Context: I am using a (version of) poly_pkt_forwarder on a PiZeroW with a RAK831 and a MAX-7Q GPS and the AurelGP antenna.
The height (altitude) to specify for a gateway location might be a bit ambiguous.
My GPS gives both:
- Altitude, Meters, above mean sea level
- Height of geoid (mean sea level) above WGS84 ellipsoid
The Semtech GPS utility code used in the poly_pkt_forwarder uses the “Altitude, Meters, above mean sea level”, so it seems that this is the one to use in the config file too.
Before I dug into the code I wanted to specify the antenna height above ground level there. Which is some 4 meter for me. However, height above sea level is some 8 meter.
And to add to the confusion. There are also fields in the TTN console to specify lat/lng/alt. What are they for? How to relate them to the ones configured in (or measured by) the gateway?