I am a geologist working with off the shelf UAVs (at present DJI P3 and P4) to build photorealistic models of cliffs using Photogrammetry (Photoscan by Agisoft). At present we find that the models are precise but not accurate. One way to fix this is to place ground control points (GCPs) in the model which are surveyed using DGPS. All of the DGPS solutions I am looking at are very expensive (c. £10k) and are also too bulky for us.
I am wondering if anyone has some advice on budget DGPS that will give decimeter accuracy, using two receivers. This does not need to the real time but it does need to be robust, reliable and at a scale that is similiar to a handheld GPS.
Also I do not have the time/skill to build something and write code, I need to be able to buy something that works. The budget for a full working system would be around $1000.
At the moment it seems like there are handheld, civilian GPS that gives accuracy of 1-5 m cost $100 or there is the full survey kit, RTK etc with sub-cm accuracy that costs $10k and nothing in between.
Any advice gratefully received
Our Thanks for the quick reply. Yes - thats how I ended up here, the ReachRTK came up in searches
What I see when I look at the images and specs is two receivers and a couple of circuit boards. How would I get that as something I could give to a geology student (zero electronics and fairly clumsy), so they could carry it to the field, set one up as base station, the second one as a rover and then store and download the data and then get it processed.
I understand that you build the components, is there anyone who can create the equipment we need from those components
Thanks
John
Read the docs to get an impression of the system.
You will basicly need the reach kit, 2 USB power banks and a smartphone to get the system running.
To get the coordinates you need to postprocess the logs with rtklib.
It is not as easy and fail save as a e.g. Trimble rtk system but it is less expensive. If time and possible fails don’t matter reach is the right system. If time and fails matter you would spend the money for a e.g, Trimble rtk system.
Thanks Tobias, I’ll take a look now
@John_Howell, As @tobias-dahms said, you basically need the Reach Kit, USB power banks and a smartphone (or laptop, or tablet). Some kind of tri-pod or rod, with a bubble level (or plumb bob) to set them up directly over your points would be nice too. I would also like to add that it IS easy and fail safe. I have personally used Trimble RTK Systems since 1997 and have only been using the reach for a few months. The reach does everything the Trimble can do, from a coordinate and accuracy standpoint… so long as your baseline distances are less than a few miles. If your baselines are longer than that, the REACH accuracy drops off as the baselines get over 10km. But, you can get decimeter accuracy many miles away. I haven’t tested the limits, but I’m pretty sure that you will for at least 10-20 mile long baselines.
The easiest way to use the REACH, in my opinion, is to post-process the results for setting GCP’s. You can do this with RTKLIB, which is free software. Here is a link to the EMLID DOCS which tell you exactly how you do it and what settings to use, step-by-step: https://docs.emlid.com/reach/gps-post-processing/
The only thing you have to change in these steps is from Kinematic to Static (for “Positioning Mode”), since you aren’t putting it on a moving vehicle and only processing ground control. If you take a little time to get your REACH setup in RTK (which isn’t very hard and documented very well), then you could get coordinates on your points with much less observation times.
If you have any questions with the setup or operating issues, just post something to these forums and you’ll have an answer very quickly. Typically @igor.vereninov will answer it within hours 
Good luck and enjoy using the REACH! I know that I have!
-Steve
(p.s. I am in no way affiliated with REACH or EMLID, just a surveyor and UAV user in the US always pushing the technology envelope…)
Hi…i am a new user here. As per my knowledge it is not as easy and fail save as a e.g. Trimble rtk system but it is less expensive. If time and possible fails don’t matter reach is the right system. If time and fails matter you would spend the money for a e.g, Trimble rtk system.