments to the parcel data set. If you suspect the data shown by a GIS file is not correct for any reason, contact the Community Resources Agency for verification or other assistance as soon as possible. Prior to gaining access to available files, review the GIS layer descriptions for more detailed information about the major data sets found on our map pages.

Cadastral Parcels
Accuracy Statement
Parcel boundary lines are of variable accuracy, but use is intended for a 1:250,000 scale.

Description
The county parcel layer was derived over many years from the cadastral parcel maps prepared by the Assessor's Office. The complete and contiguous parcel fabric was then registered and rectified to the best available Public Land Survey (PLS) available. This PLS layer has many inherent inaccuracies related to the original surveys completed in the late 19th and early 20th centuries. As more accurate ground controls become available, the parcel layer will be adjusted. The parcel layer is currently updated roughly twice per year, based on changes to the cadastral maps by the assessor’s drafting function. This can result in delays of several months before updates due to land divisions, mergers, and boundary line adjustment are reflected in the parcel data sets used by these map pages.

Limitations & Intended Uses
Based on the above limitations, parcels and parcel-based layers should only be used for establishing relationships between parcels, and with parcel-based data such as zoning, general plan land use designations, supervisorial district mapping, and similar data sets derived primarily from the parcels. They are not intended for design use or similar functions that require a higher level of accuracy and precision.

Zoning Districts
Accuracy Statement
Zoning districts are of variable accuracy, but they are intended to be used at a 1:250,000 scale.

Description
The zoning district layer was generated from the county parcel layer, and the zoning district attribute is associated with a polygon representing an assessor's parcels. Tuolumne County has both primary zoning districts and combining districts. It is common to have multiple primary districts, and if that is the case, those zoning districts are separated with an ampersand ("&"). Primary zoning districts can have one or many combining districts, which are always preceded with a colon (":"). For example, the most common zoning district in the county is R-1:MX, which means the primary zoning district is R-1, with an :MX combining district. It is also quite common to have some open space (O) on the property. In order to determine the distribution of O or other zoning districts on the property, you must contact the Community Resources Agency. This web-based tool only indicates what zoning districts are on a property, not how much or where the boundaries may be. Detailed explanations of the intended and allowable uses for the zoning districts are found on Title 17 of the Tuolumne County Ordinance Code. A summary table that defines the intended density limits of the various zoning districts and relationship between the districts and the general plan land use designations is included with the zipped file.

Limitations & Intended Uses
Review the limitations and intended uses for the parcel layer and the description above. The zoning districts are attributes to the assessor’s parcel number, and in the past we have found occasional errors. Those have been corrected, and we intend to maintain this information as correct and current as we can. Zoning districts do change over time, and there could be minor delays in updating the tables on which these attributes are based. If the information provided by this tool is at all suspect, please contact the Community Development Department immediately with the assessor’s parcel number, and we will verify the data for you. Especially if information derived through these mapping tools in any way contradicts information you received from other sources, possibly including this department, it is your responsibility to check with the department for confirmation prior to making any economic investments or plans. This will give all involved an opportunity to ascertain the accuracy of the given information and, if necessary, allow us to improve the accuracy of our data sets for future users.

Supervisorial Districts
Accuracy Statement
Supervisorial district areas are accurate at a 1:250,000 scale.

Description
The supervisorial district layer was generated primarily from the county parcel layer, and secondarily from the roads data set to indicate the boundaries of the five supervisorial districts in the county. Please see the statements concerning the parcels and roads about accuracy and other details.

School Districts
Accuracy Statement
School district areas are accurate at a 1:250,000 scale.

Description
The school district layer was generated primarily from the county parcel layer based on tax rate areas as defined as attributes to the assessor’s parcels, and secondarily from the roads data set to indicate the boundaries of the school districts in the county. Please see the statements concerning the parcels and roads about accuracy and other details.

General Plan Land Use Designations
Accuracy Statement
General plan land use designations are accurate at a 1:250,000 scale.

Description
The general plan land use designation layer was generated primarily from the county parcel layer, and most of the land use designation polygons are built from one or many assessor's parcels, although some parcels do have multiple land use designations within their boundaries. For more detail concerning the intended or allowable land uses according to the designations, consult the land use element of the Tuolumne County General Plan. A copy of that document is found within the overall zip file for this layer.

Limitations & Intended Uses
Review the limitations and intended uses for the parcel layer. In addition, the land use designations found using the Web-based mapping tools are using the same data sets as used by the Community Resources Agency. However, if information derived through these mapping tools looks suspect or in any way contradicts information you received from the department in another way, it is your responsibility to check with the department for confirmation prior to making any economic investments or plans in order to ascertain the accuracy of the given information.

Airport Land Use Compatibility (ALUC) Plan Zones
Accuracy Statement
ALUC plan zones are accurate at a 1:250,000 scale.

Description
The ALUC plan zones layer was generated primarily from the county parcel layer and secondarily from the roads data set to indicate the airport land use zones associated with the two airports in Tuolumne County: Columbia Airport and Pine Mountain Lake Airport. Please see the statements concerning the parcels and roads about accuracy and other details. The nature of the zones and associated limitations to future development are defined in the ALUC Plan adopted by Tuolumne County. A copy of that approved plan is included within the overall zip file for this layer. Any questions about the zones or the plan should be directed to the Tuolumne County Community Resources Agency.

Voting Precincts
Accuracy Statement
Supervisorial district areas are accurate at a 1:250,000 scale.

Description
The Voting Precinct layer was generated primarily from the county parcel layer, and secondarily from the roads data set to indicate the approximate location of the boundaries of the voting precincts in the county. Please see the statements concerning the parcels and roads about accuracy and other details.  Any questions concerning the applicable voting precincts for any properties in the County, particularly those on or near the approximate boundaries should be directed to the Tuolumne County Elections Office.