HERE GPS, Bad GPS Health

Here GPS
21

Are there any recommended PDOP values? I did some tests outside to compare the HDOP and PDOP values. When I had HDOP values of around 1.4 (the default in ArduCopter) I got PDOP values around 2.5-3. I set it to 3 currently.

Also are you goint to address this issue in a future release of AC, or just simply mention it in the documentation about setting up the here2 gnss module with CAN?

22

newer models will address this

23

Unfortunately adjusting the GPS_HDOP_GOOD parameter doesn´t quite solve the problem. For some reason Ardupilot doesn´t allow to arm above a value of 2.5, even though GPS_HDOP_GOOD is set to 300 or 400. The EKF letters in MissionPlanner is also red with no position estimate if HDOP is above 2.5.

Is there any solution for this besides completely disabling the GPS checks, which I would like to avoid?

24

i think i might need more info. have you updated the firmware on your here 2?
as there are alot of people using this without any issue

25

I have not changed the firmware on the here2, nor have I altered the configuration of the M8N module. Yesterday I was trying to take off from an altitude of ~2400m MSL with a clear view towards the sky and nothing around for miles, but I got an error something like gps hdop needs to be below 2.5 to arm, even though the GPS_HDOP_GOOD was set to 400. The HDOP value reported was around 2.7, which is quite strange since in the valley I get values around 1.6-2, even with some obstacles towards the sky.

Is the firmware of the here2 open source, can we alter it to report hdop instead of pdop? Or do you think, that a firmware update according to this would solve the problem? I could not find any information/changelog about the firmware of here2.

26

I have never seen this error with CAN and I’ve used it a lot. Yes HDOP did not reporting but Iv never been told can’t arm because of it

What firmware version you using on your autopilot. .

27

I am using copter V4.0.3.

28

Ok, I have found the problem:

In copter 4.0.3 libraries\AP_NavEKF2\AP_NavEKF2_VehicleStatus.cpp line 189:

// fail if satellite geometry is poor
bool hdopFail = (gps.get_hdop() > 250)  && (frontend->_gpsCheck & MASK_GPS_HDOP);

This should not be hardcoded but instead the GPS_HDOP_GOOD parameter used…

29

I have the same issue, using m8n 3.01 firmware, Using black cube, gps connect serial port, 3dfix over 15 sats, hdop < 0.5, will show bad gps health