Geodetic Coordinate Systems in Florida: GPS Contribution

Measurements and results derived from the three-dimensional Global Positioning System (GPS) are more accurate than classical geodetic observations and methods used until recently to define conventional horizontal (geometric) da-tums, e.g., the North American Datum of 1983, the final readjustment of which was finished in 1986, thus the notation NAD 83 (1986). The situation may not be strictly the same with respect to vertical (physical) datums such as the National Geodetic Vertical Datum of 1929 (NGVD 29) because an accurate geoid is required. In this paper comparisons of standard datums [NAD 83 (1986), NGVD 29] with recent GPS results in the state of Florida are analyzed. Their relationship with a very long baseline interferometry (VLBI) reference frame is also discussed. The investigation shows that overall the relative accuracy of NAD 83 (1986) in Florida is between 1 200,000 and 1 500,000 or from five to two parts per million (ppm), yet still not as good as the two-dimensional results derived from GPS.