GPS speed error - pre arm

ArduCopter
1

Hi,
i’m running 3.5.6 RC10 with mrobotics X2.1 and gps mRo uGPS ublox SAM M8Q.

I have problem with pre-arm checks. many times it shows “gps speed error” and i m not able to arm.
I checked and usually the gps see 14-16 satellites with HDOP below 1 (0.5 - 0.8) . the problem is probably the VDOP which seems to be 1.1 or 1.2.
How can i fix it? there is a parameter to increase the tollerance?
or the problem could be somewhere else?

2

hi guys, someone can help me?

3

Gps Speed error means err… gps speed error. The FC sees that according the GPS the copter is moving, but it should be steady before arm.
It could be noise from your plane, or indicating the fact that the teeny-whiny antenna on the M8Q is not the best solution for navigation purposes.
At the end it indicates gps problems. Try waiting a little more (couple minutes) if it not goes away, relocate the gps, or eventually change to a gps with larger antenna.

4

Thanks for your reply.

there is no way to increase the tollerance in VDOP ? or in gps speed?
sometimes FC says wants to be <1 and the detected speed is 1 or 1.1 so i’m very close to threshold.
thanls

5

it is governed by the EK2_CHECK_SCALE or EK3_CHECK_SCALE, depends on which EKF are you using. Values greater than 100 increase and values less than 100 reduce the maximum GPS error the EKF will accept. A value of 200 will double the allowable GPS error.

BUT, if there are horizontal speed errors and they are not intermittent, then you could experience strange behaviors in loiter or other gps assisted mode. Be prepared to switch back to AltHold and take over control…

6

I will carefully try to increase and let you know!
thanks!

7

Marking this information. Thanks.