Using 3 or 4 Reach GPS Units as Compass, IMU, etc

Hi there, I’m new to the RTK game and still finding my way around the REACH modules, but I was wondering if anyone has tried or knows a way that can allow us to use 3 or 4 gps units to measure:

  1. Yaw
  2. Pitch
  3. Roll
  4. Acceleration

Instead of using magnetometers, accelerometers, etc…


You know Reach has a built-in IMU, right? Regardless, I don’t think it would take a lot to bring in the position log from three Reach units and process their relative positions into vectors. Acceleration of pitch, roll, and yaw, sure, but if you want acceleration of the vehicle relative to the earth, then you need a fourth GPS as a fixed base station on the ground somewhere.

So, are we talking about a large vehicle like a sea-going ship or something small like a drone?

Great, thanks Bide. I’m thinking of trying to use this on a 1000mm hexacopter. I fly in some harsh high RF environments which usually knocks out the compass of the IMU. With gps antennas, this would help to fly in these environments without risking an IMU malfunction.

It’s interesting, I’m just thinking how to implement this with a Navio2/RasPi2 board. Will need alot of coding I think.


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That is an interesting idea for sure. It makes you wonder how far apart the Reach units would need to be from each other for a reliable result, and yes a lot of coding to process the data quickly enough for your hexacopter. Quite a challenge!

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I see many issues with such an idea, the biggest being dynamic available. With a 5Hz setting, needed for me to use both GPS and GLONASS, you are able to achieve just 5Hz dynamic, which is quite low for efficient stabilization

Thats true Michele! I wonder what the minimum update rate would need to be for efficient stabilisation? Maybe just using 2 gps units for heading information and still use the IMU (except compass). Actually maybe 5Hz would be enough as we’re only talking about slow, sluggish flying anyway.

Do you know anyone that has implemented dual reach GPS units for heading in Navio/Arducopter?

All dynamics is handled by gyros, compass is only used to provide absolute reference (north direction) and to cancel the integration error. Same thing could be done with RTK heading, so 5Hz should be enough.

Heading output with dual Reach modules is something that we have on our roadmap.

I am working on such integration as well, just fighting with free time that’s always not enough! The solution I’m looking at is the same - Kalman filtering of 9axis using the 5hz ‘real’ heading as the most important correction factor. i.e., 100/200 hz dynamics from the 9250 and a 5Hz ‘check’ when we have a true fix. I already took many tests with two reach and RTKLIB and I’ve to say I’m really pleased with them, as long as you have good GPS signal