Looking for HOW TO for GCPs using PPK

I’m planning on getting an Emlid Reach RS and utilize CORS to establish precise coordinates for ground control points used in photogrammetry (drone surveying). I’m using GCPs because I don’t have a remote sensor setup on my drone yet. I’m new to this and I can’t seem to locate a “How To” for how you go about taking the data from the Reach taken at each of the control points and processing it with the CORS data to correct the coordinates. I don’t even know how close the CORS station needs to be. I found the Reach documentation but it appears to explain how to use it (actually use a pair of them) for RTK not PPK. My understanding, and maybe I’m misunderstanding, is that to establish absolute coordinates using PPK I don’t need two units (just one unit and data from a nearby CORS station) However I must admit it baffles me how this can happen without having at least one initial point to place the Reach on that you know the absolute coordinates already. But I think that’s just due to me still learning about PPK.

Would greatly appreciate it if someone can provide a link or otherwise throw me a bone on this. Thanks!

Hi @consultant.

We have done testing with the Emlid Reach but we were using RTK. When you use a Rover without a Basestation is when you would need to carry out PPK, hence the reason you’re asking :slight_smile:. I have done this in Trimble Pathfinder, but a lot of our customers will use Trimble Bussines center. You can download a free version of the base software on their website.

Picking a CORS station is requires some knowledge of the software you are using to carry out the post processing. This is a great article that is very worth reading regarding the topic. Here in California the ground moves fairly often so it’s important to take things into consideration. When I worked as an analyst in Colorado I frequently used stations in Wyoming and Montana.

Looping back to the Emlid. They have amazing customer support and you can usually get them on the phone if you are seriously considering purchasing a unit. Please let me know if you have any other questions moving forward.