in binary/util.go [133:138]
func RelativeCoords2Bytes(lon float64, lat float64, xLon float64, xLat float64) []byte {
relLon := int(math.Round(DECA_MICRO_DEG_FACTOR * (lon - xLon)))
relLat := int(math.Round(DECA_MICRO_DEG_FACTOR * (lat - xLat)))
return append(Int2Bytes(relLon, 2, true), Int2Bytes(relLat, 2, true)...)
}