how good is an opus solution? Just a quick observation???ÿ
A while back, I carefully laid out a baseline in 30 m stations with a GTS3B and HP3805A, after checking them on a 1km CBL. (Mirror offset separately confirmed.)
A couple years ago I put up a Z-12 on the zero point of my baseline: 90 min collection, whopper antenna, and opus rapid orbit solution.?ÿ
Recently, I set a ZSurveyor on the 30 m station, for about 90 min. Then, weeks later I setup ZSurveyor on the 60 m station.
So 3 opus solutions for each station (0 m, 30 m, 60 m)
Simple inverse of ECEF coords returned:
29.998 m, 30.002 m, and 59.999 m.
The est error reported in the opus solutions is 0.006-007 m.
Didn??t expect that. (And that??s not a one-off, I??ve several short distance EDM v opus checks.) I love Z12.?ÿ
I recently set a mark for a RTK base station on the roof level (7th floor) of a parking garage. You just can't get better sky conditions around here.?ÿ I've observed it 3 times by OPUS. The first 2 were 4hour sessions, the 3rd about 2.5 hours.?ÿ ?ÿ?ÿ
?ÿ
332700_220513?ÿ ?ÿ160276.8510?ÿ ?ÿ 313427.1836?ÿ ?ÿ 253.497?ÿ ?ÿCP BP "SURVEY MARK"
332700_220516?ÿ ?ÿ160276.8581?ÿ ?ÿ 313427.1729?ÿ ?ÿ 253.524?ÿ ?ÿCP BP "SURVEY MARK"
332700_220524?ÿ ?ÿ160276.8875?ÿ ?ÿ 313427.1708?ÿ ?ÿ 253.474?ÿ ?ÿCP BP "SURVEY MARK"
Coordinates are OCRS-Portland Zone in International Feet.?ÿ
When I was measuring my wife's farm I used post-processed base-rover, so had a base on the same point 4 days for 3 or 4 hours each. This was an antique Trimble 4000sse that can record only 9 GPS sats and may hang on to one going away while not switching to another better one that has come into view.?ÿ
All OPUS solutions for the base would fit on a US dime.
@bill93?ÿ
of course a dime. The point was that the ??dime?? sized uncertainty of each solution, in very close proximity to each, returned an inverse distance that was much better. (Well aware that comparing an opus position to a published point is +/- a dime is not bad.)
The scale errors of course are quite near zero. It??s the base error that comes into play when distances are very very short. And the base error in this example was very small. (And never mind the 25 yr old Ashtech with week rollover error.)
1-2 mm at 30 m using baseline post processing sure. I didn??t expect opus to be that good in m-to-m distance. A 5-10 mm, given that opus solutions collected years apart, would??ve not been unexpected. (Thought I??d share for new the persons.)
I did a science project with OPUS X90 on a pillar. We had several of those units that we only used a few times a year. I stored one of the hooked to a deep cycle marine battery, with a charger. On Fridays, as an excuse to get out of the office, I would swap it out. ?ÿI converted that week long file to RINEX, and split it into 12 hour files. On Monday,I would submit all of the files and load the output into an Excel spread sheet. The coordinates agreed within 3 mm in horizontal and 10 mm in vertical. I attributed the vertical variation to the level of the river, about 50 meters south of the pillar. When the river was in flood stage, the pillar appeared to rise 10 mm. I had about 250 observations over 24 months. ?ÿ We had no centering error in this setup because of the pillar. We had an old Wild GDF2 that we leveled with a T-2 using double centering procedure to check the level bubble.
.... an antique Trimble 4000sse....
That hurt a little.?ÿ :-(?ÿ One of my favorite GPS units of all time.
