Subset data download for OMHCHO V003 data

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GES DISC - mgreene
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Subset data download for OMHCHO V003 data

by GES DISC - mgreene » Thu Apr 09, 2020 12:42 pm America/New_York

I want to provide feedback about the subset data download for OMHCHO V003 data. In the data subset, almost all the variables are cropped, but the corner points of latitude and longitude (e.g. PixelCornerLatitudes and PixelCornerLongitudes) are not cropped. Hence, they have a different dimension size as compared to latitude and longitude. It would be nice to also have these two variables cropped.

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GES DISC - mgreene
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Re: Subset data download for OMHCHO V003 data

by GES DISC - mgreene » Thu Apr 09, 2020 12:46 pm America/New_York

The variables 'PixelCornerLatitudes' and 'PixelCornerLongitudes' contain the coordinates of the corners of each pixel. The corner locations fall on either side of the pixel centers, which are defined in the geolocation variables 'Longitude' and 'Latitude' having the dimensions nTimes and nXtrack. Extra elements are needed to define all four corners for each pixel, so the dimension sizes of the corner variables are (nTimes+1) and (nXtrack+1). Variables in the subset output files are cropped according to the mask, which is based on the nTimes and nXtrack dimension sizes. Because the dimension sizes of the PixelCorner variables do not match all the other variables in the file, they do not get cropped.

Note that this issue does not apply to all data products from OMI.

If you require cropped pixel corners, there is another product, OMPIXCOR (https://disc.gsfc.nasa.gov/datasets?key ... COR&page=1), that contains pixel corner information that will crop as you expect. Enter the same search criteria for OMPIXCOR that you entered for OMHCHO, and the cropped data for the two will correspond to one another.

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