[Opengrads-devel] LATS ported to GrADS v2 as an extension

[Arlindo da S. <da...@al...>]

All,

 With Mike's help I've been able to port the LATS interface as an extension
to GrADS v2.0.a7.oga.2. I used the opportunity do make a few enhancements
such as support for NetCDF-3, NetCDF-4/HDF-5 and HDF-4 all from the same
single executable, and support for NetCDF-4 compression. The UI has
simplified a bit, you no longer need to go through the "display" command.
The following UDCs are provided:

     *User*
  Defined
  COMMAND           Short Description                Function@Library
 ---------- -----------------------------------  --------------------------*
* set_lats   Set LATS parameters                  c_lats_set@^liblats.gex
 query_lats Query LATS parameters                c_lats_query@^liblats.gex
 lats_grid  Define LATS grid                     c_lats_grid@^liblats.gex
 lats_data  Write data to LATS file              c_lats_data@^liblats.gex*
* ---------- -----------------------------------  --------------------------


The lats4d.gs usage remains the same; it detects the version and use the
appropriate LATS command. Some additional information:

1) I fixed a bug which has been driving me crazy for almost 10 years: now
you can call it twice in a row without exiting grads.

2) I created an alias for the "convention" parameter called "format". These
are equivalent

    ga-> set_lats convention grib
    ga-> set_lats format grib

3) From the same single executable added several format options

    ga-> set_lats format netcdf    (same as coards which is now deprecated)
    ga-> set_lats format netcdf4  (this is actually hdf-5)
    ga-> set_lats format hdf4

4) Added a compression option with NetCDF

    ga-> set gzip 2       (the higher the number, the better the
compression)
    ga-> set shave 12  (number of bits to shave from float mantissa)

    These usually go hand and hand. If you set shave it will automatically
set gzip=2 if it has not been set already. I should be able to add this
feature to HDF-4 output as well, but this require a patch I got from the HDF
Group and I'd better leave the supplibs alone for now.

5) Made lats4d.gs aware of these new features. Try these:

% lats4d.sh -i model -o junk -format netcdf -v
% lats4d.sh -i model -o junk -format netcdf4 -v
% lats4d.sh -i model -o junk -format hdf4 -v
% lats4d.sh -i model -o junk2 -format netcdf -shave -v

Compare the file sizes. Notice that the file extensions are now consistent
with the file format. Mike is looking into adding GRIB-2 support so that we
can close the circle: conversion from/to any GrADS supported format.

I still have some work to do on documentation and create a comprehensive
test suite (I might be able to borrow from my GrADS v1.x test suite.) If
anybody out there would like to help test this, just check out from CVS:

% gacvs co -P Grads
% cd Grads
% make binstall

The lats4d.sh script is now included under opengrads/Contents and all should
work out of the box. I am not sure if I'll release this as v2.0.a7.oga.3 or
wait for 2.0.a8.

Jennifer: Is 2.0.a8 coming out any time soon?

  Cheers!

      Arlindo








-- 
Arlindo da Silva
da...@al...