Geodetic                                                 

Geodetic surveying measures all elevations from a level surface, and because all instruments use a straight reference plane, this requires all instrument readings of elevation to be adjusted for the curvature of the earth. Geodetic surveys are used when a high degree of accuracy is needed and when the survey will cover long distances or a large area. The two fundamental survey control systems of the United States are the triangulation net and the level net established by the U.S. Coast and Geodetic Survey. These nets cover the entire United States.

The level net is used extensively throughout the United States for surveys of all types, but the triangulation net has been used in the past only for large and important surveys as its use required geodetic reduction. Geodetic reduction is unnecessary for most surveys. To make this net available for surveys of every type, the U.S. Coast and Geodetic Survey in 1933 introduced the State Coordinate Systems. Since 1996 NavTech has been utilizing GPS to tie down our projects to state plane coordinates. This extra step is to assure our clients that their project can be shared with local government agencies and applied to their GIS.