Hello,
We are working with the Phantom 4 RTK and DRTK base station, and using the Trimble Catalyst to get check points.?ÿ We set the DRTK station over a known control point, but are running into some issues.
The Trimble Catalyst can only provide points in ITRF2014 with the GRS80 model.?ÿ This is fine, as the drone natively captures in WGS84.?ÿ Our problem is when we start trying to work with engineers who are using NAD83CSRS with?ÿCGVD2013.
Our current workflow includes Pix4D and Virtual Surveyor, but we need a way to be able to provide this data to the engineers in the modern Canadian datum.?ÿ Neither of these allow for the ability to output elevation in the HTv2.0 geoid model.?ÿ Pix4D does allow for an offest on output as Height Above Ellipsoid, but in reality this number would change over the any project site.
Has anyone found a way to work through this??ÿ Or have a workflow that works for them?
Any help would be greatly appreciated!
Has anyone found a way to work through this??ÿ Or have a workflow that works for them?
Yes....
Set your Trimble GNSS to collect static data at 1 second epoch rate. Then post-process the DJI P4RTK Rinex data provided by the drone.?ÿ You can use a GEIOD this way, and you should see better accuracy than RTK.?ÿ
Is the known control point that you set up on in WGS84 or the NAD83 CSRS coordinate system? Before you layout targets for checkpoints, are you checking into this or another known control point relevant to the worksite??ÿ
I may be wrong because I haven't used CGVD2013 but the HTv2.0 geoid model is based on CGVD28 and I think there are differences. You mention both in your post. Agisoft has Canadian Geoids, I have no idea why PIX4D can't/won't add more to their library.
@leegreen Thanks for your insight; so I should be processing the Rinex data with something like Propeller or KlauPPK??ÿ Thanks!
Thanks @mjs! Our known control point is in WGS84.?ÿ It's frustrating that you cannot add geoid models from NRCan into Pix4D, and it doesn't seem like this is a feature they're planning on adding anytime soon!?ÿ I believe there is about a 0.4m elevation difference between models - a lot of local surveyors are still working in the outdated datum as both are still accepted.
Hello,
We are working with the Phantom 4 RTK and DRTK base station, and using the Trimble Catalyst to get check points.?ÿ We set the DRTK station over a known control point, but are running into some issues.
The Trimble Catalyst can only provide points in ITRF2014 with the GRS80 model.?ÿ This is fine, as the drone natively captures in WGS84.?ÿ Our problem is when we start trying to work with engineers who are using NAD83CSRS with?ÿCGVD2013.
Our current workflow includes Pix4D and Virtual Surveyor, but we need a way to be able to provide this data to the engineers in the modern Canadian datum.?ÿ Neither of these allow for the ability to output elevation in the HTv2.0 geoid model.?ÿ Pix4D does allow for an offest on output as Height Above Ellipsoid, but in reality this number would change over the any project site.
Has anyone found a way to work through this??ÿ Or have a workflow that works for them?
Any help would be greatly appreciated!
In case you haven't found these, NRCAN provides these tools that should be of use:
No. Not limited to those specific drone apps. Can use any Static post processing program like TBC or Magnet Tools.
Under the GNSS configuration > Detection mode> select from list. I was able to change the projection and geoid. "NAD83 (2011)" checked in beter with the RTK units rather that the 6 other NAD83 options on the list.
It doesn't have HT2_0 on the list of geiods though, just CGVD2013A.
?ÿ
Does it mention CGVD28? HT2_0 is derived from this but with some revisions in the late 1990's and 2000's.
@mjs I'll have to check when i get one of the android devices back in my hands. I sent them all out to a job site. We are currently using them for horizontal only but, having the the correct geiod would be great for future projects. Thanks for the info.
@jacob-wall thank you! We found that placing the DRTK over a known point, fly the site, process the data, and before bringing points into Civil 3D, we run it through the GPS-H tool and we are right where we need to be - a "good enough" solution for now until Pix4D will start offering Canadian geoid models.
@mjs In the Trimble Catalyst Manager app you can choose from CGG2013A and HT2_0
If using the UAV Ground Control app, you are limited to only ITRF2014 with GRS80. Our Cansel sales rep mentioned that Trimble PenMap is another subscription based app that may have better point averaging solutions, integrates fieldwork with TBC, and can select a few different geoid flavours... I haven't been able to give it a try, but just another option.
