I would like to learn more on processing SAR images (general characteristics, pre-processing, filtering), in particular Sentinel-1, for crop monitoring (paddy rice in particular) in areas where optical imagery normally fail due to heavy cloud.
Is there any good training/resources to start?
Dr. Ian Woodhouse has a good interactive tutorial that accompanies his equally good entry-level book:
http://www.geos.ed.ac.uk/~ihw/hype/radar/intro2radar.html https://www.amazon.co.uk/dp/0415271231/ref=as_sl_pd_tf_lc?tag=iainwoodhome-21&camp=1406&creative=6394&linkCode=as1&creativeASIN=0415271231&adid=0KJQEAMVXN1W6XY27K78&&ref-refURL=http%3A%2F%2Fwww.geos.ed.ac.uk%2Fhomes%2Fihw%2Fbooks.html
The documentation for PolSARPro, an open source SAR polarimetry toolbox, is also quite informative:
https://earth.esa.int/web/polsarpro/documentation
Natural Resources Canada also hosts some good entry-level tutorials:
If you are new to SAR, SAR-EDU gives a great overview with a collection of tutorials/lectures.
SAR-EDU is a joint education initiave for Radar Remote Sensing, conducted and coordinated by Friedrich-Schiller University Jena and the German Aerospace Center and their goal is to provide knowledge about the basics, methods and applications of Radar Remote Sensing to users and scientists.
The SAR-EDU website set up by Friedrich-Schiller University Jena and the German Aerospace Center (DLR), provides lessons, talks, and tutorials (sample data included) for a range of radar remote sensing topics. Topics cover a broad range of processing & applications, from basic mathematics to general and application-specific image processing. Some units cover the use of programming (e.g. Python) and specific software (e.g. ESA's NEST). All of this is available for free, though registration is required.
There is a Biosphere category which includes a unit on crop type classification. If you don't find exactly what you need there I'm sure you will still find this to be a valuable resource.