gcp (1)

Hello DIY’ers!

I stumbled upon this 2015 post from Gerard Toonstra and am looking to build a similar setup:


There’s a ton of useful information in his post/blog, but since several of the links have now aged and technology has advanced, I thought I’d create a new thread on the topic.

I have a Phantom 4 Pro which I have a few years of surveying experience with (I’m not a licensed surveyor) doing aerial mapping and using Pix4D, so that part's covered. What I don’t have is $30k for an RTK unit lol.

I'm looking to build five small GPS "boxes" to place on my GCPs in order to increase the relative accuracy of my maps in all three axes. After a few days of research, I have a better understanding of how to build said boxes, but not enough to pull the trigger on the required components yet. Here’s where I’m at:


  • Accuracy:   Relative accuracy is more important than absolute accuracy in my case, at least for now. I’m shooting for sub-20cm accuracy after letting them log for 1-2 hours and processing using PPK. Getting down to sub-10cm without needing a base would be awesome, but I’m not sure that’s realistic.
  • Arduino+Shields vs. Raspberry Pi 4:   I don’t have any experience with either option. I plan on getting familiar with one or the other so I can build these boxes now as well as a mapping UAV in the future. It seems Arduino+Shields is the simpler and cheaper route, but I like how the Raspberry Pi 4 comes with so much capability packed right on the original board. I’d happily pay the extra money for the Pi if it makes sense for this project. If I go with the Pi 4, is 2gb enough memory or should I go with the 4gb version?
  • GPS Module:   Although the ZED-F9P claims to be around 1cm accuracy with RTK, it seems a bit overkill if using it for static logging and PPK. As for cheaper GPS modules I'm looking at the M8N or M8T, unless there's another capable/cost-effective module that I'm unaware of.
  • Usability/IO:   I'd like to be able to have my settings saved for the boxes instead of configuring them before each job/flight (EEPROM?) so that I just flip a switch and they eventually start recording until I turn them off. A few LEDs (or mini LCD screen) to indicate battery charge and satellite fix/data activity.
  • Runtime:   Battery operated, rechargeable. If I had to let them collect for let’s say four hours would one or two 18650s do the trick? AAA’s? I’ll likely be logging at 1Hz.
  • Communication:   Do I need antennas for them if they’re not communicating to one-another?
  • Data Storage:   Stored onboard each of the boxes. I assume via SD cards.
  • Programming:   I have a little coding experience, I’m sure I can learn what’s required.
  • Enclosures:   I’ll model and 3d print them.
  • Random unknowns:   Data Logger (Arduino + Sparkfun Logomatic v2? Do Raspberry Pi’s already come with data logging capabilities?), Software (u-Center looks nifty, not sure if that’s needed for PPK though), Data Processing (RTKLIB? RCTM?).
  • Budget:   A few thousand USD, I realize that generally speaking higher accuracy = more money.
  • Working Location:   NW United States.

I know this is an absolute mountain of questions, many of which are subjective, so any spattering of info would be greatly appreciated! I’ll be sure to share my build-in-progress and performance of the boxes here in case others find it useful. Thanks!

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