Hi again ,

I am still having problem in Auto modes using Pixhack FC

My Question is

What's the different between ( Absolute , Relative , Terrain ) Altitude in Mission planner ?

Whats is the function of the check box ( verify Height ) ?

also in the right side under Home Location there are

Lat : -------------

Long : ------------

Alt (abs ) :-----------

Dose Alt (abs ) effect the flight altitude ?

Why always altitude keep drop in auto mode ?

this is my screen captured for the mission planner  , flight plane Tab

dose there any problem in my MP version,?

hope I can figure out any useful information ,,

regards ..

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Just fly it and see if it's reporting 60m altitude when it appears 60m high. See if it reports 10m when it appears 10m high.

The fuse vent was just a thought. Flowing air can create vacuums or can create stagnaton pressures that I've always thought could mess with barometers snice they are so sensitive. I've never had an issue, but it's a possibility I guess. Otherwise I'm kinda out of thoughts unless your waypoints are just being input incorrectly.

thankx James ,

I will try that test in next fly ,

Dose there any way to test all sensors in the ground ? 

just like simulation ( I couldn't connect the FlightGear to Mission planner until know )

regards ,

I don't know of a way to click a button and test everything.  You can test each one individually for proper response to an input though, depending on what they are.

For instance, a barometer reacts to air pressure.  You can set a GPS home point, then drive up or down a big hill and see if it responds appropriately.

The issue I brought up is a dynamic test that requires airflow over your fuselage to really test how the airflow is affecting air pressure in your fuselage.  The only thought I have there is to strap the fuselage to the outside of your car and go for a drive.  It seems like a good way to damage your fuselage though.

nice way ,

 The Car roof alt about 2 meter, Is it enough for Auto mode to work in speed about 60 kph ?

what about simulation flight gear dose it simulate all sensor ?

kindly visit this link

Mission planner simulation with FlightGear for ( Plane ) fails.

all regards ,


I am looking for some answers regarding altitude in mission planner.

1. What does the 'altasl' (file attached) value stand for? is it the altitude of GPS only or does it represent Barometer only or mix of both?

2. Where in mission planner (telemetry file) can I find altitude calculated from:

    i. GPS only

    ii. Barometer only

I am using Pixhawk with 3.4.0 arduplane and misson planner 1.3.34.

Please help me out understand and find the info I'm looking for.



That altitude is a list of where APM thinks it is.  It mixes this value from the baro and GPS based on the following parameter.  So - barometer - unless you've messed with this parameter.


I'm not sure where to find live raw GPS altitude data.  Might be able to read it in the log files.

ALT_MIX is default i.e 1 so this is showing 100% barometer,

Does the mission planner show GPS alt under the status tab?

I know I'll have dig into the dataflash log to find GPS alt, but playing back a telemetry log is easier in the mission planner GUI.

I had a similar problem with a flying wing with the pixhawk built into the wing, I solved it by making a 3/16 hole through the wing near the pixhawk to allow the pressure to average between the top of the wing and the bottom of the wing. works great. 

so what the value "alt" indicate under the status tab?

I believe that is alt AGL, but I don't recall 100%.

Thanks, but that I know. What I meant to ask is that is this gps or baro reading, because "altasl" (100% baro) changes too much (1-9m) while on ground and alt reading remains almost same, very slight change (0.01- 0.10m) .

Being that the barometer reading should be much more stable than the GPS altitude reading, it would lead me to believe that the stable one (ALT) is based on the barometer (or maybe mixed based on the parameter) and the jumpy one (altASL) would be GPS based.  But that's purely conjecture.



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