OPUS v. DPOS
- Thread starter Jim Campi
- Start date
DPOS is still being developed so your question is good to see. Also, there are two avenues, one directly through JMT and your mobile device and the other through your web browser. The backbone of DPOS in both instances is Justin whereas OPUS has two different programs running either OPUS-Rapid Static or OPUS Static. There are other factors employed in both OPUS and DPOS that the user needs to be aware such as DPOS will process GLONASS data when the IGS orbits are available and OPUS won't. Also, at present, the user cannot specify which CORS to use/exclude from its calculations in DPOS, but you can (and should) using OPUS. In brief, the answer to your question is you may see many differences for various reasons including those mentioned above. Frequently for my personal efforts in vetting OPUS and/or DPOS is to use third party software (Topcon Tools Demo) as well as a PPP service; e.g., CSRS PPP. Unlike all of the other methods mentioned, the PPP doesn't use vectors from other CORS and can even handle L1 alone through its modeling of the environmental factors in play.
The attached reports will give you some examples of the differences seen all predicated upon the same data file. Note the horizontal positions between OPUS and DPOS are less than 1cm, and that the differences in ellipsoid height are less than 2cm. In 8 out of 9 values, the PPP values fall between DPOS and OPUS.
ppp 9.330, .390, .542
opus 9.327, .393, .519
dpos 9.342, .389, .525
The attached reports will give you some examples of the differences seen all predicated upon the same data file. Note the horizontal positions between OPUS and DPOS are less than 1cm, and that the differences in ellipsoid height are less than 2cm. In 8 out of 9 values, the PPP values fall between DPOS and OPUS.
ppp 9.330, .390, .542
opus 9.327, .393, .519
dpos 9.342, .389, .525
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Jim Frame
Well-Known Member
How do I get to the DPOS web browser interface? When I click on the big DPOS box at http://javad.com/jgnss/index.html, the only options I see are to use the iOS or Android apps.
My bad... it's still being kept under wraps until the PLS team, Javad or Eugene declare it ready. It's working in beta pretty well now; however, the user at present still can't do certain things that can otherwise be done by OPUS, noting in particular, the explicit inclusion or exclusion of named CORS. This is a pretty important aspect for general purposes in dealing with OPUS, and making side by side comparisons (like above) critical. The workaround illustrated above was to do DPOS first and then OPUS second using the automated CORS choices of DPOS. This example set above, also illustrates another beta-not-quite-ready-for-public-use aspect in that the one CORS that DPOS chose (PNB5) is GPS only.
Jim Frame
Well-Known Member
FWIW, the text adjacent to the OPUS base station selection box now says "NOTE: the automated selection of base stations has recently improved; this option should now be used only sparingly."
That's been there a while and no explanation as to what sparingly means. I never use OPUS without employing the explicit call for CORS I want used for Static; Rapid Static is separate and generally scarfals up everything within 68km or something, but it's still a crap shoot. Without explicitly specifying which CORS that OPUS should use, the results/ abortions are wildly unpredictable.
Jim Campi
Active Member
Thanks Kelly,
Do you know why the error points reported on the radar graph in the ppp solution tend to spiral in a clockwise direction toward the origin? In other words is there any significance that you immediately see? Not looking for a theoretical analysis that requires you to go to referance materials.
If you're referring to a priori position and the diagram above, I'm uncertain but think our best answer will be given by Victor or Vlad. And I also wonder if the latitude of the position enters into the direction of the spiral.