2.8.11.25. Bottom Tracking

2.8.11.25.1. Part I: CODAS binaries

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

1. lst_btrk: Extract the bottom track velocity data within the specified time range(s) from a CODAS database into a text file.

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

   • run lst_btrk lst_btrk.tmp

   • creates specified output file, eg. aship.btm

2. refabsbt Calculate ship displacement from both position data and bottom track velocity data in a CODAS ADCP database, averaged between consecutive fixes.

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

     • ensemble length must match database

   • run refabsbt refabsbt.tmp

   • creates aship.ref

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

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

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

python Btplot_script.py

Example:

Default Btplot_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 Btplot

## other parameters that can be chosen:
##   name            default
##   ------        --------------
##   dbname           (found in ../../adcpdb)
##   titlestr         (uses ADCP
##   proc_yearbase    (first year in database)
##   printformats               'pdf'
##   dpi                        100
##   outfilebase               'btcal'
##   ddrange                    'all'
##   step                       1
##   min_speed                  2
##   max_sig                    2.5
##   max_gap                    0.1
##   tol_dt                     0.02
##   min_depth                  25                #shallower for high freq
##   max_depth                  1500
##

BT = Btplot()
BT(btm_filename='aship.btm',
   ref_filename='aship.ref',
   cruiseid = 'ADCP',
   printformats = 'png',
   proc_yearbase='1993')

plt.show()

This appends a block of Bottom Track Calibration information to the file btcaluv.out:

ADCP bottomtrack calibration

Time range  99.29 to  99.42
   Calculation done at Tue Apr 23 02:52:40 2013
    step: 1
    min_depth:  25   max_depth: 1500
    min_speed:  2.0 m/s   max_sig:  2.5 std devs
    max_gap:  0.10 minutes   tol_dt: 0.02 (fraction)
unedited: 31 points
edited:   23 points, 2.0 min speed, 2.5 max dev
            median     mean      std
amplitude   0.9989   1.0013   0.0179
phase      -0.4306  -0.2666   0.9689

To change some of the calculation parameters, copy the file Btplot_script.py to another name, eg. Btplot_shallower.py and edit. For example, to change the following parameters …

• new output filename : outfilebase = ‘btcal_shallower’

• at slower speeds: min_speed = 1

• allow shallower minimum depth: min_depth = 15

• use shallower maximum depth: max_depth = 500

... replace the call to BT (above) in Btplot_shallow.py with these additions:

BT = Btplot()
BT(btm_filename='aship.btm',
   ref_filename='aship.ref',
   cruiseid = 'ADCP',
   printformats = 'png',
   proc_yearbase='1993',
   outfilebase = 'btcal_shallower',
   min_speed = 1,
   min_depth = 15,
   max_depth = 500)

Do not forget to add commas after each new line.

Run again:

python Btplot_shallower.py

Now the Bottom Track Calibration values have changed:

ADCP bottomtrack calibration

Time range  99.29 to  99.42
   Calculation done at Fri May 10 05:39:14 2013
    step: 1
    min_depth:  15   max_depth: 500
    min_speed:  1.0 m/s   max_sig:  2.5 std devs
    max_gap:  0.10 minutes   tol_dt: 0.02 (fraction)
unedited: 30 points
edited:   23 points, 1.0 min speed, 2.5 max dev
            median     mean      std
amplitude   0.9979   1.0010   0.0180
phase      -0.5754  -0.3598   1.0117

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

Summary:

before:
--------
unedited: 31 points
edited:   23 points, 2.0 min speed, 2.5 max dev
            median     mean      std
amplitude   0.9989   1.0013   0.0179
phase      -0.4306  -0.2666   0.9689


after:
-----
unedited: 30 points
edited:   23 points, 1.0 min speed, 2.5 max dev
            median     mean      std
amplitude   0.9979   1.0010   0.0180
phase      -0.5754  -0.3598   1.0117