Recalibration of Barometer

[Holton181]

Hi,

I would like a more easy way to calibrate the barometer in flight without the need to restart FiF.
Now calibration is done several steps down in the preferences, with a non-intuitive pressure calibration value (the slider doesn't work for negative values by the way), also forcing the app to restart.

An implementation could be similar to that in another excellent navigation app, Oruxmaps. For instance, when long tap the altitude indication a new list item could be added to that menu, like "Baro Cal." or something. Selecting that a popup where you are asked to enter your present altitude (preferably taken from the aircraft altimeter with the same QNH as FiF) and hit "Apply" or similar. FiF then performs the calculations and apply the correction to the pressure (without a restart!!!), making your FiF altimeter read the same value as the aircraft counterpart with using the same QNH.
The manual calibration through preferences can still be possible in parallel.
Oruxmaps also has the functionality to correct the recorded track between the last calibration and the new, with the assumption the lost calibration during that time has been linear. If such functionality would be implemented the QNH for the two calibration points need to be the same (maybe FiF can request a calibration automatically whenever changing QNH, and applying the calibration before making the new QNH effective?)


Motivation:
1) An electronic barometer needs to be calibrated from time to time, quite often for what I know.

2) The barometer can only be used in non-pressurized cabins. As soon as you start moving (relative to the air) there will be a suction phenomena in non-pressurized cabins making the pressure slightly lower than ambient. The result will be that the barometer, freshly calibrated standing still on the ground, will over-read slightly. The same will happen to the aircraft altimeter and ASI if the static port is blocked and you need to use the alternate, often located in the cabin, or break the glass of the VSI.
So when you have reached your cruising speed and altitude, preform a calibration and FiF will give you the same altitude as the aircraft. If you change speed (and possibly altitude) the strength of the suction will change and a new recalibration might be needed.


BR
/H

[kitercuda]

Restarting is needed, but I want to change calibrating - it will be available ousdie of preferences.
I want also implement saving calibration for different speed - because usually if ground speed is 150 knots, cabin pressure is several mbar less. This will be saved to each aircraft separately.

[Holton181]

Sounds like a good solution for the calibration. Automatic switch depending on the GS I guess?
Or would it be a possibility to use linear regression with a couple of calibration/speed pairs to determine an approximate calibration vs speed function?
/H