...
sonic: Vazimuth = magnetic + declination - 90
(Vazimuth is the direction that the sonic V axis is pointing)
prop: azimuth = magnetic + 1.3 + 180
...
sonic: Vazimuth = magnetic + declination - 90
(Vazimuth is the direction that the sonic V axis is pointing)
prop: azimuth = magnetic + 1.3 + 180