Hello everyone, I need some help.
I want to conduct land masking using shp file on S-1 SLC images.
So I imported one ESRI vector file, but it has several polygons, and it is larger than SLC image.
First, when I go to the Land/Sea Mask, only one vector(one polygon) can be chosen.
How can I use several polygons for land masking?
Second, land masking is not working because of the larger size of shp file.
I couldn’t find how to clip shp file into same as S-1 image.
Actually, the same shp file was resized(clipped) automatically when I opened it on another GRD image.
As you can see in the image above, the left side of shp file was also clipped automatically according to SLC image.
I wonder what is the difference and how to solve it.
Finally I want to do land masking with that shp file.
when you are loading the vector you are asked if you want to split the polygongs according to an attribute
if you select “No” here, all polygons are treated as one geometry. I don’t think that it should make problems when the shapefile is larger, because once you load vectors, SNAP creates a pixel mask of these areas which covers the size of the currently loaded raster.
Try to save your product after you imported it (File > Save Product), maybe open it again. Have a look at the vector extent (should now be there under “Masks”). If it is larger than your raster, maybe the actual raster is larger than what is displayed by the data and you have to make a spatial subset first to get rid of the right part.
Thanks a lot for your kindness. The merging problem has been solved, but the size problem remains.
I guess it happened because the SLC has 3 swaths.
Subset was also impossible because of the different size between bands(swaths).
I have another question.
The vector layer can be overlaid on S-1 SLC original data(.zip), but it is impossible to overlay on BEAM-DIMAP data(.dim), even though they are exactly same except the format.
The import button is not active on any bands.
Also, actually the vector has some offset from the SLC original data.
(The vector matched very well with GRD data.)
How can I put the vector layer on dim data with exactly location?
use the TOPS Split operator before you import the vector to reduce the SLC data to one single swath.
it will be active if you select the name of the product in the Product Explorer instead of clicking on single bands. But as I said, reduce the swaths of your SLC product in a first step.
I really appreciate your help!
After TOPS Split, the size problem has been solved.
But there remains one small problem.
Like the above image, there is no more horizontal offset, but you can see some vertical offset.
This phenomena occur in every swath.
Do you think what did cause it and how can I fix?
And, there are some different questions about S-1.
Do you know how to get the sensor effective velocity of each image? (or satellite and ground velocity)
In some Sentinel documents, there is a calculation “Ve=sqrt(Vs*Vg)”, but I have no idea what and where each values are. (I looked at annotation xml files of original zip data.)
Also, the reason I use SLC than GRD is that I want to calculate Doppler frequency from images directly.
I usually use MATLAB for image processing.
So I converted Sentinel original data to ‘img’ file using SNAP, and then loads them into MATLAB.
Then I made deramped SLC, after, estimated Doppler frequency of each swath and each burst.
I wonder if 10 bursts can be combined into one frequency domain.
(I think combination in swaths is difficult because of different parameters between swaths. Is it right?)
Finally, I want to see the Doppler frequency of the IW full debursted image. (if it is possible)
Even if the annotation file contains information about Doppler Centroid, I want to extract directly from images.
I hope you to reply if you can.
for a good overlay, you need to pre-process the data (TOPS Deburst and Range Doppler Terrain Correction). The SLC data is still in slant geometry and the shapefile is just coarsely draped of the image. It will be more precise once you geocoded it.
Is there a specific reason why you use SLC instead of GRD? Especially if you turn it into a GRD anyway.
I don’t know the one on the velocity and the Doppler frequency, maybe this was already discussed in here. You might want to have a look in the search function of this forum.
Thank you very much.
I need to preserve phase information, that is the reason I use SLC instead of GRD.
About velocity, I would look at more this forum.
alright, then you have no choice, I see.
As I said above,
I need to calculate deramped phase of each burst to get Doppler frequency domain of S-1 SLC data.
However, if I did preprocessing like deburst and range Doppler correction, I cannot extract deramped phase, because the phase deramped for every bursts.
Do you have any idea to solve the vertical offset issue without deburst?
Can I get deramped phase of debursted image(full image)?