sometimes trying to eek out a good shareable solution is like polishing a turd...../rant off
#IfThatTreeWasInTheRWItWouldBeDOWN
Trying to find GPS suitable marks. can be frustrating, and the one you hoped would work just doesn't quite do it.
The most survivable of the old marks are on or too close to public buildings.?ÿ Next most are along railroads too close to the track or if the rr is gone then trees have grown over the culvert or bridge abutment.?ÿ
I haven't had much success massaging the data to rescue a marginal session. Look at the teqc 18s file and see if deleting a mostly unusable sat will improve the stats.?ÿ But if all the sats have bad multipath it's probably a lost cause.
I don't know whether shopping for CORS works or not.?ÿ If you pick or exclude CORS does NGS reprocess the share at some point with auto select?
"A priori" is an assumption you will find and occupy the known point. never before heard it as "a priority".
An occupation with poor sky view blocking satellites in some quadrants cannot be improved by any number of CORS because the satellite geometry in the solution cannot improve beyond those seen in the rover vs. CORS. The typical problem is not necessarily multipath, but is no path.
Your best chance to rescue?ÿ a marginal session is to break your OPUS into multiple small not overlapping sessions, submit to OPUS-RS and possibly discard the poorest solutions, then meaning the rest. This implies you have a receiver that has clean C1/P1 & C2/P2 observations and you know how to edit your RINEX file. If necessary to get clean data, do not hesitate to create a 7.5 or 10 minute files.
If the poor observation is due to closeness to a wall, be aware that your solution may have a positional bias that is normal to that wall. Let us say that you have a second observation that is more or less normal to that same wall, then from that second position you could have some confidence in an azimuth to the first. If your second observation is more or less parallel to that wall you could have some confidence in a distance to that point. That is some useful information being better than no information.
If you are out gathering GPS observations you may not have a total station, but you should always have a tape. Simple lay out offset observations in a simple triangle. Observe your benchmark, offset 1, offset 2 and reobserve the benchmark. In the time of one OPUS observation you instead have four 1/2 hour OPUS-RS observations. Yes, you are going to have to wait to solve, up to two days for clean OPUS-RS data to populate the CORS network, but hey, you were going nowhere in a hurry with the bad observation anyway.
Paul in PA
never before heard it as "a priority"
I believe the OP was referring to Priority A marks in the GPS on BM program.
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