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20040121: 20040120: GEMPAK and area files.

>From: Mark Tucker <address@hidden>
>Organization: UCAR/Unidata
>Keywords: 200401211935.i0LJZfp2002666

>
>> The 2 byte entries for GOES 12 may or may not be in your imgtyp.tbl
>> file depending on what version of GEMPAK you have.
>>
>> The entries would look similar to:
>> GOES12               VIS           0  30240     78      1      2 GRAY
>> GOES12               IR2           0    255     78      2      2 GRAY
>> GOES12               IR3           0    255     78      4      2 watvap.tbl
>> GOES12               IR4           0    255     78      8      2 GRAY
>> GOES12               IR5           0    255     78     16      2 GRAY
>> GOES12               IR6           0    255     78     32      2 GRAY
>> GOES12               IR4           0    255     78    128      2 GRAY
>>
>> Also, depending on whether or not your files have the expected
>> calibration information, you may get an all black image
>> (which I have created a fix for in the display drivers).
>> If you get that, we'll have to update your distribution.
>
>After editing the imgtyp.tbl, it looks like we're getting an all black
>image now with gpmap.  We're currently running gempak 5.6k.  Is the fix
>for the display drivers found in 5.6l or is that a patch I'd have to
>apply?

The modification will be in the 5.6.m/5.7.1 distribution (forthcoming).
I would have to create a patch if this were the problem. But first,
check below.
>
>Also, the only projection that seems to work is "sat".  The SAT
>projection gives us a us map and lat/long lines that appear "sloped" to
>the north (with the black satellite image).   If any other projection is
>specified, it does not appear to load the image (the line at the bottom
>describing the date and time of the data does not appear).

The SATFIL variable is only used when PROJ=sat. GEMPAK only
displays images in their given projection. 

>
>> The 2 numbers that specify the data range are dependent on
>> how the values are found in your files. For example, the
>> range of 0 to 30240 for visible is based upon the
>> raw values in the data files- but yours may be different.
>
>How would I determine what the data range values are?

Later versions of GEMPAK have a program "arinfo" that 
can dump out the data range. If you get all black, then
it sounds like you want the data range 0 to 255.
If you were getting all white, then the data values would be much larger
than 255, so the 0 to 1024 or 0 to 30240 would be more likely.

Steve Chiswell


>
>Mark Tucker
>Meteorology Dept. Systems Administrator
>Lyndon State College
>http://apollo.lsc.vsc.edu
>address@hidden
>(802)-626-6328
>
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