[Proj] Help translating NAD83 coordinates to WGS84

Norman Vine nhv at cape.com
Mon Sep 20 13:23:26 EDT 2004

John D. Evans writes:
> Can someone point me to an authoritative, published (pref. online)
> reference that states an upper bound on the difference between NAD83 and
> WGS84 over North America?

NOAA Professional Paper NOS 2, Article 22. Page 249


Charles R. Schwarz, Editor
National Geodetic Survey

Charting and Geodetic Services

National Ocean Service
Rockville, MD 20852
December 1989

online @


22.2.4 Computational Differences

There are some differences between NAD 83 and WGS 84 which may arise because of approximations made in a particular method of
computing coordinates. For most applications, the effect of these approximations is considerably smaller than the effect of
observational errors. These differences are important only if one is testing the accuracy of a set of equations or a method of
computing coordinates.

One such set of approximations concerns the different ellipsoids used for NAD 83 and WGS 84. This difference has no effect on the
three-dimensional coordinates of a point computed by satellite surveying. If such a set of three-dimensional Cartesian coordinates
is converted to latitude and longitude using the two coordinate systems, there would be no difference in the longitudes, and the
latitude difference would be

which reaches a maximum value of 0.000003 second of arc (or 0.0001 meter) at a latitude of 45 degrees. It is assumed that most users
will ignore this very small difference.



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