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[IDV #OEB-275527]: Plotting difference values between 2 geolocated images

Alan,

Once the images have been loaded, geolocate your data via
Formulas, Imagery, Geolocate an Image.

After you display or render the PNGs, save them in the data
cache. Click on the image link in the legend. This action will bring
forth the Displays tab in the Field Selector. Then go to File -->
Save --> Save Data in Cache. Do this for both images.

At this point, take the difference of the cached data. That will
generate the contour plot. Note this will only work for image data
that are in a lat/lon projection.

Best,

Unidata IDV Support

> Full Name: Alan Bol
> Email Address: address@hidden
> Organization: COMET
> Package Version: 4.1 build date:2013-08-02 18:38 UTC
> Operating System: Windows 7
> Hardware: Java: home: C:\Program Files\IDV_4.1\jre version: 1.6.0_43 
> j3d:1.5.2 fcs (build4)
> Description of problem: Hi there,
> I have two color-shaded geolocated images (256 gray scale). They happen to 
> show mslp, but it could be anything. I would like to find the difference 
> between the two images and generate a contour plot of that difference. I've 
> tried a simple difference of the two images, and I've tried a simple 
> difference of "any field". Neither method generates a contour plot.
> 
> A little background: we've been tasked with validation of AWIPS-2. 
> Unfortunately, for derived fields, the only 'data' we get are images - no 
> data files. I'm exploring use to IDV to quantitatively compare 2 image files. 
> This is my first try. For this test, I generated 2 images of MSPL analysis 
> over the US (GFS and NAM), plotted with a grayscale. I also generated a plot 
> of the difference between the two analyses. I capured the MSLP images and 
> loaded them into IDV as geolocated images. So far, so good. However, when I 
> try to take the difference between teh images, something goes wrong. No 
> contour plots are generated. I can generate a "Value Plot" but the numbers 
> don't look right. However, when I probe the data (middle mouse button) the 
> values from the imported images look right (corrected for the fact that 
> originally plotted a range of 100mb (952 to 1052) over 256 shades of gray).
> 
> So, How do I plot the differrence in gray-scale values between 2 images? Any 
> ideas?
> I'll attach the two images I captured along with the bundle.  I can pop over 
> to your office and show you if that helps.
> Thanks!
> alan
> 
> 


Ticket Details
===================
Ticket ID: OEB-275527
Department: Support IDV
Priority: Normal
Status: Closed