The geographical landscape of the UK and Ireland is scattered with mobile telephone masts. Each mast has one or more cells (shown in figure 1). In simple terms, when a mobile telephone is making/receiving a call or a text message it uses a cell to manage the connection.
Each cell has a unique number assigned to it known as the Cell ID. It is this unique cell number that the network providers store for each connection a telephone makes and receives on their network. The records containing this information are known as the Call Data (Detail) Records (CDRs for short). It is these CDRs that allow cell site analysis to be conducted.