Implementing NGS Draft Guidelines for GPS-Derived Orthometric Heights

The need to determine accurate heights relative to the North American Vertical Datum of 1988 (NAVD 88) is more prevalent today than ever before. Projects are no longer isolated unto themselves, or designed in a box. Due to global and regional issues such as the environment, and municipal planning, the need to represent the topographic features of the earth accurately in three dimensions is of primary concern. In the past, it was often cost prohibitive to accomplish this. But thanks to advances in Global Positioning System (GPS) technology and geoid modeling, and the development of guidelines and specifications, it has become cost effective to establish accurate, three-dimensional coordinates practically anywhere they are needed. This paper demonstrates the implementation of the National Geodetic Survey’s Draft Guidelines for Establishing GPS-Derived Orthometric Heights in an aerial mapping project, and discusses the project results.