Agree with @DevdattaTengshe at this point, there will not be enough people supporting a distinct RS site, and the same applies for GPS. However, RS and GPS do have their own specific questions and including those questions here in GIS SE might be inappropriate. I believe people who working with RS or GPS do not expect to find answers for their questions in GIS SE.
What's worth to mention is that in China, we have a term called "3S" which refers to (GIS, GPS, RS), and if there's some website related to all of these three, it's usually named as 3S blah blah. Would it be good to have a site called 3S SE which including questions in GIS, GPS and RS?
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