Our prior research in [6] has a different focus; it considers
extracting the semantic location from outdoor positioning systems.
Likewise, [20] learns and recognizes the places a mobile user
visited by observing the Wi-Fi and GSM radio fingerprints. This
work does not consider Wi-Fi or GSM information. Instead, we
consider GPS and transportation network data. Transportation
network data is available freely to the public in many cities [25, 26,
28].