[gradsusr] An error occurred while displaying satellite data

[Charles Tai]

Dear Ricardo,
I've checked the size of both the IR and VIS imagery files.
They are not in the same size. (313601 for IR vs 313643 for VIS)
However, I did display the VIS images successfully after adding the option
entry you mentioned into the descriptor file.
Really appreciate your help.
Thanks a lot.
                                 Charles


2013/11/18 Ricardo Hallak <ricardo.hallak at iag.usp.br>

> 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
>
> ------------------------------
>
> *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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