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19990617: Image calculations and raster files

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  • Subject: 19990617: Image calculations and raster files
  • Date: Fri, 18 Jun 1999 13:59:34 -0600
>From: Tye Parzybok <address@hidden>
>Organization: Oregon State
>Keywords: 199906171817.MAA28605 McIDAS

Tye,

>I have a couple of questions in using McIDAS-X (latest version):
>
>1)
>
>I have been referencing an e-mail support document on your site:
>http://www.unidata.ucar.edu/packages/mcidas/users_guide750/McHTML.51.HTML#28484

OK.

>...and trying to import a raster ASCII file (of image brightness) into
>a GIS.

OK.  Presumably you are using something like AXFORM to dump out values
to an ASCII file?

>I'm almost there, but I need to know the limits (lat/lon) of the
>reprojected image (I used IMGREMAP ... PRO=RECT) to manually add to the header
>on .A01 file (brightness raster file).

You lost me here.  IMGREMAP remaps an image in one dataset to an image
in another.  I do not know of any option in IMGREMAP that adds information
to an ASCII file.

>How do I determine the lat/lon limits of an image?

For non rectilinear images this really makes no sense (i.e. what is the
lat/lon limit of an image that contains the earth's limb).  For a
rectilinear (or mercator) image you have a couple of options:

o display the image with no blowup/blowdown and interrogate the display
  for LAT,LON at its extremities (use the E command)

o look in the AREA file header and pull out the LAT,LON of a point and
  the LAT,LON delta inbetween pixels.  This couple with the number of
  pixels in the LINE and ELEMENT dimensions will allow you to calculate
  the LAT,LON at all points.

>2)
>
>I have several 1-km images that I would like to make a composite image
>of. In other words, I'd like to add (or average) the brightness values
>of each image pixel of several images to arrive at a single image. How 
>would I do this?

There are several ways of doing compositing using IMGOPER.  Example
McBASI scripts that will do composition in two different ways are contained
in GEWCOMP.MCB and GEWCOMP1.MCB which you can find in your ~mcidas/data
directory.

The basic idea is that you need an output image into which you will remap
and combine the two imput images.  The composition can not be done in
one step, however.

Here is the synopsis of the steps from the informational header of GEWCOMP.MCB:

REM ?      GEWCOMP.MCB basically:
REM ?        o gets and validates user inputs
REM ?        o makes a copy of the "standard" image; remaps the specified
REM ?          west sector (perhaps selected by time) into the standard
REM ?          projection
REM ?        o makes a copy of the east half of the "standard" image; remaps
REM ?          the specified east sector (perhaps selected by time) into the
REM ?          standard projection
REM ?        o composites the remapped east and west sectors using the MERGE
REM ?          option
REM ?        o displays the composite image if the user asked for it

It could be that GEWCOMP.MCB can do the job you want with no modifications.
If not, you can use it as a template to create a new script that does
exactly what you need.

>Thanks so much for your help,

You are welcome.

Tom