20001023: IMGREMAP: MAG= vs RES=

>From: Jason Allard <address@hidden>
>Organization: PSU
>Keywords: 200010240345.e9O3jC425238 McIDAS-X IMGREMAP MAG RES

Jason,

>I was wondering if you could help me with the difference between the mag and
>res keywords of the imgremap command.  I guess I was under the assumption that
>mag (magnification) would change the size of the image, but res (resolution)
>would actually change the resolution of the image (e.g., 4km to 8km).  But the
>mcidas manual I have leads me to believe that the mag keyword can affect the
>resolution.

The MAG= keyword does not change the size of the output image; that
is specified by the SIZe= keyword.

The effect of MAG= is to replicate the pixes by the MAG= value. If you
use a positive MAG= value, then pixels will be replicated by value times.
A negative MAG= value will sample the image by a value measure.

>Basically, what I need to do is change the resolution of a vis
>image (now 4km) to 8km so that it matches the resolution of the IR image.  I
>need to have the resolutions.

Since you are probably going to do a pixel-by-pixel comparison of the
VIS and IR images, you will want to:

o make a copy of the IR image, say in the dataset element MYDATA/IMAGES.1234:

  IMGDISP IMAGES/IR.1 MYDATA/IMAGES.1234 SIZE=ALL

o remap the VIS image into the projection of the IR image matching the
  resolution of the IR image:

  IMGDISP IMAGES/VIS.1 MYDATA/IMAGES.1234 MAG=-2

The remapped version of the VIS image will have pixels that are both
co-located with the pixels from the IR image.

If you then plan to display the remapped image for general view, you will
want to use IMGCHA to change the DAY, TIME, band, memo, etc. in the
remapped copy.

>Jason Allard
>Department of Geography
>The Pennsylvania State University
>University Park  PA  16802

Tom Yoksas