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, each of said trips comprising a start location and an end location extracted from said location-time sequences upon said segmentation; 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 between the start location and the end location a purpose label indicative of the purpose of the trips, based at least on comparing at least one of the start location and the 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.