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Altitude testing of beta-5

I am doing some testing with the beta 5 and altitude, using gps as the primary source for alt and also using gps for yaw, so that forces me to use EKF3.


From comparing Ctun-Alt e GPS-Alt, the gps alt has more stability and I couldn’t figure out what was causing the oscillation in Ctun-alt

Is there a way to disable barometer through code modification? I want to test what the ekf would show if only the gps was enabled.

Sorry if a missed a concept, but: Is possible to use GPS for yaw with a single GPS ?

GPS for yaw requires two GPS modules.

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Any idea how much difference is there between using GPS for yaw using 2 GPS and using GSF for yaw with 1 GPS ?

oh I use two gps, but I only use one serial input

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I dont think you can use with just one gps, I use two, I just use only one serial input


I don’t think anybody has done comparisons yet of GPS-for-yaw vs GSF but I would expect GPS-for-yaw to do a better value as long as the GPSs are reporting good positions.


So here is a graph of what I think you’re looking at. So this is the GPS alt vs the EKF alt (I’ve graphed POS.Alt because this version of the EKF alt is expressed as the alt-above-sea-level).

So you’re seeing oscillations of about 12cm or so that we don’t see in the GPS. I’ll ask @priseborough if he has any idea. The altitude should be simiply coming from the accelerometers + GPS.

thank you for looking into this

Gotcha, I’m really down to test GSF feature in this week, i need just one help, I get it that GSF feature will automatically takes over compass for yaw measurement when compass becomes unhealthy or start getting high compass variance (XKF4.SM), but I don’t know how high compass variance we are talking about before GSF comes into picture ? Is it when compass variance crosses FS_EKF_THRESH value ?

If yes, then I like to fiddle with that condition, I want GSF takes over compass much earlier like when compass variance will be more than 0.3 for more than 3 seconds, can you please help me where in AP_NavEKF or AP_NavEKF3 this condition for switching to GSF is getting checked ?

Hi @Notorious7,

Re GSF taking over more quickly, I actually don’t know where the code is that it uses to make the decision but I think it requires 3 of the 5 mini EKFs to agree on the heading within some threshold but then it also has a hardcoded minimum time I think of a couple of seconds. Those thresholds will all be within AP_NavEKF3 somewhere but I don’t know where. The FS_EKF_THRESH is only used for the EKF failsafe which is really more “vehicle” code so this particular parameter is not involved.

Hello, have you discovered anything @rmackay9 ?

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