DIY RTK GPS Drone Build | Just as good as IR-Lock and Vision Landing?

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Hey everyone! Caleb here.

Just thought I’d share a recent project I’ve been working on. My DIY Drone interests has been pretty much captured by RTK + ArduPilot as of late.

I upgraded a Pixhawk 2.4.8 F450 build with an RTK GPS, namely, the ArduSimple board. Had to use their lightweight antenna to get away with RTK on a drone. This one only weighs 78g!

I have previously conducted precision landing with arucos and vision, but I wanted to test the ability of precision landing with just raw RTK GPS alone.

In the video, I run a simple AUTO mission: fly to a waypoint and return to launch. I manually arm the drone each run, fly it in to the air, and only then hit AUTO mode so that I can place the drone back in the marked waypoint every trial.

This test was done for both the popular non-RTK GPS chip, M8N, and the RTK upgraded F9P. Each setup had 8 runs to get a good average.

I go into further detail in the video, but the takeway is this:

The M8N GPS landed distanced averaged about 52" away from the home waypoint, the RTK GPS landed distanced averaged about 16" away from the home waypoint.

First asterisk on the RTK GPS RTL mission: I had 3 bad lands in a row and I wasn’t monitoring if I had RTK fixed up. Pretty likely it was dropped during these lands since the other 5 were dead accurate. I also had a pretty tight WPNAV_RAD parameter at 10cm and I think this may have aborted the RTL land- since many of my RTLs had the drone hovering over the home waypoint for 2+ minutes. I increased this to 20cm and the problem dead-accurate landing was there.

Second asterisk: I did not tune the drone, and was using stock PIDs for an X-frame. Definitely needed a tune, as I drastically changed the center of mass with my setup.

If you take away those 3 bad lands that I am 95% are due to dropped RTK fixed or too tight of a WPNAV_Radius, the average land is only 8" away from the home waypoint.

With a proper tune, I bet the average landing distance goes down even further.

That’s starting to flirt with conventional precision landing methods in my experience.

Anyways, I go into much more detail in the video, so check that out here

Would love to hear what you all have to say!
–Caleb Bergquist

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My Here3+ equipped copters usually land within about 3” of the intended spot with a good RTK Fixed solution. Precision would likely be even better using a Zed F9P based module.

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From experience with Precland, in around 80-90% of landing, GNSS with or without RTK (depending the unit, tuning, etc.), will do fine. If you want the latest 10%, you need another system (vision, beacon, etc.).

But nice post, that is really interesting !

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Flying drone light shows with a L1 system, I have had 500 drones (450ish size) take off and land on a 18x18 square of plastic on a beach.

What is your sky visibility and what are you using for a base and antenna combo…I am assuming ardusimple for the RTK Base.
Is the base level.
Do you have a Fix or Float
Have you let it sit for a few min before collecting location for base. L2 is quicker because it can see more Sats…it still needs to see a few before you can get your FIX.

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yeah here3 or 3+ is based on ublox m8p,is 8th product,I try to use m9n,is can land within about 20 cm,then i use f9p and auto config,The accuracy can reach 5 cm，You can also do nothing while hovering，have’t any move you can see

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No one is arguing that the M8P is a great choice or more capable than the F9P.

For basic RTK operation, it is likely adequate. That’s all.

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you are right,i try to use m8p,in the same place m8p need more time to fix or almost can’t rtk fix,however in this area f9p usually use 30s-1min enough to rtk fix，The horizontal contrast gap is obvious,by the way，i use 2 f9p one for base ,one for moving base,and the base initialize（2.5m，60s）,About 5 minutes

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It looks very impressive with rtk hahah（Excuse my poor English）