Unhealthy RTK-DUAL-C module from Taiwan LOCOSYS

ArduCopter Traditional Helicopter
1

Hi everyone
I use RTK-DUAL-C module from Taiwan LOCOSYS
Can work well when used on GPS FOR YAW
Can also work normally at 5HZ
But the Mission planner message still generates GPS unhealthy（Unhealthy GPS signal)
I checked many articles without the correct solution. Is there anyone who can help troubleshoot the exception?

Attached is a simple mission flight LOG

2

Hi Wade!

I don’t know the specific details of your GPS-unit(s), but I have an idea, where your problem might come from.

I looked at your logs and the GPS accuracy is actually very good. You have an HDOP value of 0.48 or lower at all times. So, it seems that your GPS is not actually bad. But when I look at the map in your log, I can only see two lines, which means, you’re not using GPS blending. As the reported accuracy is always the same for both units, I’d assume, that ArduPilot can’t decide which one to choose. So, it’s always switching back and forth between the two which results in a jumping GPS position and your warning message.

What value have you set for GPS_AUTO_SWITCH? If it’s on 1 (UseBest) that might be the problem. Try setting it to 2 (Blend) or if you don’t like that for a reason to 0 (Use Primary).

You can find more information on GPS blending here:

https://ardupilot.org/copter/docs/common-gps-blending.html

3

ARMING_CHECK,1

Try setting GPS_GNSS_MODE and GPS_GNSS_MODE2 to 5 or 65 - whichever works best for you.

Are these set accurately?

GPS_POS1_X
GPS_POS1_Y
GPS_POS1_Z
GPS_POS2_X
GPS_POS2_Y
GPS_POS2_Z

I didnt see anything wrong in that log, but I could probably miss it easily since I am not very experienced with RTK or GPS for Yaw.

4

Hi Wade,
I’m experiencing the same unhealthy GPS problem on the RTK-DUAL-C module . Have you managed to identify the cause behind this issue?

5

The original manufacturer is currently asking the manufacturer to clarify the problem, but this abnormal warning does not seem to have much impact on flight.

1 Like
6

Thanks for your quick response.

7

Hi,
It looks like the LOCOSYS RTK_DUAL module is not “completely” compatible with F9P.
Just found a patch branch here:GitHub - rliou2000/ardupilot: ArduPlane, ArduCopter, ArduRover source
Two files, AP_GPS_UBLOX.h and AP_GPS_UBLOX.cpp need this patch in order to support RTK_DUAL modules.

I have no chance to test the patch yet.

8

Because UBLOX uses L1+L2
RTK DUAL uses L1+L5
I used to think they were universal

9

Both GNSS chips inside the RTK_DUAL module uses L1+L5. So there is no problems for relative position calculation. For RTK positions, the connected base station must support L1+L5.