One embodiment is directed to determining a location of a mobile device associated with an occupant within an indoor area using one or more images captured by at least one camera of the mobile device and a digital three-dimensional model of the indoor area. Information about the location of the mobile device is communicated to an emergency responder. Another embodiment is directed to determining the locations of each mobile device associated with each occupant within an indoor area using one or more images captured using at least one camera of the mobile device, storing each determined location along with an associated time stamp, and using at least some of the stored locations and time stamps in performing contact tracing. Other embodiments are disclosed.