Mr. Geodesist:

Would you agree that the best positioning results for station POST at the Stumpwater Proving Grounds and for other points connected by LONG GPS vectors to CORS points would pretty much require using the most current ITRF positions for the CORS points and precise orbits in processing the vectors from each CORS to POST?

Once the vectors are solved, I assume that you'd suggest adjusting the vectors in ITRF to get the ITRF position of POST at the same epoch as was used for the CORS. Would you suggest then solving the best fit transformation to derive the NAD83 position of POST using the NAD83 positions of the CORS points, or is there some advantage to transforming the ITRF (epoch xx) vectors into NAD83(epoch xx), then adjusting them by least squares to arrive at POST?

The NGS method used in OPUS individually transforms the vectors into NAD83 before computing the NAD83 position of the station sought, but isn't that done mainly for the purposes of error estimation in the results. The peak-to-peak differences between individual vectors are used in OPUS in computing the uncertainty in the position sought.

Is there any reason why a transformation wouldn't be as good (or better) a method of arriving at the NAD83 position of the point sought?

Best regards,
Kent McMillan, RPLS Austin TX
Modified By Kent McMillan on 12/17/2001 at 12:52 AM