1. A method comprising: obtaining access to at least one of call data records, location update events, and control events between mobile telephone infrastructure and mobile phones for a plurality of mobile telephony users, said at least one of call data records, location update events, and control events between mobile telephone infrastructure and mobile phones comprising location-time sequences; for each of said mobile telephony users, segmenting corresponding ones of said location-time sequences into trips; for each of said mobile telephony users, using a home-work-school classification model to determine a home location and a work-school location, based on said trips; for each of said mobile telephony users, using a trip purpose classification model to assign each of said trips a purpose label, based at least on comparing at least one of a start location and an end location for each one of said trips to at least one of said home location and said work-school location determined using said home-work-school classification model; and aggregating said trips into purpose based origin-destination categories based at least on said purpose labels, time ranges of said location-time sequences, and said start and end locations.