<P> 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 are one - quarter of the older 15 - minute series . On a 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 ( 130 to 180 km ) . </P>
<P> 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 are one - quarter of the older 15 - minute series . On a 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 ( 130 to 180 km ) . </P>
why is it called a 7.5 minute map
why is it called a 7.5 minute map
maps are one - quarter of the older 15 - minute series
maps are one - quarter of the older 15 - minute series