OPUS tutorial

"Thanks for waiting 12 years to try our OPUS service." -NGS

OPUS

Write down your time, date, INSTRUMENT HEIGHT, type of receiver, type of antenna. Let it run as long as you can + set up you collection on the 30sec to conserve memory

OPUS Is Nice, OPUS-RS Is Much Better

Learn how to break a large file into smaller parts. There are more than enough CORS in an around Indiana to get you an OPUS-RS solution every time.

I broke up a 3 hour OPUS observation from Saturday into 3 files and got much much better solution. 9 CORS versus 3 sure tightens up those numbers.

I pretty much only submit to OPUS on day 1 as a data check and for rough coordinates. I then opened the RINEX file saw that the first 6 minutes while it was gathering satellites were sketchy. I deleted those 6 minutes and then broke it into 3 58 minute observations. I stay in the 45 minute to 1 hour range for OPUS-RS and am genrally very pleased with the results. My results this weekend were so good I did not even resubmit for solutions using rapid orbit, the ultra rapid 18 doing fine.

Paul in PA

Howdy,

If you have a dual frequency receiver and antenna with a phase model, can set up a tripod and measure the height of the antenna reference point accurately, submitting data to OPUS and OPUS-RS is trivial. You do need to insure that your data collection interval is some multiple of 5 seconds. Both these tools accept RINEX files and some native format binary files.

The real trick is understanding the processing report. The two OPUS tools provide different accuracy measures. A peak-to-peak error and a standard deviation are definitely not the same thing.

OPUS-RS is intended for use with session lengths from 15 minutes to two hours. OPUS is intended for two to 24 (or 48) hours.

BTW, if you have RINEX files try the other automated processing tools: AUSPOS (Geoscience Australia), SCOUT (California Spatial Reference Center), CSRS-PPP (Natural Resources Canada) and AAPS (NASA JPL).

Some useful links follow:

http://www.trimble.com/planningsoftware_ts.asp - GPS mission planning software for download
http://asp.ashtech.com/wmp/ - web based tool for GPS mission planning
http://facility.unavco.org/software/teqc/teqc.html - site for translation, editing and quality checking software
http://www.ngs.noaa.gov/OPUS/ OPUS GPS processing tool - NGS processor using web-based form for input
http://csrc.ucsd.edu/cgi-bin/SCOUT.cgi SCOUT GPS processing tool - Scripps Institution of Oceanography (UCSD) ftp-based automated processing tool
http://www.ga.gov.au/earth-monitoring/geodesy/auspos-online-gps-processing-service.html AUSPOS GPS processing tool - Australian processor using web-based form for input
http://www.geod.nrcan.gc.ca/products-produits/ppp_e.php - Online Global GPS Processing Service (CSRS-PPP) of Geodetic Survey Division of Canada
http://apps.gdgps.net/apps_file_upload.php - NASA GDGPS processing tool.

Cheers,

DMM

http://geodesyattamucc.pbworks.com/w/file/fetch/53012749/lab9_2012_summarySolutions.pdf - a summary of a recent submission to these tools.

"OPUS accepts receiver epoch rates of 1,2,3,5,10,15 or 30 seconds, all of which are decimated to 30 seconds for processing."

Not 20 I'm told

Howdy,

You are correct about the 20 second collection interval. This was the default for Ashtech receivers. When GPS software merges data from different receivers they find when data is common to both receivers. If one collects at 15 and the other at 20 seconds, they only have common data every 60 seconds. Sorry for the misleading information.

I believe NGS decimates files observed at a higher rate than 30 seconds during the merge process. I do not think they interpolate at all.

Cheers,

DMM

Deral's rules..

Fixed height rod and check plumb in two directions at the start and at the end of the session. I have a field book and record Unit, height, time started and time ended. Opus does not need this but it will help you later if you are hunting an old file to process again.

Minimum two hours but I always shoot for four or more.

Clear skys, at least until you have studied and learned what the extended output tells you.

If you take four hours or more then take a picture close up on the point and then one at eye level, then a directional photo showing backgrounds. Then you can not only do OPUS but OPUS-DB.

For you first point I'd suggest a marker already in the NGS database. Gives you a check and also if you do the OPUS-DB then you help everyone.

To get to OPUS-DB just go to options and selected publish. A few more step but your datasheet will on their website.

I process using our normal reference frame and then resend selecting the new reference frame. I have a lot of points and building a comparison database at this time.

The field is about as painless as can be, and the submittal is easy as well.

Deral

Thanks bro, et al.