Are ENU coordinates corrected for magnetic declination?

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Are ENU coordinates corrected for magnetic declination?

Posted by Amanda Kahn at July 16. 2017

We deployed two Aquadopp Profilers earlier this year; both were set to record using ENU coordinates.  I performed compass calibrations of both beforehand, at the same latitude as our study site because I couldn't tell if the calibration procedure is used to account for magnetic declination.  At our site, that declination is about 18 degrees so can have a big effect on our ENU readings.  Does any internal processing account for that? Or should we correct for that now, in post-processing?

Re: Are ENU coordinates corrected for magnetic declination?

Posted by Steven Figueroa at September 19. 2017

Hi,

 

I cannot give you a definite answer, but in my lab we apply a rotation to the horizontal velocities to account for our local magnetic declination.  Then, a plot of N vs. E currents tend to match with the orientation in the map (a tidal channel).  I don't think the Aquadopps have GPS to let them know their coordinates to account for the magnetic declination, which varies with latitude as you say.

Re: Are ENU coordinates corrected for magnetic declination?

Posted by Cees Meijer at September 22. 2017

That is correct. Since the Aqaudopp sensors have no knowledge of their geographic location you will have to do the correction for magnetic declination yourselves. There is also no standard post processing software that does this so I suppose you will just manually have to correct all your readings.

 

 

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