20051101: McIDAS-related questions (cont.)

>From: Unidata Support <address@hidden>
>Organization: UCAR/Unidata
>Keywords: 200510212351.j9LNpI7s028398 McIDAS MAKEAREA MAKNAV

Hi Mekonnen,

Here is a quick update on your goal of importing ASCII data output
by IDL back into McIDAS AREA files for visualization.

In a previous response to you, I noted that the only work needed was a
modification to the McIDAS application MAKNAV.  I was overlooking the
requirement that the data to be read by MAKEAREA be binary, not ASCII.
The operative portion of the MAKEAREA online help (HELP MAKEAREA) is:

  Remarks:
  MAKEAREA converts a flat file of brightnesses (1, 2, or 4-byte data)
  into a 1-byte AREA scaling the data appropriately

"flat file of brightnesses (1, 2, or 4-byte data)" means that the
data needs to be 1, 2, or 4 byte integers.

So, you will need to convert your ASCII output into binary files
before they can be imported into an AREA by MAKEAREA.  Is this
possible?

Also, I am curious about what calculations you made in IDL other
than creating monthly mean temperatures?  If that were the only
calculation you made (which I doubt), you could have used IMGOPER
directly on the AREA files you downloaded:

HELP IMGOPER
IMGOPER -- Applies mathematical functions to image data
  IMGOPER sdataset1..sdatasetn ddataset <keywords> "comment
 ...

Creating an average (as opposed to mean) for multiple images is
quite easy:

IMGOPER MYDATA/IMAGES.2001 MYDATA/IMAGES.2002 MYDATA/IMAGES.2003 
MYDATA/IMAGES.4000 COEF=0.333

This will divide the brightness values in the first three images by
3 and add them together (the default operation for IMGOPER is ADD).
The result, stored in MYDATA/IMAGES.4000 is the pointwise average of
the values of the first three images.

Cheers,

Tom
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