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modis_user

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About modis_user

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  1. 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: 10 VI usefulness: 0111 Aerosol 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?
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