Geoclue reports a heading of 0 when there's no compass available from SensorProxy
My system has a GPS, but no compass. According to the where-am-i demo tool I'm always heading North (0 degrees) even though my position changes as the GPS provides fixes and I'm walking around. According to the GeoClue documentation it should be reporting -1.0: https://www.freedesktop.org/software/geoclue/docs/gdbus-org.freedesktop.GeoClue2.Location.html
As a bit of background here. The compass sensor on the PinePhone cannot provide the necessary angle from magnetic north that other sensors can (in_rot_from_north_magnetic_tilt). Instead, it only provides x,y,z measurements of the magnetic field, which must be used to calculate the magnetic tilt with some user-generated calibration data. As a result, iio-sensor-proxy doesn't find the compass and GeoClue gives a value that doesn't match the documentation.
I think that GeoClue should either update its documentation to reflect the way the implementation works or it should handle the missing compass case and return the -1.0.