I'm having trouble interpreting some data I've loaded into a PostGIS database. I scraped rasters from here and converted to sql files using raster2pgsql. I'm now using PostGIS's special functions to query the database, to return rainfall data from a particular point. However, it seems to be that whatever I get returned is in the range 0 to 255. Some of the points only have values of 255, for any day. I am guessing that this is something to do with 8-bit colour graphics having a range from 0-255. Does anyone have any idea of how to convert what I have to the actual rainfall value? I can't find any kind of value to rainfall mapping system on the site itself, except an Adobe Color Table file -- is this what I need?
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1You scraped rasters... but which file? It seems as if you have downloaded an RGB image, with three colour bands with values 0-255.– alphabetasoupCommented Jan 14, 2016 at 22:25
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I scraped the GeoTIFFS for each file– lin_bugCommented Jan 15, 2016 at 2:39
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1 Answer
It seems you can't download the original rainfall data, and all data available can only be used for comparing cells in a given image or detecting trends for specific regions between data sets.
In "standard" data types (as they call them) such as JPEG and PNG, "Dark blue areas show where a lot of rain has fallen. Pale green to turquoise show increasing amounts of rainfall". The data is scaled to a range of 0-255, but these are not actual rainfall values.
In addition, as mentioned here, other formats such as CSV are available, but these are also scaled and do not represent real values. NEO claim they can assist you in identifying the data source, so perhaps you should contact them.
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An update for anyone else reading this: the estimated rainfall data in mm are available, from the CSV in Excel format and Floating point GeoTIFF files. However, as explained in the link Nir gave, these have been rescaled.– lin_bugCommented Jan 19, 2016 at 0:36