The waterbody I am studying is approximately 20 sq km. Its water levels differ seasonally and according to the specific location. Just wanted to know if there's a possibility to measure depth of waterbody at various points through GIS. Thank you!
A mountain reservoir, wet depression on a playa, riverine oxbow, etc. all would have different strategies, so actually mentioning or providing the area of interest extents would give a higher probability of a meaningful answer, including other data sources than Sentinel, or combined with something like a Sentinel time series. Also, there are many different sensors with their related characteristics on the various Sentinel satellites which have collected data over decades. SAR, for instance https://sentiwiki.copernicus.eu/web/s1-applications
In general for most cases Sentinel itself isn't going to provide bathymetric data, but INRE:"... through GIS" allows for fusing other data sources. This would entail knowing what the expectation is in terms of resolution, horizontal and vertical precision.
Normalized Difference Water Index (NDWI):
NDWI=Green−NIRGreen+NIRNDWI=Green+NIRGreen−NIR
where, Green is the reflectance in the green band, and NIR is the reflectance in the near-infrared band.
Modified NDWI (MNDWI):
MNDWI=Green−SWIRGreen+SWIRMNDWI=Green+SWIRGreen−SWIR
where SWIR is the reflectance in the shortwave infrared band.Empirical
Depth Estimation Model:
Depth=a+b⋅ln(Reflectance)
where a and b are coefficients determined through calibration, and Reflectance is the reflectance value from the satellite imagery.
Yes with a big “IF”. Here are the qualifiers to calculate volume of a waterbody from satellite data.
1. If your waterbody area was in a drought at any point in time after 2015 and was completely void of water.
2. If you have access to consistent water levels measurements at regular intervals of this waterbody since 2015. (ground truth)
IF 1 and 2 are true. Then with the satellite data you can create shoreline outlines or polygons over the same time periods and use water measured levels of your waterbody to calculate slopes of waterbody outlines over time and volume totals of waterbody. Your baseline would be an empty (drought) waterbody. Your accuracy would be limited by 10 meter satellite resolution, frequency of satellite passes, and water level interval measurements. In a nutshell you would be creating your own bathymetry and or volume of your waterbody temporaly.
If you don’t have “1” you can estimate bottom of your waterbody from your smallest shoreline polygon and projected slope to a point but this will reduce your accuracy.
If you don’t have “2” you can still estimate volume from the temporal slopes of your polygons but without ground truthing it will be less accurate.
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