How to set altitude to 0 before fly

[Marek]

My altitude before fly is no "0". Usula su + or - 2, 3 or 5 meters. Sometimes also 15. This nakes problem with setting altitude in GS points.
Thank with help.

 

[flyNfrank]

Calibrate the compass before flight. After compass has completed calibration process, power down your quad and back up again. Your altitude should be ok at this point.

 

[N017RW]

The compass has no bearing on altitude measurement.

Altitude is measured by a barometer in the IMU via atmospheric pressure changes.

 

[Marek]

Compass Calibration does not help.

 

[paulajayne]

Altitude is based on barometric pressure and a reading is taken on start up. So a restart of the quad will reset it, but it will vary as the pressure changes at ground level. Height is displayed as AGL (above ground level).

 

[N017RW]

I cannot say this will fix your issue but IMU calibration would be the most likely to have any effect on the baro-altimiter as that is where it is located.

I do not have OSD so it is unclear to me that if the pressure changes from the time of IMU calibration to the time of flight this will result in the slight errors you are seeing.

 

[paulajayne]

I do not have OSD so it is unclear to me that if the pressure changes from the time of IMU calibration to the time of flight this will result in the slight errors you are seeing.

At 0m, the standard barometric pressure is 101 kPa (760 mmHg)
At 15m, the standard barometric pressure is 101 kPa (758 mmHg)

Note how very small the difference the pressure is in mmHG and so small that the KPA reading is the same.

So a very small difference in air pressure will give a height difference.

I am not sure if the Phantom is displaying the height from GPS coordinates or its internal barometer, but, would be inclined to think it should be the GPS system as prime and Baro as secondary.

HTH

 

[Jstic]

Restarting the quad(battery off then on) almost always resets the altitude to near 0 for me. Compass calibration does nothing to correct it.