README file for IDL programs to handle GTE data
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version 1.10, Martin Schultz, 04/10/1999


1.) File formats

    GTE data files are stored in a specific ASCII format outlined in a
document available from the project office. The GTE tools suite currently
supports file types 0-2, i.e. no profile data. You MUST provide either
a sampling interval or seperate columns for start and stop time.
Some of the programs described below use hardwired default filenames,
although it is generally possible to specify the real filename as a command 
line parameter or keyword. The path structure that I have chosen for the
PEM Tropics B campaign is as follows:

    c:/data/gte/pem-tb/dc8/raw     raw ascii data files (almost as submitted)
                          /binary  individual species files in binary format
                                   supplemented by location information from
                                   the project data
                          /merges  this directory contains merged data files
                                   in both ASCII and binary format

2.) procedures

    Basically all processing of the GTE data requires the prior conversion
to binary format. Though this may seem a little cumbersome at the beginning,
it has two major advantages:
  - processing time is MUCH faster
  - the quality control filtering has only to be done once. After you converted
    a file you can be sure that it is in valid format.

2.1) gte_convert and gte_convertflight

    This program converts GTE files from ASCII to binary format and gives you a couple
of warnings and status information in the process. Use the second program to convert
all data sets from one flight. The first file you must convert is always the project
data, because this is used to provide the location information which will be merged into
all other data sets. The location information is stored in seperate binary files named
loc_*.bdt . GTE_CONVERT will ask you for the name of the associated location file.

2.2) gte_merge

    This program links together all files from one flight (or a user selection of files).
You can choose any file as a time reference or provide a reference sampling interval
with the reftime keyword:
      gte_merge,reftime=60       ; produces a 1 minute merge
Set the ASCII flag (gte_merge,/ASCII) to produce merges in the GTE format, default is to 
produce binary merges.

2.3) gte_explore

    This is the program to plot individual or merged binary data files. Basically, it is
just a small "wrapper" for the EXPLORE package which is described in a seperate documentation
in the Explore directory (idl_explore.htm).


2.4) other programs
    A couple of other programs that may be useful are:
    - gte_map : produce the color bubble maps
    - gte_profiles : plot vertical profiles for several species
    - gte_insertvar : insert a new variable into a binary data set
    - gte_delvar : delete a variable from a binary data set
    - gte_writeascii : convert binary data into GTE ASCII format