Quadrangle (geography)

In geology or geography, the word "quadrangle" usually refers to a United States Geological Survey (USGS) 7.5-minute quadrangle map, which are usually named after a local physiographic feature. The shorthand "quad" is also used, especially with the name of the map; for example, "the Ranger Creek, Texas quad map". These maps appear rectangular, hence the use of the word "quadrangle" to describe them. On a USGS 7.5-minute quadrangle map, the north and south limits of the quadrangle are not straight lines, but are actually curved to match Earth's lines of latitude on the standard projection. The east and west limits are usually not parallel as they match Earth's lines of longitude. In the United States, a 7.5 minute quadrangle map covers an area of 49 to 70 square miles.

As a specific surveying term, a quadrangle is the basic subdivision of the United States Public Land Survey System. In this system, a quadrangle is an area that can be subdivided into 16 townships, and has limits generally measuring 24 miles on each side, although this distance is not exact due to the effects of surveying and mapping the curved surface of Earth.

The surfaces of other planets have also been divided into quadrangles by the USGS. Martian quadrangles are also named after local features.

Quadrangles that lie on the pole of a body are also sometimes called "areas" instead, since they are circular rather than four-sided.