When users are at known underground locations, such as tube stations they often do not have a GPS signal, as the radio waves from the satellites required cannot penetrate the earth, this RFC suggests providing GPS locations over WiFI using remote IP detection for a server to respond with the correct name of clients location and the clients GPS location.
The Java application here will look at a connection request's IP address and from there return a latitude and longitude plus name for that location. Thereby enabling mobile devcies who cannot lock a GPS satellite location to know where they are.
It requires the IP address to be forwarded to it by the web server, in the running case Nginx.
This protocol has been submitted to the Internet task force and will hopefully become a standard.
Video demonstration here
Rob Brew (email@example.com).