RT_GPS_Pos_LLH_2 GPS Longitude and altitude
RT_GPS_Pos_LLH_2: 140, 3 (0x8C0320 + unit id) (0x303)
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Bytes 0-3: Longitude (degrees)
Bytes 4-7: Altitude (m)
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Longitude resolution is degrees * 1e-7.
Altitude resolution is m/1000.
Validity is provided by RT_GPS_Pos_LLH_1.