State Plane Coordinate System State Plane Coordinate System 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. Each state contains one or more state plane zones, the boundaries of which usually follow county lines. 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. The system is widely used for geographic data by state and local governments. Its popularity is due to at least two factors. First, it uses a simple Cartesian
Plane wave Plane wave In the physics of wave propagation, a plane wave (also spelled planewave) is a wave whose wavefronts (surfaces of constant phase) are infinite parallel planes. Mathematically a plane wave takes the form in which the arbitrary (scalar or vector) function formula_2 gives the variation of the wave's amplitude, and the fixed unit vector formula_3 is the wave's direction of propagation. The solutions in formula_4 of comprise the plane with normal vector formula_6. Thus, the points of equal field value of formula_7 always form a plane in space. This plane then shifts with time formula_8, along the direction of