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Hi Tejay,   Thanks for bringing this to our attention! There's definitely something odd going on with those two parameters in the SU file you referenced, and I agree with your initial assessment that the BD1900_2 values reported look like they're reporting BD1930, instead. I'll look into this in more detail, and report back here once I figure out what's going on.   John

Upon looking in this further, all BD1900_2 seems to be returning is BD1930:   The error between BD1900_2 as per the CRISM DPSIS documentation is this: But when I just return BD1930 instead:   Is anyone able to verify my suspicion. The next question is how is BD1900r2 really calculated as that one is going to be a lot hard to tease out?

Hi All, What I am seeking to do is to replicate/verify the calculation of the various bands contained within su164j MTRDR files and apply the same calculations to spectral data of minerals from a lab so I can compare like to like thereafter. I can replicate all of the MTRDR bands I have selected from the su164j file (with convincing accuracy) via the spectral data contained in the if164j file – except for BD1900_2 and BD1900r2 and thus the reason for my post. I am wondering if anyone else has tried to replicate the same and found an error with the specified formula? I have found an error in the CRISM DPSIS when trying to replicate other bands via cross referencing different sources… but this one I can’t resolve. I've detailed all my calculations: The formula From the CRISM DPSIS document:   The data From the file frt0000b385_07_su164j_mtr3.img and cell reference [580,595] I get BD1900_2 = -0.009848237. I am now going to try and replicate this result using the spectral data contained within frt0000b385_07_if164j_mtr3.img.   Kernel Width As I understand it, I need to retrieve the five closest wavelengths to 1850, 1930, 1985 and 2067, extract the reflectance values and calculate the median, this is as follows:   Calculating "a" and "b" values: The formula for this is: However, I could interpret this in 3 ways:| 1) Ideal - Stick strictly to the formula in the CRISM DPSIS document and use the wavelengths of 1850, 1930, 1985 and 2067; OR 2) Closest to Ideal - Use the wavelength closest to those ideal wavelengths, so for example instead of 1850 I would use 1848.95; OR 3) Median - Use the wavelength corresponding to where the median reflectance value come from in the case of R1850:5 that would be 1842.34. Calculating all 3 possibilities gives:   Calculating BD1900_2 Following the formula for BD1900_2 from there, with the 3 possibilities for the calculation of "a" and "b" gives:   Results discussion As per the file frt0000b385_07_su164j_mtr3.img at cell reference [580,595], the value of BD1900_2 is -0.009848237. Trying to calculate the same, but from first principals via the spectral data contained in the file frt0000b385_07_if164j_mtr3.img does not give the same result - not even the same sign... in fact for any cell there is a concerning difference between the BD1900_2 values in the su164j file and that calculated from the if164j. With other bands, I can pretty much reproduce nearly identical result (to 6-7 decimal places typically), which leads me to ask: - Is there a typo or something in the stated formula for BD1900_2 that is preventing me from replicating the same? Attached are my excel workings if someone can assist. Note: I am a Financial Math Masters student whose designated research project is identifying minerals on Mars via machine learning so if my lingo is not up to scratch, it's because just 5 weeks ago I didn't have any clue about spectral data! Thank you!! BD1900_2.xlsx

Okay, Many thanks! Yeah, I was looking at this slide from the CRISM workshop 2012, but couldn't find it in it (CRISM Post-TRR3 Processing and Products is available).

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