Aquadopp transformation
I have some data with tilts pegged at the peak tidal speeds. Given that the vertical velocity is zero, can I recompute a horizontal speed equal to the square root of the sum of the Ve, Vn, and Vvert squares? Will the originally computed direction still be correct?
The question about direction is a little tricky because the tilt sensors are used to calculate the compass direction.
The compass heading is relatively insensitive to rotations in the plane of the magnetic vector. On the other hand, it is quite sensitive to rotations in the plane perpendicular to the magnetic vector. In other words, if the compass direction is around N or S (in the plane of the magnetic vector), an unmeasured pitch does not matter too much. If the compass direction is around E or W, the same unmeasured pitch will generate compass errors of about 1.5 degrees per degree of unmeasured pitch.
1.5 is a rough number for Southern Canada the potential errors are larger toward the magnetic poles and smaller toward the equator.
The compass heading is relatively insensitive to rotations in the plane of the magnetic vector. On the other hand, it is quite sensitive to rotations in the plane perpendicular to the magnetic vector. In other words, if the compass direction is around N or S (in the plane of the magnetic vector), an unmeasured pitch does not matter too much. If the compass direction is around E or W, the same unmeasured pitch will generate compass errors of about 1.5 degrees per degree of unmeasured pitch.
1.5 is a rough number for Southern Canada the potential errors are larger toward the magnetic poles and smaller toward the equator.
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