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.. UHDAS/CODAS restructured text document
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ADCP Data Quality: Monitoring and Calibration
-----------------------------------------------

   `Monitoring at sea`_
   `Calibration`_


.. _`Monitoring at sea`:

Monitoring
~~~~~~~~~~~~~~~~

At sea, there are three categories of monitoring:
 * `ADCP processing`_ (example: ocean velocity profiles)
 * `health of the components`_ (ADCP, accurate heading device)
 * `data acquisition`_




.. _`ADCP processing`:

(1) ADCP processing:
   
    * ADCP profile plots: 
    
       These are updated frequently at sea.  Each figure has several components.
       See `this link <lastens_annotated.png>`_ for an annotated figure.
       At sea, these are on the **Quick Links: Figures** link on the UHDAS
       home page, usually `here <http://currents/adcp>`_.

    
    * The profile plots should have a data timestamp not more then 10 
      minutes old.


.. _`health of the components`:
    
(2) health of the components:

    * heading correction

       If the ship has an accurate heading device as well as a gyro, 
       UHDAS will keep track of the difference between the two, and 
       plot it.  See `this link <gyrodh.png>`_ for an annotated example 
       of the figure. 
       See `this link <../../UHDAS_webdoc/ashtech_diagnostics.html>`_
       for more detail about Ashtech errors and how to recognize them.
       An accurate heading
       device might be Ashtech, POSMV, Seapath, Phins, Mahrs, or Octans.
       At sea, these are on the **Quick Links: Figures** link on the UHDAS
       home page, usually `here <http://currents/adcp>`_.


       .. NOTE:: Not all of these instruments have QC indicators

.. _`data acquisition`:

(3) data acquisition:

    * On the UHDAS computer console, "green is good" for the logging status.

      If a cable falls out or a feed quits coming in, the bar turns red
      ("red is rubbish")


    
.. _`Calibration`:


Calibration 
~~~~~~~~~~~~~~~~

The orientation of each transducer with respect to the bow 
must be determined for processing to proceed.  This is done 
at the time of a UHDAS installation using either previous 
data or a bottom track calibration run if there is no earlier
data from the instrument.  A new instrument is calibrated using
a bottom track run.


Over time, watertrack and bottomtrack calibrations are used to
determine whether this angle has changed.  If a heading correction
device exists and is working, it is not necessary to leave bottom
tracking on, and in fact you lose statistical robustness (increase
noise) in the ocean velocity data when bottom track is on, because
every other ping is looking for the bottom.  Bottom track is
detrimental to the velocity data if it is left on when the ocean floor
is out of range. In general, **turn off bottom track when the ocean
floor is out of range of ADCPs**

    
Monitoring calibrations with a UHDAS system
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    
Every day an email is generated and sent to the ADCP operator at
sea and intersted parties on land.  That email includes information
about the compter's health, processing status, and a data snippet 
that is plotted.  On land, the web site with this information is 
accessible `here <http://currents.soest.hawaii.edu/uhdas_fromships.html>`_.

Watertrack and bottom track calibration values are included in this email.
The hope is that values will be:
     
     - close to 1.0 for amplitude 
     - close to 0.0 for phase

See `this annotated example <btwt_caltxt.png>`_ for more details.


Please note these caveats:

    - Some cruises have no bottom track data, some have no 
      watertrack data, simply due to the cruise track.

    - Watertrack calibrations are by nature noisy and generally
      accumulate slowly.

    - These data are preliminary; there could be editing that has not
      yet been done that will clean up these values, for instance 
      some data may not have been flagged as bad below the bottom, 
      and if any underway bias exists (eg. from bubbles) it will hurt the 
      amplitude calibration.

    - There could be gaps in the heading correction device that are
      throwing off the phase calculation


**At Sea** the most recent watertrack and bottom track calibration assessments 
are available on the UHDAS home page, as well as a statement about the 
angles that were determined when UHDAS was installed.


Calibration Resources
^^^^^^^^^^^^^^^^^^^^^^

ADCP calibration resources include detailed discussions of calibration in 

       * the `original CODAS manual <../../local_doc/manual.ps>`_
       * the `original pingdata processing instructions \
         <../../codas_doc/CODAS_pingdemo.html>`_
       * `quick_adcp.py processing guide \
         <../../codas_doc/CODAS_quickdoc.html>`_

and these notes on

       * `bottom track calibration for a new ADCP installation \
         <../..//UHDAS_webdoc/Troubleshooting/btcaluv.html>`_