Current through Register Vol. XLI, No. 50, December 13, 2024
Section 189-3-4 - Map Elements A manual or automated mapping system for assessment purposes includes the following elements: geodetic network, mapping layers, parcel identifiers and attributes.
4.1. Geodetic Network. -- The geodetic control layer provides a common reference system for establishing coordinate positions of all geographic data. This is coordinated and managed by the National Geodetic Survey and provides a consistent and uniform definition of coordinate systems, datums and monumented points across a jurisdiction.4.1 .a. Datums. -- The horizontal datum shall be the North American Datum of 1983 (NAD83) and successive adjustments; the vertical datum shall be the North American Vertical Datum of 1988 (NAVD 88).4.1 .b. Coordinate Systems. -- The State Plane Coordinate System (map units in feet) is recommended for the input, storage, and exchange of map data. Counties shall map in the correct "South Zone" or "North Zone" of the State Plane Coordinate System as prescribed in W.Va. Code § 30-13A-17. The Universal Transverse Mercator Coordinate System (map units in meters), Geographic Coordinates System (map units in decimal degrees), and other coordinate systems and projections may be used to satisfy special requirements.4.2. Map Layers. -- The base map layers provide a physical framework upon which non-physical parcel information can be displayed. A full multipurpose cadastre will have additional map layers. Index layers provide a geographic reference to the individual tax map sheets. 4.2.a. Base Map Layers. -- Base map layers, such as aerial photography, boundaries, roads and streams, are the typical foundation layers of a cadastral mapping system. Base layers are tied to the geodetic control and are usually derived photogrammetrically from aerial photographs. 4.2.a.1. Horizontal Accuracy. -- All new or revised base map layers of physical features shall meet or exceed a horizontal accuracy scale of 1:4800, or + or -13.33 feet, in accordance with National Map Accuracy Standards.4.2.a.2. Scale Mixing. -- The mixing of digital map data of widely divergent scales into a common database shall be avoided, as the positional accuracy of the aggregate database is considered to be no better than that of the smallest scale. If digital map layers are derived from different sources, then efforts shall be employed to improve the compatibility of map layers with one another, including the spatial adjustments of specific layers to a more accurate base map.4.2.a.3. Existing Digital Data. -- Before creating new base map layers, the availability and suitability of existing digital data from the State Geospatial Data Clearinghouse or other sources should be checked.4.2.a.4. Official Boundaries. -- The official county boundaries (W.Va. Code § 7-2-6) and tax district boundaries (W.Va. Code § 11 -3-1a) are derived from the 1:24,000-scale U.S. Geological Survey's topographic maps and are digitally available from the State Geospatial Data Clearinghouse. The official corporation boundaries originate from partnership efforts of the municipalities and U.S. Census Bureau.4.2.b. Cadastral Map Layers. -- Cadastral mapping layers are the property and lot lines, set forth dimensions and/or areas, and other parcel-related geometry that assessors are required by state law to collect and maintain. Parcels and related layers may be compiled by digitizing scanned tax maps, coordinate geometry, or by other reliable sources.4.2.c. Additional Map Layers. -- Additional map layers such as zoning, flood hazard areas, soil type, and other layers may be obtained and utilized from other offices or entities to extend the value of the mapping system.4.2.d. Index Map Layers. -- Index map layers show the location and boundaries of the individual tax map sheets in relation to major features (major highways, populated places, etc.) within the jurisdiction. Index layers shall be used to prepare index reference maps of the entire county and other subdivisions (e.g., tax district, corporation, or map blocks), showing specifically the area covered by each tax map sheet and its geographic relationship to the other individual tax map sheets.4.3. Parcel Identifiers. -- Each parcel shall have assigned to it a unique identification number that links each parcel boundary with the assessment database. Details on parcel identification systems are in section 9.4.4. Parcel Attributes. -- It is recommended that parcel geometry be linked or cross-referenced to ownership and assessment information centrally stored in the Integrated Assessment System.