modis_user Posted April 12, 2016 Report Share Posted April 12, 2016 Hello, I'm currently working with the MODIS product MOD13Q1 (Vegetation Indices 16-Day L3 Global 250m) and I ran into some difficulties with the interpretation of the quality assessment information. I already posted my question on stackexchange ( http://gis.stackexchange.com/questions/171792/how-to-correctly-parse-modis-qa-layers ), but got no answers. Maybe anybody here has an idea? If I receive an answer here, I will update the question on stackexchange (and vice-versa). Here's the text of the question (identical to stackexchange): I'd like to correctly parse the MOD13Q1 VI Quality layer (see Table 2 in "layers" here). For this, I'm trying to follow Example 1 from this tutorial (page 10). I'll illustrate my problem with a pixel value of "VI Quality" from my real data set: 35038 First, I transform it to the binary value 1000100011011110. Then, I separate this binary value into different bit words (from right to left) according to Table 2: 1 0 001 0 0 0 11 0111 10 Following Example 1 ("Please bear in mind that the binary bit-string is parsed from right to left, and the individual bits within a bit-word are read from left to right."), I would then assume that I'd get the following bit words for the different categories: MODLAND_QA: 10VI usefulness: 0111Aerosol quantity: 11... and so on However, the problem is that the value 0111 doesn't exist in Table 2. I guess that there are two possible explanations for this: I made a mistake trying to apply the tutorial. In that case I'd be very thankful if somebody could point me to the right direction. I applied the tutorial correctly, but Table 2 is incorrect or incomplete. Could anybody confirm if this might really be the case, and if yes, where to find information about missing values? Quote Link to comment Share on other sites More sharing options...
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