Is OPUS only for L1/L2?

They were working on one, but it has never come through. OPUS is only for L1/L2 data.

The other option is to download the CORS stations and post process against them in your package.

On the other board, there was much discussion of L1 VLBL and the results from very distant CORS stations (greater than 100KM) and measured against OPUS. If memory serves, the results were negligible for longer sessions (less than 0.02' horizontal). Should you have CORS stations close, your occupation time is less obviously.

Thales had the three promarks that Dave Karoly and others use. For me, had I bought them, I was going to use one as a "BASE" and rover with the other two in a kinematic fashion and process them against one another. The "BASE" would have been processed against CORS stations to bring in NAD 83 (CORS96) Epoch 2002.0 values to the site. I'm fairly close to several CORS stations and 8 hours of data should have been more than enough.

Other than that, I'm not aware of a work around.

Thanks Kris.

OPUS-GIS Will Be L1

Until then Ashtech has a VRS reference station format in GNSS Solutions. Once you download your Ashtech L1 receiver into Solutions you pick the VRS option, Solutions goes on the internet selects CORS that surround you L1 position and downloads files. It then computes a virtual L1/L2 position near your L1 observations then computes the short range L1 only vectors to your observation points and gives you results.

Without knowing your hardware/software capabilities I do not know what else to suggest.

Several years ago I took some L1 only files and fabricated L2 observations to go with them and submitted and leceived OPUS-RS positions. I was successful in getting results only about 1/2 the time and the program needed considerable more work to get it to a 90% success level which would have made it worthwhile to share with others for improvement. Since I have L1/L2 receivers it was never worth extra effort beyond the educational value I received.

I am pretty certain that OPUS-GIS would be on a format similar to the Ashtech VRS method which is along the lines of RSGPS which is the software within the OPUS-RS method.

Paul in PA

OPUS-GIS Will Be L1

Thanks Paul.

I was talking with Loyal the other day. OPUS is L1/L2 only and will no do L1 only solutions. Turns out that you probably shouldn't use any stations closer than something about 15 Km when sending it to OPUS. If you do the float solutions (instead of L1) will actually downgrade the solution.

Short-Range OPUS

I should probably clarify what Leon said above.

PAGES will solve an L1-FIXED baseline, but OPUS doesn't default to that solution based on vector length (like some commercial processors do). When you run PAGES-NT, you can manually "force" (select) an L1 solution, and that's generally recommended on "short baselines."

I have found that on good static observations (4+hours), that baseline solutions from OPUS seem to work the best between about 50 and 500 kilometers. I just ran four [multi-submission] OPUS solutions today, and on one of the sites, I threw out ALL-THREE of the short baselines (33-68 kilometers) and used the longer solutions (6 baselines ranging from 81-366 Km). This observation was 7h13m so it was about an average occupation for me.

Loyal

Short-Range OPUS

Howdy,

An L1-only solution in PAGE-NT can ONLY be created after first computing an ion-free solution. The PAGE-NT tool uses the combination of different frequency data for cycle-slip correction and to calculate integer bias ambiguities. The use of multiple frequency combinations (L1, L2, L3 (ion-free) and L4 (wide-lane)) allows for significantly more robust integer determination than single frequency.

Cheers,

DMM

Short-Range OPUS

Thanks for the additional information Mike. It's been quite a while since I used PAGES_NT, and I wasn't trying to be too detailed in my comments above.

I have found that the "standard" OPUS vector solutions on "short baselines" are somewhat less "accurate" (or maybe I should say..more noisey) than L1 only solutions in most (but NOT all) cases. It isn't a large amount, but it's enough (sometimes) to "pollute" an otherwise very solid solution.

Of course now that we are moving back into a Solar Maximum period, L1(only) will become increasingly problematical for a while.

Loyal