Hybrid RTK. Post Processing in the Field.

Shawn Billings

Shawn Billings
5PLS
Today I enjoyed my first successful Hybrid RTK project with DPOS.

I set up a Triumph 1 base with Base Rover Setup broadcasting very low power. I collected five points with raw data. The first point received corrections producing a fixed solution. The remaining four points were standalone. I sent the project to the new DPOS server. The raw data from the collected points were processed with the base data. CORS data wasn't available, but DPOS still processed the on site vectors.
My base position for this project is still based on an autonomous (standalone) position. I calculated a simple translation from the autonomous base position to the known coordinates of my base point, POST. I then applied this translation to all post-processed rover coordinate points: L001, L002, L003, L004 and L005. I then compared the translated coordinates to my known coordinates for the monuments I tied in. The results are as follows in US Survey Feet (Base Line length in parenthesis):

L001 (69' 5 minute observation)
dN +0.0075
dE +0.0036
dU -0.0239

L002 (4825' 5 minute observation)
dN +0.0296
dE -0.0374
dU -0.0447

L003 (13560' 5 minute observation)
dN +0.0192
dE -0.0093
dU +0.0390

L004 (50102' 6 minute observation)
dN +0.0348
dE -0.0457
dU -0.0028

L005 (50102' 15 minute observation)
dN +0.0292
dE +0.0011
dU +0.0939

With comparisons like these, I would find it difficult to say that the Justin engine used by DPOS was in eerror. The coordinates I'm comparing with could be this far from "truth". I would consider these results to be statistically perfect. With this new capability, a user can locate a distant point without the concern for maintaining radio communication. This is fantastic.

There is still more work to be done before release, but these tests untold promise.
 

Shawn Billings

Shawn Billings
5PLS
This is all done entirely within the LS with Internet access. The processing is done remotely, taking advantage of more powerful processors at the server. To the user it's practically internal, no downloads to PC for post processing, no additional software.
 

Shawn Billings

Shawn Billings
5PLS
I'm not sure what the limitations are yet. I was fairly surprised to get such good results at 9.5 miles with only 6 minutes of data. We don't know if DPOS will be as robust processing points in canopy as the LS rtk engines. That will require testing. Not sure about time requirements. I started at 5 minutes but likely can go lower on short vectors. I don't know how much. All of these questions require testing which excites me considerably. This is new ground.

Another question that has my attention. Could hybrid rtk be an effective verification tool? If DPOS and the rtk agree, using different processing techniques, what is the likelihood of both arriving at the same wrong answer? If they agree, can I have more confidence in the result?
 

Joe Paulin

Well-Known Member
This sounds like it will be a very attractive tool to get the "one last shot" needed, but out of radio range. I will be very interesting to see the workflow. Will there be an option in the collect screen to collect an RTK Hybrid shot that will start static collection for that point only? Normally for RTK work I have my LS setup to not record static data for the points I collect. Fantastic work! Does other manufactures' equipment allow for this option? The equipment that I have used in the past doesn't allow for you to do this.
 

Shawn Billings

Shawn Billings
5PLS
This sounds like it will be a very attractive tool to get the "one last shot" needed, but out of radio range. I will be very interesting to see the workflow. Will there be an option in the collect screen to collect an RTK Hybrid shot that will start static collection for that point only? Normally for RTK work I have my LS setup to not record static data for the points I collect. Fantastic work! Does other manufactures' equipment allow for this option? The equipment that I have used in the past doesn't allow for you to do this.

Current implementation, which is under rapid development and subject to change, gives the user the choice to accept the raw data and whatever position is available regardless of user accuracy setting (standalone, float or fixed) or to accept the position (according to the accuracy setting) without raw data. So you have a choice. For the sake of simplicity, my vote was actually that the user be forced to always store raw data if they want to post process, but the development team has created a pretty sophisticated and easy to use process for allowing the user to make the choice.

While currently not implemented in the testing version I have, from what I understand, the user will be presented an option with a chart of which position to use: post processed from the base, post processed from CORS (imagine your base stops working for some reason, then you can process to CORS), and the standard RTK position to which you are accustomed. The vector from the base (RTK or post processed) could be from a DPOS shifted base position or the unadjusted base position. Lot's of possibilities.

To my knowledge, no system has ever allowed for integrated post-processing. Other manufacturers have required the data be downloaded to $oftware on a PC for post-processing. Then the results of the post processing must be reintegrated into the database in some way. The LS still "downloads" but it's all very painless and automated, so there is a considerable time savings. Also, the download is "virtual" so you aren't downloading to a separate device. The post-processing is fully automatic and uses Javad's servers (so the processing overhead is minimized). The results are returned to the LS and integrated into the database automatically. No additional time spent doing this manually. And all without the need for additional $oftware on the PC. This translates to an ability to perform this in the field with only the LS and the Javad base receiver. You can literally observe the rover points, return to the base, download the file (which is automatic), submit to DPOS (which is automated), and get the result back in the field. It's almost RTK in that you get a precise answer in the field from a single device without range limitations. You'll notice that points L004 and L005 above are 9.5 miles from the base. Even if I only had a 1 watt modem, I could have precisely located this point with only a few minutes of data, while being out of range of the corrections.

I think we'll be dreaming of useful applications of this feature for quite a while.
 

Shawn Billings

Shawn Billings
5PLS
I don't believe so, Nistorescu. The user has practically no options for processing, which is good (nothing to mess up). I thought I might be able to turn off tracking of all frequencies except L1 in the Triumph-LS, but I don't believe this is possible without using GRIES (something I'm hesitant to do).
 

Nate The Surveyor

Well-Known Member
OK, I have a question. Do you have to STOP and DOWNLOAD each time you use this feature? Do you then HAVE to restart the base, before continuing work? IF your base were set autonomous, then, would this not divide the base file, into a number of sessions? If this is true, then, I'm going to want a handy way to "Combine" or re-combine my base data, for DPOS, aren't I? Of course, I COULD get more manually involved.... but then it seems it might be better to use this feature on day 2, AFTER dposing the base?
I'm not real handy with seeing the FINE PRINT in the LS, for this aspect.
Thanks.
Nate
 

Matt Johnson

Well-Known Member
5PLS
Nate, the ideal workflow is that you stop the base and download the data when you are done working. Then you could process with DPOS when you get home and have the DPOS positions available for the next day.

If you really needed the Base to Rover DPOS position that day, you could stop the base, download the data, submit it and then restart the base.
 

Sean Joyce

Well-Known Member
I just viewed the website about Hybrid/RTK Automatic and how it works. This is a VERY exciting development.
I have been using this equipment since May 2014. Before that I had rented many of the latest offerings of other makes and models.
The development of the Triumph L.S./JField software and the capabilities it allows is as significant to surveying as the development of GPS in my opinion.
Can't thank Javad and the development team enough for constantly pushing the envelope.
Everything you guys do saves me time, money, and makes the work that much more enjoyable.
 
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