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updating Topography for CODAS
-----------------------------

The installation instructions include a quick-download of previously
extracted topography.  If for some reason you want to know how we
did that, or want to update it yourself, the instructions are below.


-----

A full Python CODAS installation requires topography that our python
programs can read.  You can use ETOPO or Smith-Sandwell topography
this purpose, but you must follow instructions for download and
installation (or UH Python code will not be able to read it).  You
must have compiled pycurrents (previous steps) before you can extract
topography.


We use two topography products, ETOPO and Smith-Sandwell.
You can get one or the other, or both.  Etopo has the advantage
of being global, and is probably adequate for many purposes.


Present versions we can parse are


(1) ETOPO:

    - go to http://www.ngdc.noaa.gov/mgg/global/global.html
    - There are lots of versions, but the one we support is this **ETOPO1 Ice Surface** at `this location <http://www.ngdc.noaa.gov/mgg/global/relief/ETOPO1/data/ice_surface/grid_registered/binary/etopo1_ice_g_i2.zip>`_

(2) Smith Sandwell:

    - go to   http://topex.ucsd.edu/WWW_html/mar_topo.html)
    - get **Global Topography V18.1** at `this location <ftp://topex.ucsd.edu/pub/global_topo_1min/topo_18.1.img>`_



The Etopo version keeps changing
and you may have to edit the python code to get the right version number.
Feel free to ask how to do this, or give it a try.  You need to
change the ``18.1`` above, and then recompile pycurrents


Installation:
~~~~~~~~~~~~~~~~~

(1)

    - make a directory adjacent to the UH programs directory,
    - it must be called ``topog``
    - inside ``topog`` make two directories
                   ``etopo``
                   ``sstopo``


    - ETOPO:

      * move the ETOPO file (``etopo1_ice_g_i2.zip``) into the etopo directory:
      * unzip there (``etopo1_ice_g_i2.bin,etopo1_ice_g_i2.hdr``)


    - Smith Sandwell:

      * move the Smith-Sandwell file (``topo_18.1.img``) to the sstopo directory

(2)

    - in a shell window, with all environment variables set correctly,
      change directories to ``/home/adcpcode/programs/pycurrents/scripts``
      (if the UH programs directory is ``/home/adcpcode/programs``)

      run:

            ``python topo_sub.py``

    - this should generate 2 more files for each type of topography.
      (it takes a long time). Then you should have:


::

      (alongside these)

          programs/codas3/[etc]
          programs/pycurrents/[etc]
          programs/uhdas/[etc]
          programs/onship/[etc]

      (new)

          topog/sstopo/topo_18.1.img
          topog/sstopo/topo_18.1s3.img
          topog/sstopo/topo_18.1s9.img

          topog/etopo/etopo1_ice_g_i2.bin
          topog/etopo/etopo1_ice_g_i2_s3.bin
          topog/etopo/etopo1_ice_g_i2_s9.bin

(3) The ``topog`` directory should be
`linked (or copied) <../codas_config/topo.html>`_
to the location appropriate for your intallation style.