Heading - Aquadopp current meter
| Quote |
| Dear Sir/Madam, This is a quick enquiry regarding the output from one of your Aquadopp 3D Ocean Current Meters ... specifically with respect to the "Heading" output ... My presumption has been that if I take the arctangent of the quotient of the two horizontal current values, then I should arrive at the "same number" as in the Heading output ... after an allowance for the proper quadrant ... as these do not seem to match, nor even seem to give a uniform difference, am I making a fundamental error here ?? Can you please offer advice and set me straight on what I am doing wrong here ?? your assistance is much appreciated... |
You are looking at the difference between the direction of the flow and the direction of the X-axis of the instrument. The first is what you calculate based on the Atan of the two velocity components - assuming that you have collected data in ENU coordinates. The second is the direction of the compass - sort of like the direction your boat when you read the compass. Since the instrument is not necessarily pointing into the flow (unlike the boat), the two directions will usually not be the same.
Best regards,
Atle Lohrmann
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