I’m recently approaching the use of Cosmo Skymed images and I have doubts that I hope someone can solve me.
I’m using SNAP to pre-process images.
I start from CSK StripMap in HIMAGE mode, Level 1A product (Single-look Complex Slant - SCS).
- Do I need to correct images before coregistration? If yes, what filters are suggested for CSK?
For coregistration, see the tool below in the image:
I need to set the parameters, can someone give me information?
- Cross-correlation: coars window width, height and coherence threshold optimal for CSK?
- Cross-correlation: is coherence based registration useful?
- What further corrections or filters are suggested a posteriori and with what parameters for CSK?
- Topo phase removal?
- Goldstein filtering FFT Size? Goldstein filtering Window Size?
I also read that it would be better to use the ‘DEM Assisted Coregistration’ tool instead of the ‘coregistration’ tool. Has anyone tried it and had better results?
thanks in advance for any help
First of all, there is no true or false configuration of parameters such as filter sizes or coregistration windows. These can be adjusted in case you are not happy with your result. For example:
- If the coregistration did not find suffient GPCs, increase the windows size of the coregistration, if the quality of the coregistration (RMSE) is too bad, reduce it.
- If the interferogram is too noisy after filtering, select a larger Goldstein filter size, if the filter is too agressive, reduce the size.
- If you experience filtering artefacts (DEM generation with Sentinel-1 - Workflow and challenges last page), reduce the FFT exponent.
No image enhancement should be undertaken before coregistration, you can use the images as they are.
Multi-looking can increase the quality of the interferogram, but it is not mandatory and it reduces the spatial resolution. Yet, it can prevent unwrapping errors for noisy interferograms.
If you want to create a DEM, you do not remove the topographic phase.
If you want to detect displacement, you remove the topographic phase.
Please also have a look at these two tutorials where also stripmap modes are used: