Could you please explain the following segment in the xml file from https://seadas.gsfc.nasa.gov/help/GptCookbook/gptCookbookMosaic.html
Not sure what condition_0 is and also <combine>OR</combine>.
Corresponding parameter file is also available after the xml file at the above link.
condition_0is an arbitrary name for the
qualityExpression, but it is helpful to use a descriptive name such as "valid_range" The Help documentation has many pages of information on Mosaic (under Raster/Geometry/Mosaic and the GPT Cookbook) that explains how a qualityExpression is used. The Raster/Geometry/Mosaic help includes a section for Conditions. To make sure you understand what the conditions do you should experiment in the GUI with your data (one product) and different conditions.
condition_0is an arbitrary name for the "qualityExpression". It is helpful to use a descriptive name such as "flags_masked" or "valid_range" The Help documentation has many pages of information on Mosaic (under Raster/Geometry/Mosaic and the GPT Cookbook) that explains how a "qualityExpression" is used. The Raster/Geometry/Mosaic help includes a help section for the "Variables & Conditions" tab. To make sure you understand what the conditions do you should experiment with your data in the GUI and different conditions. The GUI allows you to use the Expression editor, which can help avoid erros in entering expressions. Setting "Output" to "true" ("Outp." seems to be an abbreviation for "Output" -- maybe the tab wasn't wide enough for the full name) helps you determine how often a condition was triggered.
If something in Help documents is unclear please suggest how it can be improved.
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As previously noted in this thread, rhos_412 and other surface reflectances can in fact be negative, and for that matter could be greater than 1.0 as well. Cloud shadow and cloud tops are 2 possible instances in which this might occur. There could be other instances. The fill value (-32767.0) is another instance.
The likelihood that the float value rhos_412 precisely equals zero is extremely small. Most likely you want something like (rhos_412 > 0.0 && rhos_412 <= 1.0) instead of (rhos_412 != 0) in your expression. If you wish to retain the "official" range then you want (rhos_412 >= -0.05 && rhos_412 <= 1.0).