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20041123: Read GOES 12 data



>From: address@hidden
>Organization: GMU
>Keywords: 200411231749.iANHn27j024490 McIDAS AREA GVAR navigation

Hi Ying,

I finally got some time to respond to your message.  Sorry for the
delay.

>I want to read the GOES 12 data downloaded by LDM. Until now, it's no
>problem to display the picture by reading out the data block in the
>file. But I'm not sure about the navigation block, which contains the
>information to geolocate the image.

To be sure we are clear, the images that are transferred by the LDM
in the UNIWISC (aka MCIDAS) datastream are PNG compressed AREA files.
The various headers included in a standard AREA file are contained at
the beginning of the product followed by the comment card section
that usually is found at the end of an AREA.  The last portion of
the product is a PNG compressed image.

>From the link
>http://my.unidata.ucar.edu/content/software/mcidas/miscdocs/area.html
>on Page 19, it says the word 1 of NAV block will be
>'GOES'/'PS'/'LAMB'/' '.  But what I found from my file is 'GVAR'.

area.html is old.  area2.html contains makes reference to GVAR:

McIDAS miscellaneous docs
http://my.unidata.ucar.edu/content/software/mcidas/miscdocs/misc_docs.html

Description of AREA file format for GOES GVAR, GOES-7 and METEOSAT PDUS
http://my.unidata.ucar.edu/content/software/mcidas/miscdocs/area2.html

>So I'm not sure if the explanation of other words is correct for my
>file.

Please use area2.html, or consult the McIDAS Programmer's Reference
Manual:

McIDAS Programmer's Reference Manual (SSEC)
http://www.ssec.wisc.edu/mug/prog_man/prog_man.html

>The GOES data is in it's own projection called "GVAR projection",
>right?

The current satellite images in the IDD UNIWISC stream are from the
GVAR series of GOES platforms, yes.

>How can I do the projection transformation so that maps from
>other sources can be layered on top of it?

You would have to write code that can interpret the navigation parameters
and correctly map satellite coordinates to earth coordinates.  This is
no simple task.  The full documentation for the GVAR navigation is
contained in documents referenced in the area2.html file:

Operations Ground Equipment,
Internal Specification, DRL 504-02-1 Part 1,
Specification No E007020, released February 9, 1994,
Space Systems/Loral,
3825 Fabian Way, Palo Alto, CA, 94303-4604.

>Is this projection available in some GIS software like ArcGIS?

I don't know if any GIS system supports satellite projections.  My
understanding is that GIS systems typically deal with conical projections.

One possibility is to use the current release of McIDAS which can
access data that has the GVAR navigation format and remap it into some
conical projection.  Then, use a different McIDAS facility to output
the image into a format that _is_ recognized by GIS, GeoTIFF.  In order
to use McIDAS, you would need to register as a Unidata user (which you
have already done); download McIDAS; build, install, and configure
McIDAS, and hen learn how to use it.  This can be daunting since McIDAS
is a _big_ package, but once you get the hang if it it is not
difficult.

>Hope I specified it clearly. Thanks a lot!

Again, sorry for the big delay.

Cheers,

Tom
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