Payload

Device ID: 1 byte (0-255)

(Latitude: 3 bytes (0-90 degrees represented by a signed (3 byte integer) gives ~1.1m resolution at 56 degrees

Longitude:4 bytes, ( 0-180 degrees represented by 4-byte signed integer)

battery level: 1 byte (3.3-4.5v mapped onto 0-255) - probably overkill resolution

Speed over ground 1 byte (0-63.75kph mapped on 0-255)

COG - 1 byte 0-360 mapped on 0-255

#satellites (4 bits) of one byte

#valid fix (1 bit) of one byte

#panic button (1 bit) of on byte

# gpio flags 2 bits spare

Total 12 bytes

LoRa Parameters

With a set of 'long range' LoRa parameters (SF=10, BW=125kHz,CR=4/8), implicit header and a 12 Byte payload, the time on air is 280ms (610bps equivalent bit rate).