I am trying to use Scanaerial in JOSM to locate water sources in my county. I was able to install all of the required Python modules and ExtTools and load the scanaerial plugin, but now when I run it, it just scans the WMS layer endlessly and never gives me any output, at least for the hour I have let it run on an acre sized area.. All the documentation is on the OSM Wiki and the files are at this GitHub repo. I am not sure what I am missing to make this plugin produce some output.
Scanaerial takes lots of time to get results. If the image is not uniform, then it takes more time. The results are also not as good i.e. it does not give boundaries at the right place.
Alternatively, you can digitize large area as smaller pieces and then dissolve the boundaries.