Most state plane zones are based on either a Transverse Mercator projection or a Lambert conformal conic projection. The choice between the two map projections is based on the shape of the state and its zones. States that are long in the east-west direction are typically divided into zones that are also long east-west. These zones use the Lambert conformal conic projection, because it is good at maintaining accuracy along an east-west axis. Zones that are long in the north-south direction use the Transverse Mercator projection because it is better at maintaining accuracy along a north-south axis. One part of one state, the panhandle of Alaska, uses the Oblique Mercator projection, since that region lies on a diagonal.
Even though computer processing power has improved radically since the early days of GIS, the size of spatial datasets and the complexity of geoprocessing tasks being demanded of computers have also increased. Thus the state plane coordinate system is still useful.
Originally, the state plane coordinate systems were based on the North American Datum of 1927 (NAD27). Later, the more accurate North American Datum of 1983 (NAD83) became the standard (a geodetic datum is the way a coordinate system is linked to the physical Earth). More recently there has been an effort to increase the accuracy of the NAD83 datum using technology that was not available in 1983. These efforts are known as "High Accuracy Reference Network" (HARN) or "High Precision GPS Network" (HPGN). In addition, the basic unit of distance used is sometimes feet and sometimes meters. Thus a fully described coordinate system often looks something like: "Washington State Plane North, NAD83 HARN, US Survey feet". This information is needed in order to accurately transform data from one coordinate system to another.
Finite elements, roman-style: a very professional corps of ancient engineers made a lasting contribution to Western civilization.(aqueducts)
Sep 01, 2003; AT FIRST GLANCE, the most striking feature of a Roman aqueduct is the mathematical precision of the arches. These structures are...