First of all, thank you very much to ESA for all it has done with this Forum.
Im a student of Telecommunications at Canary Islands and Im just finishing my studies, making a Final Project studyng the capabilites of SAR Sentinel-1 for land classification.
Last day (23 October) a village of Canary Islands suffered the worst rainning event of the last years…110 litres/square metre (2 hours). The rain did a lot of damage to a little part of the coast of the Island of Gran Canaria. The main thing here is that, Sentinel-1 just made one SAR capture at the moment of the event (Coincidence!). An IW product.
So I want to know if it is possible to determine the areas with water with this data. I have read that it is better to have a quad pol product, but these ones are dual polarisation only. So, before starting making tests…do you recommend me some steps for water/soil detection on land with this data?
Im going to try with Polarimetric Decomposition, as it says on tutorials…but they are thought for Quad Polarisations…
The exact product I have got is this: S1A_IW_GRDH_1SDV_20151023T190457_20151023T190526_008284_00BACF_DFB1 (available also on RAW or SLC)
Thank you very much in advance, it would be great to have results for this weather event in which goverment has declared a local emegency situation.
Sentinel-1 has only dual polarization capabilities, and over-land, usually, you will find products in
VH) as is the case with your product or in vertical polarization (
The flood (or water) tend to appear black on
SAR images, if the area is
rural (this could be the case for a
village) and is totally
submerged. In this case, you could already locate the flood visually and try to find a
pre-flood image (acquired in non-flooded situation) and perform a
change detection between the two (the difference between the two images for example). If you cannot find a
pre-flood image, you could choose a manual threshold (just to have an idea…).
Obviously, before applying the flood detection, your image need to be calibrated (see
Radiometric Calibration), and potentially speckle-filtered (see
Adaptive filters : Lee, Frost, Gamma)/ terrain corrected (using
Thank you very much “hakim” I will try! Well this was not exactly a village, (excuse my error) its near the beaches of the town of “Telde”.
I will try to process it! I have already calibrated them.
Flooding can be detected when the flooded scene is compared with a pre-flood scene or scenes. Try creating ratio-images between a pre-flood and flooded scene and see if the flooded area stands out.
Hi hakim, I have a quastion about flood monitoring by sar images, I want to know why we use GRD format instead of SLC one? you know better that we have both phase and amplitude information in slc products, (amplitude=square(i^2+q^2). Am i right? so I am confused know and pls explain the reason to me. thanks
Hi @zahra0729, as far as I know, the only difference between a GRD and a SLC product is that the GRD one has squared resolution cells and has been multilooked to reduce the speckle. Check pages 8 and 9 in the following document about TerraSAR-X products.
A GRD product looses the phase information as well, and therefore there’s no way to apply InSAR techniques to it.