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20021121: Avoiding possible IMGPROBE confusion

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  • Subject: 20021121: Avoiding possible IMGPROBE confusion
  • Date: Thu, 21 Nov 2002 12:37:12 -0700
  • >from: Jay Heinzelman <address@hidden>
  • >keywords: <address@hidden>
  • >organization: UCAR/Unidata
Hello McIDAS Users-

We have had some confusion from users on how IMGPROBE positions the BOX
for statistics calculations when using the non-interactive mode (MODE=N).

When using LINELE=, STATION=, or LATLON=, the BOX is positioned
according to the defaults in the PLACE= keyword.  If LINELE= is used,
the LINELE values by default (PLACE=ULEFT) define the upper left corner
of the BOX in which the statistics are calculated.  If STATION= or
LATLON= are used, the station or lat/lon pair by default (PLACE=CENTER)
define the center point of the BOX in which the statistics are
calculated.  This behavior is consistent with the use of PLACE= in the
other IMG* commands.

For example, we had a user who had a few years of McIDAS experience and
wasn't aware of the PLACE= keyword.  He was using LINELE= with MODE=N 
and DATASET= within scripts.  He thought that the statistics where 
calculated with the LINELE= coordinates at the center of a box, not the 
upper left corner default.  Notice the different output values when 
PLACE=CENTER is added in this example:

IMGPROBE STAT BOX RAD MODE=N DATASET=A.5512 BAND=4 SIZE=51 51 
LINELE=3500 4500 I

Name:A.5512
Calb Pixels   Minimum Maximum   Mean   Stn. Dev.
---- -------- ------- ------- ------- -----------
RAD   2601    -0.322   0.443   0.022   0.124
IMGPROBE: Done


IMGPROBE STAT BOX RAD MODE=N DATASET=A.5512 BAND=4 SIZE=51 51 
LINELE=3500 4500 I PLACE=CENTER

Name:A.5512
Calb Pixels   Minimum Maximum   Mean   Stn. Dev.
---- -------- ------- ------- ------- -----------
RAD   2601    -0.029   0.443   0.002   0.119
IMGPROBE: Done


Also, this applies to when you are using MODE=N with a displayed image 
as well as the DATASET= keyword.

I hope this is informative for everyone.  The IMGPROBE help section is 
being updated for the next upgrade to better alert users to this 
behavior.  Please let us know if you have any questions or comments.

Thanks,
Jay Heinzelman
McIDAS User Services
address@hidden


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