I’m using here+ RTK setup for my octa-copter along with GPS blending using two Here3 GPS modules as the rover in the setup. In RTL mode the octa landed near the base of the RTK and not at the place from where it was launched.
Any help would be appreciated.
Update to ArduCopter 4.2.1-rc1 and make sure you get a good gps signal before taking off
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Hello @Mayuri
Be sure that you are flying with your GPS status showing RTK Float or RTK Fix, and be sure that you are using a nice accuracy for the survey-in procedure of your RTK base.
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I had a similar experience when we first started using RTK; my expectation was the RTL position would be more accurate than it was. Reducing the EKF GPS noise measurement parameters, like EK3_POSNE_M_NSE, improved the RTL accuracy. I think that reducing the parameter causes the EKF to trust the GPS more which is warranted when using RTK.
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To which number did you reduce the value?
I set it to the minimum of the recommended range, 0.1, and didn’t observe any issues.
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First step is to update to the latest 4.3 stable firmware. Then ensure the fix type is RTK Fixed. RTK Float is better than a simple 3D fix, but only by some margin. Unfortunately, many of the less expensive RTK modules do not maintain an RTK Fixed solution very well, especially on a moving vehicle. Filter settings may help, but it’s consistent fix precision that is the primary driver.
Fixed base proximity is also a factor. If it is more than ~20km away, accuracy and precision will suffer.
Remember, as well, that geographic accuracy is always relative to the fixed base surveyed position, while precision (and thus repeatability) relies upon the fix state.
My copters equipped with Here3 RTK modules and a fixed base nearly collocated with the landing site almost always land well within 30cm of the takeoff location. EKF and nav parameters are all default on them.