do you guys know if I need to calibrate (in sigma0 values) before or after applying the speckle filter?
I’ve been told that I cannot apply the filter in a image with sigma0 values. Is that true?
Anyway, do I need to calibrate it at all?
And, at last, when I calibrate, the sigma0 band comes in linear scale, right? I wanted them in dB scale, but it is not, since there is no negative value when I choose to see the pixel info.
Calibrate with Sigma 0 values
Speckle filter
Terrain Correction
Convert from linear to dB.
At the step 3, should I mark the box of apply radiometric normalization? Considering that my data is already in sigma 0…
when you have calibrated the data and you already have Sigma0 you don’t need to select the “radiometric normalization” in the Terrain Correction module.
Application of the orbit files is not mandatory but often improves the geometric accuracy of your product. It should be done at the very beginning.
Speckle filtering reduces noise-like patterns in your image.
Terrain correction reduces gemetric distortions due to the side-looking geometry of your system.
yes, you can do that later as well. Also it is not mandatory, it just stretches radar backscatter over a more usable range which have nearly a gaussian distribution.
Hi Iveci,
Your explaination is very useful.
I have another question for GRD product preprocessing. Since the sigma 0 is in intensity scaling, if Iwant to get the radiometrically calibrated value of amplitude, can I directly calculate the square root the sigma 0 values?
Hi, All radiometric measurements from detected SAR imagery (such as Sentinel-1 GRD products) should use intensity values and not amplitude. So radiometrically calibrated value of amplitude is not a physical quantity and it should not be used.
FYI, the only reason why detected products include amplitude values is so that the dynamic range of the processed SAR signal can fit into the 16bits of the product. If intensity values were included in the product, 32 bits would be required per pixel and so the product would be twice the size.
Hi valgur,
Thanks for the document.I have read the document, but when I want to select any particular value in the look up table how could I proceed…
Actually my reflector area lies in 6776 line ,12185 pixel no approx. N Grdh is having 16586 lines and 25867 pixels in each line so how to reach my line n pixel value.I ve verified the calibration vector list… nearest vectorlist line is 6716…I am really confused anyone pls help me in this regard…
If I need to locate based on azimuth time where will I get exact azimuth time of my target…
Thanks in advance