[gradsusr] An error occurred while displaying satellite data

[Ricardo Hallak]

Hi, 

maybe your file has some problem in its last line of 560 bytes (corrupt data or lacking of data). 
However, the problem could be in your procedure in taking the header away. 
Your .ctl says that the image has 560 x 560 pixels of 1 byte each = 313600 bytes. 
Location 313040 + 560 bytes = 313600 bytes, which indicates that GrADS was looking for the last 560 bytes (in relation to what your .ctl says) when the problem was detected. 
If the .ctl works well with the IR image, it should work with the VIS images as well, which is something (kind of) strange if not. 
Please, check if the VIS images have the same sizes that the IR images (313600 bytes in size, I guess) in the disc system. They should have. 
Other test to try: 
Instead of taking away (manually I suppose) the header of files, you can use this optional entry for your control file: 
THEADER lenght_of_header 
Doing this way, the header will automatically be skipped by GrADS. 

Hope this helps or gives you some other idea to solve the problem, 
Ricardo 

----- Mensagem original -----

> De: "Charles Tai" <zhong2101 at gmail.com>
> Para: gradsusr at gradsusr.org
> Enviadas: Sexta-feira, 15 de Novembro de 2013 2:47:39
> Assunto: [gradsusr] An error occurred while displaying satellite data

> Dear GrADS users,
> I'm trying to display satellite images of pgm format with GrADS.
> These are what I did for that:
> 1. Take away the header of pgm file to prevent of the geographic
> shifting.
> 2. Write a description file (as the attached file) for GrADS.
> These procedures performed well in displaying IR images, but did not
> work for vis images.
> Here are the error message I got from it:
> ---------------------------------------------------------------------
> Low Level I/O Error: Read error on data file
> Data file name = ./sat/MTS212%m2%d2%h2VIS.pgm
> Error reading 560 bytes at location 313040
> Data Request Error: Error for variable 'mtsat'
> Error ocurred at column 1
> DISPLAY error: Invalid expression
> Expression = mtsat
> ----------------------------------------------------------------------
> Does anyone have similar experiences like this?
> I would appreciate any help.
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