[McIDAS #VBD-592750]: retaining TEMP units with IMGOPER

Hi Owen,

I hope your holidays were as much fun as mine!

re:
> By now you have probably seen Matthew Lazarra's brand new Arctic
> Composite images. He's been wanting to obtain funding for these for a
> long time and had trouble getting NSF to listen, but as this year is the
> International Polar Year and as myself and many others really need the
> product for our aircraft missions over the Arctic in the spring, he was
> finally able to convince NSF.

Yes.  In fact, I wrote a letter of support for the production of the images
for Matthew's proposal, AND have been in touch with him about adding the
images to the UNIWISC datastream of the IDD.

> So I have wasted no time in producing some
> nice image loops of the product to get myself familiar with the cloud
> and ice features for NOAA's Alaska mission in April. You can see the
> products at:
> http://www.esrl.noaa.gov/csd/metproducts/polarcat/

Very nice!

> As always I like to use the full color spectrum when displaying IR
> images so that I can get as much info out of the images as possible. My
> idea is that I should be able to use IMGOPER to find the warmest pixels
> in all images over a one-week period which should filter out all clouds
> and give me the brightness temperature of the earth's surface. This
> should show me where the sea ice is located over the Arctic. A priority
> of the aircraft mission is to sample air over sea ice and open water to
> look for chemical differences.
> 
> As a test I issued the following command to find the warmest pixels over
> a one day period (8 images, every 3 hours). I specified UNIT=TEMP as I
> want to retain brightness temperature values.
> IMGOPER POLARCAT/ARC_COMP_IR.0 POLARCAT/ARC_COMP_IR.-1
> POLARCAT/ARC_COMP_IR.-2 POLARCAT/ARC_COMP_IR.-3 POLARCAT/ARC_COMP_IR.-4
> POLARCAT/ARC_COMP_IR.-5  POLARCAT/ARC_COMP_IR.-6
> POLARCAT/ARC_COMP_IR.-7  POLARCAT/SEA_SURF_IR.1 FORM=CMIN  1  1 MISS=1 1
> 1 1 1 1 1 1 UNIT=TEMP SIZE=ALL

Looks good.

> But when I plot the new image and scan it with IMGPROBE I find that the
> output is just RAW BRIT PROD and values for each of these 3 outputs are
> identical and range from 0 to 255.

This is expected.

> So my question is how do I get output in units of brightness temperature?

I would use the PRDUTIL command to add a calibration block to the output
image.  The other alternative since the resultant image values are unaltered
from the originals (i.e., not averages, etc.) is to fiddle with the output
image's directory (i.e., make it look like one of the input images).

Here is what I would do using PRDUTIL:

PRDUTIL LIST POLARCAT/SEA_SURF_IR.1
PRDUTIL DEL POLARCAT/SEA_SURF_IR.1
PRDUTIL ADD POLARCAT/SEA_SURF_IR.1 1 TEMP 163 242 255 177 K 0 0
PRDUTIL ADD POLARCAT/SEA_SURF_IR.1 2 TEMP 242 330 176 0 K 0 0

The values I used in the creation of the calibration block are
the standard ones for calibrated GOES images (which the ARCTIC
composites seem to use).  The are instantiated in the IRTEMP.ST
stretch table that I include in the Unidata McIDAS-X distribution:

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

> thanks!

No worries.  Please take a look at the above and give me your feedback.

Cheers,

Tom
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Ticket Details
===================
Ticket ID: VBD-592750
Department: Support McIDAS
Priority: Normal
Status: Closed