Barometer temperature correction

[Pietero]

I'm making a new app for kitesurfing and wanted to use the barometric sensor to determine altitude to count jumps.

However, the barometer is useless when you do not have acces to the temperature. A minor temperature change causes the barometer sensor to drift. Please see further info in my kite surfing post: https://community.fitbit.com/t5/Feature-Suggestions/Kitesurfing/idc-p/2971058#M184277

Are there any plans to give acces to the temperature sensor? Or.. Are there plans to correct the barometer output for temperature changes?

[JonFitbit · Accepted solution]

Hi, thanks for the feedback.

I did some digging internally and temperature is factored into the readings from the barometer.

[Pietero]

Great to hear that is factored within the barometer. I think it is a good idea to mention that in the api documentation.

Though I don't notice that it is factored within the device API. I'm still experiencing a drift  I Assumed that the OS uses temperature correction since this is necessary to count floors.

Below is a graph showing the calculated altitude. At the red line, i Took off the watch so the temperature of the watch was going down. This graphs shows the the barometer is not properly corrected for temprature differences.

The formula for altitude used is: This is the general altitude calculation for 15 degrees celcius.

return (1 - Math.pow(reading/referencePressure,0.190284))*44307.694; 

[JonFitbit]

It sounds like the sensor isn't going to be suitable for this type of use case. We use it to calculate a relative altitude change in a brief period of time. With this type of MEMS sensor, it's expected to have drift with temperature of at least a few millibar.

[3v1n0]

Can you be more precise on this?

Is it the pressure value returned always assuming that the temperature is set to 15° or what?