In the 1960's, engineering firms arbitrarily created map sheet reference schemes (or county map layout index) for each county in West Virginia by dividing larger areas into smaller tiles or rectangular grids. A typical tiling scheme was established by subdividing each county into tax districts for rural areas and corporations for municipalities, which were then further subdivided into primary map sheets with its own number system (1 to n), usually at 1" = 400' scale. The different types of map sheet reference systems are identified by the following elements: map orientation, uniform tile size, the correlation of the 1" = 400' and 1" = 100' scale index grids, and whether the primary map sheet boundaries / tiling numbering system are delimited by the district or county boundary.
10.1. Types of County Map Sheet Reference Systems and their Characteristics. 10.1.a. Random Grid. -- Random orientation of tiles; variable tile size; map sheet index grids do not correlate; district boundary defines the limits of the primary map sheet boundaries / tiling numbering system.10.1.b. Modified Grid. -- Tiles oriented true north; variable tile size; map sheet index grids do not correlate; district boundary defines the limits of the primary map sheet boundaries / tiling numbering system.10.1.c. True Grid. -- Tiles oriented true north; uniform tile size; map sheet index grids do not correlate. Other variations: district boundary or county boundary defines the limits of the primary map sheet boundaries / tiling numbering system; map identifiers either numeric or alphanumeric; map number system from l to n for each district or unique map numbers for the entire county; length and width dimensions of tiles varies from county to county.10.1.d. Subset Grid. -- Tiles oriented true north; uniform tile size; map sheet index grids correlate; county boundary defines the limits of the primary map sheet boundaries / tiling numbering system; map numbers unique for the entire county.W. Va. Code R. § 189-3-10