I’ll be starting drone mapping work soon as part of salt marsh monitoring on the US Atlantic Coast. I’ll be purchasing 2 Reach RS2’s for shooting ground control points and will be flying RTK missions with the DJI P4RTK and D-RTK2 base station.
Our project’s budget doesn’t allow for an NTRIP subscription and we will most likely be working in areas with low cell reception anyway, so I’m planning on using a PPK workflow with the RS2s to get my ground control points, that will bring the P4RTK’s data to an absolute accuracy. As I’m a total noob at this work, I just wanted to check with the community to gauge my understanding of the workflow:
In situations where I will have a CORS station nearby and no on-site benchmark (most of the work will be done within 10km of nearest CORS station:
- Set up physical ground control points around study area.
- Using one RS2 unit as a rover, collect single solution points for each GCP. My understanding is each point will take about 5 minutes to collect a reliable Fix position.
- Post-process GCP data using RTKLIB, using the RS2 logs as rover and the nearby CORS station logs as my base station.
- Fly RTK drone mission using P4RTK and D-RTK2 base station.
- Offset point clouds to my absolute-accurate GCPs using Pix4D. (I’m planning on using Aerotas’ workflow for the P4RTK and D-RTK2 base station.)
In situations where I will be ~30km from the nearest CORS station and will not have an on-site benchmark
- Set up one RS2 base station at an unknown point, starting logging static data for ~4 hours.
- While the base is logging data, set up my physical ground control points and use the second RS2 as a rover connected to the base station to shoot GCPs.
- Turn off base station after logging is finished and pack up.
- Obtain base’s absolute position either using OPUS or PPP.
- Offset collected GCP data to match the new corrected base position. I’ve seen a few different methods of doing this but if someone has a favorite/reliable method please feel free to share.
- Fly RTK mission using P4RTK and base station, and offset drone data to GCP data in Pix4D.
I didn’t include the endless amount of technical nuance involved in each of these steps, but I just wanted to make sure I’m on the right track generally. I’d like to identify if there are any gaping holes in my strategy or general tips to improve efficiency. If you’ve read all of this, thank you very much and I encourage brutal honesty in your feedback.