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Pancam Spectra
jmknapp
post Feb 19 2004, 10:10 PM
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Playing around with another way of dispalying the image info. Not sure how useful it is yet, but it does butcher colors in a unique way.

True color Spirit image (weighted composite of L3, L4, L5, L6 & L7):



Full Res

OK--each point of an image has a spectrum defined by its intensity in the L2, L3, L4, L5, L6 and L7 images. So if the 1 million point spectra (1024x1024) are analyzed into the best-fit 256 spectral classes (k-means clusters) and a somewhat arbitrary color applied to each class the following image is obtained:



Full Res

Yuk! Well, maybe after some tweaking this could be interesting. The idea is all points of the same color share more or less the same spectrum in the six filters used to make the image.


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djellison
post Feb 19 2004, 11:28 PM
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I'm not a programmer, so I have no idea how this could be done, but to me, it would make sense on a pixel by pixel basis to generate a wavelength vs intensity graph, and take from it, values for R, G, and B.

However - we dont know the exposure of each pancam filter, and the stretch done on board before transmission, or the treatment on the ground, so really any such calculation is invalid

Doug
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jmknapp
post Feb 20 2004, 01:34 PM
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Well "invalid" is relative, since in an absolute sense every representation is invalid.

The "true color" image above was weighted by the expected exposure times vs. wavelength for L3, L4, L5 , L6 and L7 (the five visual wavelengths available), so it's better (although maybe less visually interesting) than just putting the color planes together unweighted. Clearly it would be better still to get the actual exposure times, but that info is not available to my knowledge and probably won't be until they put the images in the Planetary Data System in up to 6 months' time.


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