Spatial Thinking in Planning Practice: An Introduction to GIS

18 Figure 2.6. Visual depiction of the Universal Transverse Mercator project system. http://en.wikipedia.org/wiki/ Universal_Transverse_Mercator_coordinate_system Figure 2.7. "e zones of the Universal Transverse Mercator system as displayed over the United States. http:// en.wikipedia.org/wiki/Universal_Transverse_Mercator_coordinate_system STATE PLANE COORDINATE SYSTEM A second coordinate system is the State Plane Coordinate System. "is system is actually a series of separate sys- tems, each covering a state, or a part of a state, and is only used in the United States. It is popular with some state and local governments due to its high accuracy, achieved through the use of relatively small zones. State Plane began in 1933 with the North Carolina Coordinate System and in less than a year it had been copied in all of the other states. "e system is designed to have a maximum linear error of 1 in 10,000 and is four times as accurate as the UTM system. Like the UTM system, the State Plane system is based on zones. However, the 120 State Plane zones generally follow county boundaries (except in Alaska). Given the State Plane system’s desired level of accuracy, larger states are divided into multiple zones, such as the “Colorado North Zone.” States with a long north-south axis (such as Idaho and Illinois) are mapped using a Transverse Mercator projection, while states with a long east-west axis (such as Washington and Pennsylvania) are mapped using a Lambert Conformal projection. In either case, the projection’s central meridian is generally run down the approximate center of the zone. Chapter 2: Coordinate Systems and Projecting GIS Data