The National Spatial Reference System (NSRS), which is managed by the National Geodetic Survey (NGS), is a coordinate system that includes latitude, longitude, elevation and other values. The NSRS consists of a National Shoreline, the National CORS (a system of Global Positioning System Continuously Operating Reference Stations), a network of permanently marked points and a set of models that describe dynamic geophysical processes affecting spatial measurements.
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National Spatial Reference System Wikipedia(Text) CC BY-SA