Question regarding RTK and PPK in densely forested area without internet or known coordinates

Hello all,

I have a question regarding using my RTK drone to do oblique mapping of forested plots in an area where I cannot receive corrections.

My workflow is:

  • Set up 1 emlid reach RS2 in open-sky to log its position for 6+ hours

-Travel to my sites (1-10km away) and collect drone imagery using a Mavic 3E with the RTK module.

-Use PPP to correct the base stations position, then PPK the resulting drone imagery with the updated base station position.

My question is,

I have a second emlid reach RS2 available, would it be worth it to bring it with me to the plots and set up on an unknown point to send RTK corrections to the drone?

Or just fly the drone with the RTK module without setting up another reach unit at my plot locations?

I am wondering if it may affect the PPK process if the drone images were corrected with an RTK from an unknown point during the flight, even if I process them using the known base station position later?

Thank you all for any insights into this!

I should add that I have to align the photogrammetry point cloud with a terrestrial LiDAR point cloud over each of the plots so absolute accuracy is a must. And I wont have any way to receive corrections at the plots themselves.

You can do a couple things with your second RS2!

  1. Use it to collect ground control points which you should do for drone collection anyway because it will give you actual accurate positions on the ground. Use the first base station to correct the log of the second base station. But MAKE SURE you set the corrected position in Emlid Flow!

  2. Use it as a base station transmitting RTK corrections to the drone. Then when you do your postprocessing, use the log from the first base station to correct the location of the second base station. Then make sure you use that position when you use the second base station log to correct the drone log.

1 Like

Hi @bengwill,

I agree with @daygeckoart! You can use the other RS2 to collect GCPs. Since you don’t know the precise position of the base yet, you can do any of the following:

  1. Collect the ground control points with the other RS2, and post-process it with Stop&Go. For this, you need to record the raw data logs from your base and rover, along with the CSV file for your measurements.
  2. Set up the 2 Reach receivers as base and rover, and set up the base in Average Single. Take note of the averaged position of the base. Once the precise coordinates of the base are known with PPP, you can manually adjust the position of the GCPs based on the difference between the old and updated coordinates of the base. More info about this workflow can be found here.