Universal map code. (A 7-1/2-minute quadrangle identification system)

Topographic maps of the USGS 7-1/2-minute quadrangle series are indispensable tools in forestry and land analysis. Increasing use of automatic data processing techniques in the analysis of geographic data produced a need for a computer compatible system of identifying, locating, and filing 7-1/2-minute quadrangle maps. The universal map code utilizes the geodetic coordinate system in which the surface of the earth is divided into one-degree cells. Each one-degree cell contains sixty-four 7-1/2-minute cells (quadrangle). This technical note explains the universal map code, the computer map file, and gives some specific uses of the system.