SNARF Working Group - Report of the Second SNARF Workshop

Eos Trans. AGU, 85(17), Jt. Assem. Suppl., Abstract G21D-01 INVITED, 2004

Evolving from NAD 83

Snay, R
Email: Richard.Snaynoaa.gov
Address: National Geodetic Survey, 1315 East-West Highway,
Silver Spring, MD 20910 United States

Craymer, M
Email: craymernrcan.gc.ca
Address: Natural Resources Canada, Geodetic Survey Division, 615 Booth Street,
Ottawa, ON K1a 0E9 Canada

The development of a stable North American reference frame should influence future positioning activities on our continent not only for scientists; but also for land surveyors, GIS professionals, remote sensing professionals, and others. Although our current spatial reference system, the North American Datum of 1983 (NAD 83), may seem sufficiently adequate for most positioning activities in North America, history has revealed that reference systems need to evolve to keep pace with the ever-increasing accuracy with which we are able to locate points on and near the Earth. These accuracy improvements are driven by advances in geodetic technology and geophysical theory. Indeed, the development of electronic distance measurement (EDM) instrumentation in the 1960s and satellite-based Doppler positioning in the 1970s compelled the North American positioning community to supercede the North American Datum of 1927 (NAD 27) with NAD 83 in the mid-1980s. In particular, the EDM and Doppler observations revealed that NAD 27 positional coordinates contained regional distortions exceeding several meters. The Doppler observations also revealed that the NAD 27 origin was more than 100 km from the Earth’s center of mass. NAD 83 was introduced to correct these NAD 27 shortcomings. No sooner was NAD 83 adopted, than newer geodetic technologies (GPS, VLBI, SLR) and newer geophysical theories (plate tectonics and glacial isostatic adjustment) came along to expose some of its shortcomings. For example, it is now known that NAD83 is offset from the geocenter by about 2 m. Here we examine the status of NAD 83 to consider how we may develop a better reference system for North America.

Last modified: 2019-12-24  02:12:53  America/Denver