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First, it uses a simple Cartesian coordinate system to specify locations rather than a more complex spherical coordinate system (the geographic coordinate system of latitude and longitude).

Its popularity is due to at least two factors. The system is widely used for geographic data by state and local governments. There are 110 zones in the contiguous US, with 10 more in Alaska, 5 in Hawaii, and one for Puerto Rico and US Virgin Islands. Each state contains one or more state plane zones, the boundaries of which usually follow county lines. “ The State Plane Coordinate System (SPS or SPCS) is a set of 124 geographic zones or coordinate systems designed for specific regions of the United States. State Plane Coordinate Systems are widely used for geographic data, and are based on a flat earth 'plane surveying' methods with simple XY coordinates: ” State Plane Coordinate Systems and NAD83 It defines the origin and orientation of latitude and longitude lines. A datum provides a frame of reference for measuring locations on the surface of the earth. “ While a spheroid approximates the shape of the earth, a datum defines the position of the spheroid relative to the center of the earth. ” DatumsĪ Datum is an anchor point which ties two different coordinate systems (geographic and projected) together.įrom Datums by ArcGIS ( Archive) we read: Unlike a geographic coordinate system, a projected coordinate system has constant lengths, angles, and areas across the two dimensions. “ A projected coordinate system is defined on a flat, two-dimensional surface. ” Projected Coordinate SystemĪ Projected Coordinate System is a planar coordinate system.įrom What are Projected Coordinate Systems? ( Archive) by ArcGIS: A GCS includes an angular unit of measure, a prime meridian, and a datum (based on a spheroid). A GCS is often incorrectly called a datum, but a datum is only one part of a GCS. “ A geographic coordinate system (GCS) uses a three-dimensional spherical surface to define locations on the earth. 8 Classified Coordinate TransformationsĪ Geographic Coordinate System is a spherical coordinate system which uses longitude and latitude.įrom What are geographic coordinate systems? ( Archive) by ArcGIS:.7 Basic Idea Behind Geographic Coordinates.6 Spherical Coordinates Projected To a Plane.