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20010330: BAR command and customized stretch tables

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  • Subject: 20010330: BAR command and customized stretch tables
  • Date: Fri, 30 Mar 2001 16:36:18 -0700
>From: "Alliss, Randall J." <address@hidden>
>Organization: TASC
>Keywords: 200103302035.f2UKZCL21718 McIDAS-X BAR stretcy

Randy,

>Do you know the answer to this question?
>
>I am performing the following command.
>
>IMGDISP WEST/CONUS BAND=4 STA=DEN ;BAR
>
>i want the bar command to give me the temperature of the scene (200k - 320k)
>and not 0 - 255.
>
>is there a way to do this?

Yes.  I do this by defining a stretch table that has the appropriate
mapping of brightness to temperature and then tell BAR to use it in the
display:

SU TABLE IRTEMP
BREAKPOINTS STORED IN TABLE : IRTEMP.ST
INPUT       OUTPUT
-----       ------
 163           255
 241.9999      177
 242           176
 330           0
CALIBRATION TYPE  : GVAR
CALIBRATION UNITS : TEMP
BAND NUMBER       : -1
INTERPOLATION TYPE: LIN
SU: DONE

The stretch table values can then be used either directly or indirectly:

directly: tell BAR to use the stretch

IMGDISP WEST/CONUS BAND=4 STA=DEN; BAR SU=IRTEMP

indirectly: load the image using the stretch and then run BAR

The ability to define custom stretch tables allows one to generate labels
for displays via BAR that would ordinarily not be possible.

IMGDISP WEST/CONUS BAND=4 STA=DEN SU=IRTEMP; BAR

The nice thing about being able to tell BAR to use a particular stretch
table is that you can label your image in unusual ways.  For instance,
we generate composite images of IR and topography and then label the
image using a special stretch that indicates the temperatures of the
cloud.  An example of this can be seen in:

Welcome to the Unidata McIDAS Demonstration Machine
http://mcdemo.unidata.ucar.edu/

  Latest GOES-East Infrared/Topography Composite image 
  http://mcdemo.unidata.ucar.edu/images/GETOPO.GIF
  
>thanks,

Later...

Tom