A study assessed the water quality status using a few parameters such as Chlorophyll a, BOD, COD, TSS and etc to determine the pollution level of water bodies using remote sensing techniques. Usually, such studies carried out in-situ sampling and laboratory-based analysis apart from the RS analysis. So is it compulsory or why do in-situ sampling and laboratory-based analysis required for such studies?
Please explain this...
It actually depends on some study areas where a lot of hydrodynamical changes occurred e.g., huge sediment discharge, strong seasonal variations, strong upwelling regions. If the conditions are so, then it is always good to recheck your remote-sensing products such as Chl-a, CDOM, TSS, etc. with the in-situ products. However, that is not compulsory because the remote-sensing methods also depend on some robust algorithms which are evaluated for time. If the remote sensing products are evaluated/validated before then you can definitely use those products for that area without in-situ measurements based on the validation results. From my views, some remotely sensed products like BOD & COD would result in unnatural or misleading values.
It actually depends on some study areas where a lot of hydrodynamical changes occurred e.g., huge sediment discharge, strong seasonal variations, strong upwelling regions. If the conditions are so, then it is always good to recheck your remote-sensing products such as Chl-a, CDOM, TSS, etc. with the in-situ products. However, that is not compulsory because the remote-sensing methods also depend on some robust algorithms which are evaluated for time. If the remote sensing products are evaluated/validated before then you can definitely use those products for that area without in-situ measurements based on the validation results. From my views, some remotely sensed products like BOD & COD would result in unnatural or misleading values.
It is extremely important to validate and callibrate de RS data with analytical determinations conducted in the lab. Remote sensing techniques have experienced a great development in recent years, but obviously they don't have the accuracy of a precise laboratory analyses by e.g. spectrometric or chromatographic techniques. This is especially critical for parameters like BOD or COD which must be chemically determined. Only with a good validation of your RS data (based on your lab results), which is usually site-specific, will you be able to be confident and rely on your RS surveys.
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