[BurningFrog]

GPS already gives you altitude in addition to longitude and latitude, so I don't understand what the air pressure adds.

[tqi]

Vertical error for GPS is about 2X to 3X more than horizontal error[1], so the barometer helps correct that.

[1] https://www.nstb.tc.faa.gov/reports/2020_Q4_SPS_PAN_v2.0.pdf...