Altitude accuracy
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What is the expected accuracy of altitude estimation in PX4? With a good satellite connection (19-20 satellites and HDOP of 0.6-0.7) and the addition of a range finder should I expect the altitude estimates from PX4 to be accurate/steady? If yes, is there any suggestions for achieving a good altitude estimate?
With the VOXL m500, I am seeing altitude measurements that are often off by 1-2 meters, and fluctuate up to 1.5 meters in both the up and down directions. The only way I have achieved a reliable altitude estimation is the set EKF2_HGT_MODE to use a rangefinder. However flying in this way is undesirable for my work. If EKF2_HGT_MODE is set to barometer or GPS, the altitude fluctuates significantly, causing vertical deviations in position mode. This occurs with EKF2_RNG_AID enabled and disabled.
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@blakekrpec I think HGT_MDE needs to be Baro "and" GPS.
The EKF does a fusion estimate there to put it simply... ,) -
I only see discrete options for baro, GPS, range finder, and vision as possible values for the parameter EKF2_HGT_MODE. These are defined in the PX4 docs here
My understanding is that the PX4 EKF requires the definition of a primary altitude sensor (via EKF2_HGT_MODE) and then all additional altitude data is fused to estimate altitude, but that PX4 does not support the definition of multiple primary altitude sensors.
If this is incorrect and you are aware of a parameter to enable this behavior I would be happy to try it out!
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@blakekrpec As I understand the ECL/EKF library integration so far, you can run several instances that each will fuse different sensor combinations (with individual blending) to accommodate for estimation state errors and the like....
