2.8.11.24. Water Tracking

2.8.11.24.1. Part I: CODAS binaries

Use CODAS binaries to stage the data for watertrack calibration calculation. This has not changed since the original Pindata demo.

1. timslip Detect ship accelerations and turns from ship velocity,

   as recorded by the ADCP, and from position fixes. It can be used to derive an estimate of the time difference between the ADCP ensembles and the satellite time. It also provides estimates of the amplitude and phase of the transducer misalignment.

   Make changes in timeslip.tmp to extract more points for the watertrack calibration calculation, for example: allowing a slower ship-speed transition, or less smoothing before extracting the points. An example of this is here.

   • edit timslip.tmp (documented in timslip.cnt)

   • run timslip timslip.tmp

   • creates specified output file, eg. aship_7.cal

The default timslip.tmp is shown below (for database name aship):

fix_file_type:      simple
fix_file:           ../../nav/aship.ags

reference_file:     ../../nav/aship.nav
output_file:        aship_7.cal

year_base=          1993
min_n_fixes=        7 /* 5 7 9 */

n_refs=             7 /* 5 7 9 */

i_ref_l0=           1
i_ref_l1=           2 /* 1 2 3 */
i_ref_r0=           5 /* 4 5 6 */
i_ref_r1=           6 /* 4 6 8 */

up_thresh=          3.0        /* m/s */
down_thresh=        3.0        /* m/s */
turn_speed=         2.0        /* m/s */
turn_thresh=        60         /* degrees */

dtmax=              360        /* seconds, for 300-second ensembles */
tolerance=          5.e-5      /* days, about 5 seconds */
grid:               ensemble

use_shifted_times?  no

2.8.11.24.2. Part II: Python (used to be Matlab)

Use Python to calculate water track calibration values and make plots. This replaces the Matlab program calladcpcal_tmp.m.

Edit the file Wtplot_script.py Run the Python py typing:

python Wtplot_script.py

Example:

Default Wtplot_script.py for pingdata demo:

#!/usr/bin/env python

## written by quick_mplplots.py -- edit as needed:

## cruiseid      is 'ADCP'
## dbname        is 'aship'
## proc_yearbase is 1993
## printformats   is 'png'

import matplotlib.pyplot as plt

from pycurrents.adcp.quick_mplplots import Wtplot

## other options that can be chosen
##
##       name                    value
##      -------------          -----------
##        cruiseid             'ADCP
##        printformats         'pdf'
##        dpi                   100
##        outfilebase          'wtcal'
##        statsfile            'adcpcal.out'
##        comment              '#'
##        ddrange              'all'
##        clip_ph               3,
##        clip_amp              0.04
##        clip_var              0.05
##        clip_dt               60
##        clip_u                [-100,100]
##        clip_v                [-100,100]

WT = Wtplot()
WT(cal_filename = 'aship_7.cal',
  printformats = 'png',
  cruiseid = 'ADCP',
  proc_yearbase = '1993')

plt.show()

This appends a block of Water Track Calibration information to the file adcpcal.out:

ADCP watertrack calibration
##
 Time range  98.05 to  99.32
   Calculation done at Tue Apr 23 02:52:40 2013
   delta-u min = -100.00, max = 100.00
   delta-v min = -100.00, max = 100.00
   clip_amp = 0.04,  clip_ph =  3.0
   clip_dt =   60,  clip_var = 0.050
Number of edited points:  15 out of  17
   amp   = 0.9940  + 0.0172 (t -  98.8)
   phase =   0.24  + -0.9924 (t -  98.8)
            median     mean      std
amplitude   0.9930   0.9940   0.0161
phase       0.1350   0.2367   0.9394
nav - pc    4.0000   3.1333   5.5274
var         0.0080   0.0104   0.0066
min var     0.0080   0.0097   0.0067
delta-u     0.3700   0.7433   2.1442
delta-v     1.7500   0.4953   4.1361

To change some of the calculation parameters, copy the file Wtplot_script.py to another name, eg. Wtplot_slower.py and edit. For example, to change the following parameters:

• new input filename (if timslip was changed and used a different output file): cal_filename = ‘aship_5.cal’

• new output filename : outfilebase = ‘wtcal5_slower’

• more phase clipping: clip_ph = 2

... replace the call to WT (above) in Wtplot_slower.py with these additions:

WT(cal_filename = 'aship_5.cal',
  printformats = 'png',
  cruiseid = 'ADCP',
  proc_yearbase = '1993',
  outfilebase = 'wtcal5_slower',
  clip_ph = 2)

Do not forget to add commas after each new line.

Run again:

python Wtplot_slower.py

Now the Water Track Calibration values have changed:

ADCP watertrack calibration
 ##
  Time range  98.05 to  99.73
    Calculation done at Fri May 10 08:43:11 2013
    delta-u min = -100.00, max = 100.00
    delta-v min = -100.00, max = 100.00
    clip_amp = 0.04,  clip_ph =  2.0
    clip_dt =   60,  clip_var = 0.050
 Number of edited points:  20 out of  24
    amp   = 0.9861  + 0.0240 (t -  98.9)
    phase =   0.18  + 0.3759 (t -  98.9)
             median     mean      std
 amplitude   0.9820   0.9861   0.0208
 phase       0.2305   0.1794   0.9147
 nav - pc    2.0000   2.9000  10.1872
 var         0.0075   0.0086   0.0043
 min var     0.0060   0.0072   0.0041
 delta-u     0.4350   0.0585   2.0352
 delta-v    -1.3150  -0.3795   3.7571

This is just a demonstration of how th make the changes. You have to decide what to apply.

Summary:

before:
-------
Number of edited points:  15 out of  17
   amp   = 0.9940  + 0.0172 (t -  98.8)
   phase =   0.24  + -0.9924 (t -  98.8)
            median     mean      std
amplitude   0.9930   0.9940   0.0161
phase       0.1350   0.2367   0.9394


after:
-----
Number of edited points:  20 out of  24
   amp   = 0.9861  + 0.0240 (t -  98.9)
   phase =   0.18  + 0.3759 (t -  98.9)
            median     mean      std
amplitude   0.9820   0.9861   0.0208
phase       0.2305   0.1794   0.9147