In geographic locations, GPS or triangularization with cellular antennas is almost a "problem solved," even with features and facilities available in the API of the main operating systems for mobile devices such as Android and iOS.
But how is the "geographic" location (between quotation marks here because it is not quite a location on the globe) made of mobile devices indoors, such as a large ballroom? Is there any standardized or easy-to-use solution for this?
PS: In some comments commercial tools have been indicated that do this (and this information was certainly very welcome!), but I would like to have an answer detailing the operation of one (or more!) of these solutions because I believe that this would be useful also for the whole community of the SOPT.