In order to create an algorithm for data processing, it is crucial to first introduce the notion of "the usual place of residence" for the person and "night-time population", which cannot be achieved based on the traditional data sources.
Due to the opportunities available to replace movements and live in multiple residences, the dynamics of the act of migration might no longer be quite so clear. When the person visits several locations, one needs to identify "home" based on the duration, e.g., the location where the majority of the time is spent. This means that the duration of stay defines the meaning and importance of different locations. Subsequently, it allows to distinguish the change of residence from other moves.
Another factor that would help to identify the meaning of location is the start and end times of trips. These indicators vary according to the visit type and this makes it possible to view the trips as related to either work or vacation. In the case of trips related to work, a clear workweek pattern is discernible such that the trips start most often on a Sunday or a Monday and end on a Thursday or a Friday. During the weekend, the people usually are visiting their second home or move for tourism reasons.
Tracing activities (incoming/outgoing calls and SMS, internet connections) of the person with the time linkage would subsequently help us to determine "home" (where the person spends most of the night-time and weekends) and "usual environment" in general (for example, working place, where the person spends most of the day-time during the weekdays, as many of cases show). For domestic subscribers, the usual environment can be defined with the precision of country of reference, region, municipality or some other geographical areas or administrative units. The level of detail used depends on the data available and the producers' needs. Eventually, the usual place of residence can be identified as the place where the person has spent most of the nights rather than relying on the data based on the frequency of communications.
As regards the outgoing calls, the following parameters have to be considered: a) the exact time of the call activity; b) the random ID number for the phone (not related to phone or card number); and c) the cell ID with the geographical coordinates of the antenna.