Thanks for the reply! The PennDOT mark J201 was established for a highway project by static dual frequency GPS, (Trimble), and the use of 9 HARN stations. It is a "first order" mark and may be added to the NGS database. The mark is very good fpr GPS observations having mostly clear sky with very few obstructions. I recorded positions by hand from VisualGPSce at 4 minutes, 10, 15, and 25 minutes. An average of the readings yielded a position that was 2.007m slightly south and east of J201. This was an autonomous position with no post processing to any other marks. The elevation was 4.084m lower than J-201's published elevation. Not too shabby!!
At work we have a Trimble GeoXT with pathfinder office for post processing. In really good GPS conditions we can get sub meter reliably. But in a series of mark to mark comparisonc for autonomous positions the BT-339 that I purchased from you folks on April 13, 2006 it outperforms the trimble. That is why I want to try some post processing with it!
Again, thanks for the reply.