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[Datastream #SXB-674928]: GOES East West imagery...



Hi Gilles,

I apologize for the slow response to your emails.  We are in the middle
of hosting the triennial Unidata User's Workshop, and the time I have
for attending to support inquiries has been limited...

re:
> me again, sorry,
> 
> I custom-made an inversed color table from the Gempak color table I
> normally use to enhance IR imagery (it is not perfect but it is OK)
> 
> If you know anyway a way to inverse the scale (if it is in IDV it is even
> better), that would be really appreciated,

In the IDV all you have to do is to invert the range that the enhancement
is mapping to.  This can be done by right clicking on a color bar for
an image that has been displayed and selecting Change Range, or you
can create a new color table from an existing one in the Color Table
Editor.

In the color table editor, simply swap the low and high data values in the 
Range entry boxes and then save the enhancement under a different name
whose name will remind you that the values have been inverted.


re:
> For time of operation and corresponding satellite number I gathered some
> information  so it should be fine (see attached screen shot for time of op)

OK.

Just to make sure that I am understanding your comment "so it should be fine":

Are you saying that you now have enough information to allow you to get
archived images from GOES-East and GOES-West datasets for the time
periods you are interested in?

re:
> I also tried to download data from the CLASS website (that allowed me to
> see which GOES number I should use),
> 
> I attached the imagery for a specific date in 2011 in McIDAS data format
> (at low resolution)

FYI: The image you downloaded from CLASS is 10-bit imagery.  The images that
are distributed in the Unidata-Wisconsin (IDD feedtype UNIWISC) datastream
are 8-bit.

re:
> Once uploaded in IDV, I noticed that the scale is inversed compared to what
> I normally download from adde.ucar.edu server

That is correct.  The color table is being applied to the range of values
in the image, and because the image is infrared, the higher values pixels
are warmer temperatures (higher pixel values -> more blackbody radiation
-> warmer).

re:
> I think I remember during a workshop I assisted at UNIDATA that you
> mentioned something about the scale in which satellite imagery comes as
> original format and how to inverse it but I cannot find it in my notes
> What is the way to inverse the scale? (or should I design a specific scale
> equivalent to the one I normally use in IDV (I am pretty sure there is a
> way...frustrating to not remember))

As I noted above, you can simply edit the color table (which I typically
refer to as an enhancement since that is called in McIDAS-X) and change
the low value of the range to what the high is and the high value to what
the low was.

re:
> I would not be surprised that the data in the UNIWISC IDD Datastream will
> come the same way than the CLASS data, so I think that I have to solve
> that detail anyway.

The default in the IDV is to recognize images that have had their
raw, 10-bit counts mapped into brightness values and automatically
flip the application of the enhancement.  This is so that the display
of cold cloud tops in IR imagery looks like clouds (meaning bright
white).

Please let me know if the above was understandable.

Cheers,

Tom
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Ticket Details
===================
Ticket ID: SXB-674928
Department: Support Datastream
Priority: Normal
Status: Closed