Geographic Information Systems (GIS)

Cleveland County Assessor’s office GIS (Geographical Information System) has been is place since the early 1990s. The department has been using ESRI (Environmental Systems Research Institute) software for its mapping needs from the beginning to the present time. At this time the GIS department only maintains a parcel layer with plans of adding new layers for locating and more accurately assessing property in Cleveland County.

Locating land is fundamental to the tax mapping process. Once land is located it must also be given its own unique "name". This is called parcel identification. A good land description will permanently and distinctly locate one and only one individual parcel of land. In Oklahoma, land is described by written descriptions or legally recorded plats.

Written land descriptions may be based on the rectangular survey system (also known as the township and range system), a metes and bound description or a coordinate description system. This system is based on the idea of parallels and meridians that circle the globe. The equator and all horizontal lines north and s

outh of it are known as parallels. The vertical lines which converge at the north and south poles are known as meridians.

The rectangular survey system also has its own special meridians and parallels throughout the United States. The meridians are known as "principal" meridians. Each principal meridian has a parallel, which goes with it. These are known as "base" lines. The points where these two meet are known as initial points.

In Oklahoma, land described using this system is referenced to either the Indian or the Cimarron Meridians.

Another set of lines is established at 24-mile intervals north and south of the base line and at 24-mile intervals east and west of the principal meridian. The east-west lines are called standard parallels or corrections lines. They are one continuous, uninterrupted line. The north and south lines, called guide meridians, are not continuous throughout their length. Because meridians converge, as they get closer to the poles, they must be broken at the base line and at each standard parallel.

The guide meridians and standard parallels form a 24-mile square. Each of these 24-mile squares is divided into sixteen smaller units of land called townships. A township is, as nearly as possible, six miles by six miles. A row of townships extending north to south is called a range and a row east to west is called a tier. Each township is further divided into 36 one-mile square areas called sections.

Sections can be subdivided as well. The quarter section (160 Acres, 1/2 mile square), the half-quarter or eighth sections (80 Acres, 1/4 mile by 1/2 mile), and the quarter-quarter or sixteenth section (40 Acres, 1/4 mile by 1/4 mile). The quarter-quarter section is the minimum legal subdivision under the general land laws but it is common to divide the subdivision further for descriptive purposes.

Graphic land descriptions are based on the recording or filing of maps. These descriptions are known as "recorded map descriptions" or "legally recorded plats". Record map descriptions are descriptions of parcels by reference to lot numbers (or letters) and/or block numbers (or letters), and name or numerical designation given to a recorded or filed map.