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DeveloperPermalink Reply by Randy on January 26, 2012 at 6:30pm

I'm not an arduplane expert (I deal more with arducopter) but I don't believe that GPS is used at all for altitude because it can be very inaccurate at times.  I think it completely relies on the barometer.

The barometer has temperature compensation in the code but not sure really if that would cause issues.

The barometer on the APM2 is far better by the way.

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Permalink Reply by James masterman on January 28, 2012 at 11:12pm

Thanks Randy. I'll have to play around a bit more. I have another plane with another APM1 in it that doesn't seem to have the same problems. It runs much cooler inside, which is why I thought that might matter.

I will upgrade to APM2 in a few months when they are easier to get.

 

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Permalink Reply by Joseph on March 16, 2012 at 6:32am

Temp. can affect alt. On a hot day your density alt will be much higher then the actual alt. Here in New Mexico we are at 4465 ft msl or above sea level, and on a warm day our density alt will be at over 7000ft msl. This will effect the Baro metric pressure and will cause the APM to shoe higher then what it is.

Just my 2 cents.

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Permalink Reply by John Moore on April 19, 2012 at 9:49am

Does anyone know if you can adjust a parameter to correct this?

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Permalink Reply by David Ardis on March 25, 2012 at 3:31pm

I have had the same problem and discovered the altitude varies depending on the speed of the aircraft. Basically i was pressurising the inside of the plane. I solved the problem by connecting the pressure sensor to the static line of the pitot

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Permalink Reply by Tom in ON on March 25, 2012 at 4:13pm

@ David- how can you connect the barometer on the APM2 to the static pitot? It's mounted on the board and do not think it has port connections.

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Permalink Reply by James masterman on March 25, 2012 at 8:14pm

I'd be interested to know how to do this. The APM1 also doesn't have direct pitot tube connections to the barometer, so I'm not sure how you would do it.

 

I think temp may have some bearing as Joseph said. We have had some very hot days here, sometimes over 40C, and on these days the home altitude seems to be even more offset (up to 30m when it should be 10m)

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