[johnwalkr]

GPS-denied navigation is the search term. It works well enough for driving through a tunnel, because eventually you get a known location to correct previous estimates. For a fully-indoor environment it's very difficult to get good results and the technique depends on the use-case.

"Indoor GPS" using bluetooth beacons is technically possible but the space is filled with proprietary protocols/apps that try to make money by serving ads. It unfortunately doesn't seem to be evolving into a more useful extension of google maps.