CODAS+UHDAS Documentation


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Calibration Consistency

The following example shows various places within the ADCP processing directory where the same number will show up for watertracn or bottom track calibration. In this example, the calibration is indicating a correction of about -3deg. positive is clockwise).

  1. cal/watertrk/adcpcal.out:

    Number of edited points:  16 out of  28
       amp   = 0.9991  + -0.0266 (t - 101.3)
       phase =  -3.00  + 0.0763 (t - 101.3)
                median     mean      std
    amplitude   0.9970   0.9991   0.0169
    phase      -2.9865  -2.9983   0.8038       <==== about -3deg
  2. “apply phase correction”: apply the number found in #1: --steps2rerun rotate --rotate_angle -3.0
  3. the phase in the watertrack calibration picture (cal/watertrk/wtcal1.png)

  4. If you were to make a file with time-dependent heading corrections to apply, you make a file called (for instance) new_hcorrs.ang, with 2 columns (decimal day, angle) and the angles should be around -3.0. Then the effect of the command below is the same as #2 above:

    rotate rotate.tmp

    For instance:

    ## begin rotate.tmp
       DB_NAME:       ../../adcpdb/a_nf
          LOG_FILE:      rotate.log
          TIME_RANGE:    all
               year_base=          2015
               time_angle_file:   new_hcorrs.ang
               amplitude=          1
               angle_0=            0
  5. When redoing the heading alignment angle, the value of -3.0 (i.e. what watertrack or bottom track estimated) is used like this:

    transducer_angle = xxx.yy
    calibrations (watertrack and bottom track) indicate a value of -3.0
    new_transducer_angle = xxx.yy - (-3.0)

Time-dependent Heading Correction

If an accurate heading device exists, that will be the best final reference for heading. Watertrack and bottom track calibration indicate the constant offset necessary to corectly align the transducer.

If there is no accurate heading device, you might end up with a situation like the one below, with a mix of watertrack and bottom track points suggesting a time-dependent calibration:

time-dependent heading correction from watertrack and bottom track

After writing out a file with the proper format and applying the correction, the remaining calibration is noisy, but does not indicate any biases or anything else we can fix.

watertrack and bottom track after time-dependent calibration

Here’s another cruise with watertrack and bottom track data from two instruments, showing a time-dependent correction that can be made (in the absence of an accurate heading device).

time-dependent heading correction from watertrack and bottom track