Nortek Aquadopp Compass - Positive clockwise? or.. ? (what does due-east correspond to in degrees)

Hello All,

Have some velocity data recorded by a Nortek Aquadopp ADCP, without the proper heading data. We recorded in XYZ and I am now trying to convert to ENU using the transform.m here on this site.

My question is fairly simple, I hope:

We kept our instrument pointed approximately due east (magnetic) during the deployment. But what angle does this correspond to? 90deg ? I see in the script that it does this for heading: hh = pi*(heading-90)/180; so my my 90deg turns to 0. I am a little confused on this.

If anyone could help me, that would be great.

cheers,

Dear Charlie

The compass scale and the radian scale rotates in the opposite direction and with a 90 deg. offset.  When we say North (0 deg), this corresponds to pi/2 in the world of radians (which is where the cosine and sine functions live).  And East (90 deg.) corresponds to 0 radians.  In other words, the 'heading' in the formula is the compass direction as we use it in our everyday language and 'hh' is in units of radians - which can then be used in the transfer function included in the script. 

Best regards, Atle Lohrmann

So just to clarify, If I insert a line saying heading=90, before the hh = pi*(heading-90)/180; That will correspond to due East?

ALSO: The transform.m matlab file on here appears to be for a stationary ADCP, is there a version of this file that accounts for a changing heading/pitch/roll ?

cheers,

Previously Atle Lohrmann wrote:

Dear Charlie

The compass scale and the radian scale rotates in the opposite direction and with a 90 deg. offset.  When we say North (0 deg), this corresponds to pi/2 in the world of radians (which is where the cosine and sine functions live).  And East (90 deg.) corresponds to 0 radians.  In other words, the 'heading' in the formula is the compass direction as we use it in our everyday language and 'hh' is in units of radians - which can then be used in the transfer function included in the script. 

Best regards, Atle Lohrmann

Dear Charlie

Yes, you got it right.  As for making a script that can do variable pitch and roll, you simply have to write the appropriate loops over all your data points, i.e. you have to generate a new transform at each time step.

Best regards, Atle Lohrmann