CORS Corrections to Base and Base Corrections to Rover


I’m planning out my first UAS imagery mission with the Reach and would appreciate it if someone reviewed my plan. I have 2 Reach RS2 units, external LoRa antenna, a tripod and survey stick. Basically, the plan is the following:

Setup Base station and have it receive corrections from CORS through a cellular hotspot on a phone.
-The CORS station is about 20 km away from where I plan to put the Base.

The Rover will be used to get locations of GCP tiles I’ll place around the area to be GCP and Check points in my photogrammetry software.

In looking over the documentation, watching Youtube videos and reading form posts, I have a few questions on this plan:

    • Will getting CORS data do much for me if I have a good base placement with a good signal lock and some time to stabilize? Is linking my base to a CORS station 20km away worth it?
    • Should I capture known points from USGS? There are a couple around but they are pretty far away. There are a few vertical control points about 5km away from the area and a couple Classic Horz and Approx Ht points a few km away. I could capture them but again, would they add much value?
  1. I have read that the CORS corrections only need to be averaged by the base for 10 minutes then can be disabled. Is there benefit to having a continuous CORS link to my base over a day or two?
  2. Can you receive CORS corrections from the internet over WiFi and send corrected corrections over LoRa to your rover at the same time?

My end goal is to create 2D and 3D maps of the area to show within a few inches of ground truth when you are in the area and not be 6-10 feet translated west or something like that. The UAS can easily get 2-3 cm GSD.

Again, I’ve done a fair bit of reading and in these areas, I could use some specific advice.

Thanks again!

Congrats on the startup! If you have a base, rover and known benchmark relative to the subject then you don’t need CORS at all. If the benchmark nor CORS are relative to the subject then you can use the CORS to get a point on the base that you can manually enter in the future. What I mean by relative to the subject/site is that depending on the use the site may have had control carried in by a surveyor that would have surface coordinates and elevations that may not be related to WGS84 datum. This is a typical scenario for development and construction in the United States. In addition to that there might be a site localization which you can search the forum for more information. A check-in benchmark is always a good thing as long as it is on the same datum you are using for the GCP’s.

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Hey there,

You did a great job on reading the materials! Your plan sounds good.

Michael has already provided a valuable input, I’ll add mine to answer the particular questions.

If you have a good survey mark on site, there’s no need in using CORS continuously. Although, I’d use it once to double check the survey mark is accurate.

You might want to capture them just to check yourself and make sure that the data you collect with rover is accurate.

There’s no benefit in having a continuous CORS link. Once base is set up, you can disable it.

Yes, you can, however, this is not required for your workflow.

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