Call Detail Records (CDRs) are routinely produced by mobile network operators (MNOs) for billing purposes.

Each time a subscriber makes or receives a call, sends or receives a text message, or uses mobile data (collectively referred to as “network events”), a new record is generated.

CDRs graph

Each record contains the type of network event and the subscriber’s identifier, as well as the time of the event and the cell site it was routed through.

The MNO stores these records in a database and may connect them with other information on the subscriber and their account, to inform their billing process. These data can be analysed to better understand how people move within a country.


Spatial and temporal resolutions

As CDR data record the cell tower a network event was routed through, and not the position of the subscriber’s device, the spatial resolution of the data is limited by the density of cell towers. Similarly, the temporal resolution of the data is determined by the frequency with which subscribers use their mobile devices which is affected by a range of factors.

These limitations and how they can be addressed are discussed further in the Strengths & Limitations of CDRs page:

Read more