If I have two receivers and want to use them in a base/rover fashion with no radio link, is there any free service or software for post processing vectors?
My idea is to write a program to filter the RINEX files to contain only the satellites at each epoch that both receivers recorded (see other thread about manipulating RINEX). Then submit minimum-length OPUS-RS runs and take the difference of the resulting positions as the vector. Add the vector to the long session at the base to get rover position.
This should give a more accurate vector than comparing results from everything the receivers captured, assuming they have enough in common.?ÿ The proprietary software must do something similar.
What sort of vector accuracy would you expect from this procedure under open sky?
I don't know of any OPUS processing that would connect with the rover if we are discussing short session times, but it will with the base, from there you control the rover locations, or use CORS data to process the base and the rover; sub cm for the locations. Basically you are wanting to do static on the rover from the base or from CORS data, you can then adjust the vectors to the rover antenna, if you wish to have multiple vector solutions. As always way more important to get multiple sessions on any point.
It's done all the time in my Trimble software which is far from free, maybe a demo version of one of the vendor's software will do that.
I have software I have purchased or it came with receivers I purchased that has always done that. It was not expensive so I never took the costly time to look for something free. Pretty much you leave all the data in there, common or not and let the software use what it considers best. Because of the many short files in the rover receiver sometimes one or more satellites does not get properly resolved. On occasion you may have to remove it but I have found out afterwards that that bad data was already being ignored. My software informs me of the number of common satellites used and the PDOP. It is easy to see if you actually had to get involved.
If you own certain receivers the original agreement included the right to use specific software which may be out there to find. Other manufacturers required you to pay for everything and every upgrade.
Whether or not you have a base and a rover, your best bet is to find software that can create a VirtualReferenceStation. A created VRS base point file is free of any obstructed satellites that may have occured with an actual receiver in the field.
Paul in PA
Paul, your software was probably not expensive in the context of a professional business, but I don't make any money for playing with this stuff.
If you're content to process only L1 signals, I think you can get a free copy of Ashtech Solutions.?ÿ Probably could get a few others, too, if you're content with L1 only.
I hope that someday OPUS Projects will be able to process short observations, maybe a 15 minute ?ÿfile, our even shorter for short baselines.?ÿ
I hope that someday OPUS Projects will be able to process short observations, maybe a 15 minute ?ÿfile, our even shorter for short baselines.?ÿ
I got Topcon Tools (thanks @totalsurv) to import two simultaneous GPS sessions and give me much lower sigmas for the vector between them than for the points.?ÿ Some further checking is in order, but that's progress.
They were both "static" sessions.?ÿ Do I need to select a different mode to get the best results?
Do I understand correctly that this processing used broadcast orbit data from the receiver files, and I could download a rapid or precise orbit file later to improve the positions??ÿ
I'm thinking that while better orbit data would improve the positions, it wouldn't give me any significant improvement for a vector of a few km. True?
Do I understand correctly that this processing used broadcast orbit data from the receiver files, and I could download a rapid or precise orbit file later to improve the positions??ÿ
I think the Import from Internet option under the Jobs menu should let you download the precise ephemeris.
Did you hold one point for horizontal and vertical Control?
You can import a raw or rw5 file from a total station, then edit the data.
Right now I'm concentrating on getting the most accurate vector I can. For that i wouldnt constrain the base coords, and would want the sessions to use the same times and satellites.
Then I would hold the base coordinates from a long OPUS static session and apply the vector to the other station.
Bill,
You may want to check out RTKLIB: An Open Source Program Package for GNSS Positioning
Don't' let the name fool you, it actually does Post Processing of Static data, with an included software called RTKPost.
It supports standard and precise positioning algorithms with:
GPS L1, L2, L5, GLONASS, Galileo, QZSS, BeiDou and SBAS
It supports various positioning modes with GNSS for both real?time? and post?processing:
Single, DGPS/DGNSS, Kinematic, Static, Moving?Baseline, Fixed, PPP?Kinematic, PPP?Static and
PPP?Fixed.
The name had fooled me, and it does look interesting. Thanks.
I am making progress on learning to use Topcon Tools demo mode, but have also gotten my program working to process two Rinex files with overlapping epochs, and output two corresponding files containing only the common epochs, or only common epochs and their common satellites.?ÿ That gives me files to compare to T.T. so I understand better how it works.
Bill93, I believe Trimble Geomatics Office is free off the internet.?ÿ That's a full blown system.?ÿ Ooops, you'll have to "Fix week" your files if you go the TGO route.