compass, pitch and roll update - Aquadopp

I am aware that it is possible to program the frequency that the compass is updated.  When this occurs does the pitch and roll also update?  I have used a Aquadopp to measure velocities in 'waves mode'.  Compass update frequency was set to every second.  Waves were sampled every 5 mins, 512 samples at 2Hz.  I seem to only have compass, pitch and roll recordings before each burst though (i.e. every 5 mins).  As the instrument was moving during the burst i was hoping to use the pitch and roll record to correct these data.  (i have a record of instrument velocities to subtract to give true currents).

Any ideas appreciated.

Roger

Hi Roger,

It is correct that you can program the update frequency of the compass, and when the compass is read so is the tilt sensor. However, this is only possible for current profile measurements. When collecting wave data only the pressure sensor, the three velocity components, and the analog inputs are sampled at the selected update frequency. The wave calculation software assumes that the instrument was not moving while the wave data are collected, and this is why it only reads the compass and tilt sensor at the start of each wave burst. This means, unfortunately, that you can not correct the wave data collected by an Aquadopp Profiler that moves while it was measuring waves.

The AWAC. on the other hand, can be set to measure in what we call SUV mode. This allows motion of the instrument while wave data are collected, due to that for each and every sample a 3D velocity vector, corrected for heading and pitch/roll fluctuations, is calculated.

Best regards,

Ketil Horn