[IDV #CHO-427775]: Colors on Water Vapor Imagery

Hi Greg-

> Full Name: Greg Fishel
> Email Address: address@hidden
> Organization: WRAL-TV
> Package Version: 2.6u2
> Operating System: Windows XP Professional
> Hardware:
> Description of problem:
> 
> This is a bit off topic, but I am hoping someone can steer me in the
> right direction. I work at WRAL-TV in Raleigh, and we show Water Vapor
> Imagery with 256 levels of color. Unfortunately, no one at our vendor
> has been able to give me a straight answer as to what temperatures
> correspond to those 256 color pots. After much research, I have learned
> that the GVAR 8 bit data has two different slopes to it, while the GINI
> data is linear and narrows the temperature range to -10 to -60, and
> spreads it out over the 256 colors, thus increasing the resolution, but
> sacrificing the extremes on either end. 

Can you provide me a reference on this?  If you compare a GINI
WV image with a corresponding AREA file, the brightness counts
(0-255) are the same (i.e.; the images look the same).  I'm comparing
the GINIWEST 8 km WV West CONUS with the RTIMAGES GOES-W 6.8 micron 
Water Vapor image.

Roger Weldon was nice enough to
> send me the specs for one of the color tables he uses with water vapor
> imagery (attached). When I apply those numbers to our graphics system,
> it looks nothing like it should. However, when I apply it in IDV, it
> looks very reasonable. That surprises me because I am using the
> GINIEAST dataset, and would have thought that Roger's colors would have
> failed the same way they did on our system. Does the IDV software
> account for the fact that the GINI data covers a narrower range of
> temps? All I want to accomplish here is to know what temperature
> corresponds to each of the 256 color pots, so I can replicate several
> other color pallettes in our system. Any help you ca

If he could sent you the McIDAS Enhancement Table (.ET), you can
load that into the Color Table Editor to save yourself some typing.
Also, if you could pass me a copy, it would save me some typing.
The values in the color table that he sent are brightness counts, 
not temperature.  Perhaps your graphics image is in temperature units
already (K), so the comparison is apples to oranges.  A way to
test this would be to change the Data Type in the Image chooser to
Temperature to get the WV image as temperatures and apply the color
table.  My guess is that it would look like your graphics image with
lots of reds.  

> By the way, the other two attachments are Roger's numbers applied in
> IDV and to our graphics system-quite a difference!

Again, I think one is brightness and the other temperature.  McIDAS
uses brightnesses for the enhancement table values.

Don Murray

Ticket Details
===================
Ticket ID: CHO-427775
Department: Support IDV
Priority: Normal
Status: Open