20021004: BAR command and using a stretch on a remapped NEXRCOMP image (cont.)

>From: "Paul L. Sirvatka" <address@hidden>
>Organization: College of DuPage
>Keywords: 200210041733.g94HXZ106826 McIDAS NEXRCOMP BAR IMGREMAP IMGCHA

Hi Paul,

I will restate the objective of your endeavor as I understand it, and
give you my approach.

You want to remap a NEXRCOMP 1 km national base reflectivity composite
radar image into the projection of some other image.  You want to suppress
echos in the remapped image that are less than 5 dBz.  Finally, you want
to put up a data bar that reflects the echos that are visible.

Here is my approach:

1) remap a NEXRCOMP/1KN0R-NAT composite base reflectivity image into a
   GOES-East projection (you have already done this, I just want to
   be complete):

IMGCOPY RTIMAGES/GE-IR MYDATA/IMAGES.1234 SIZE=ALL
IMGREMAP NEXRCOMP/1KN0R-NAT MYDATA/IMAGES.1234 SSIZE=ALL

2) display the remapped image

IMGDISP MYDATA/IMAGES.1234 EU=BREF24

   This will result in a display that still shows echos below 5 dBz.

3) create an enhancement that suppresses echos below 5 dBz.

EU MAKE 0 85 BLACK
EU SAVE MYBREF

   I came up with this by examining brighness levels in the displayed
   image.  It seemed that brightness levels of 85 and below represented
   the echos you do not want to show.

   After you have created the desired enhancement, you could load all
   succeeding images using it:

IMGDISP MYDATA/IMAGES.1234 EU=MYBREF

4) create a stretch table that correctly shows the relationship between
   echo that range from 5 to 75 dBz and brightness levels that range
   from 85 to 255:

SU INI MYBREF NIDS ECHO
SU MAKE MYBREF 5 75 85 255

5) use BAR to put up a data bar on the image:

BAR SU=MYBREF


Please let me know if this is not what you had in mind.


Tom