Determining the geographic location of a portable electronic device

A method, performed in a radio communications network, of determining the geographic location of a portable electronic device, comprising the steps of:

• transmitting a radio signal from a first network transmitter,
• receiving, in the network, a measurement signal from the portable electronic device, which measurement signal comprises, for the transmitted radio signal,
• i) a plurality of data samples obtained in the electronic device from the transmitted radio signal at different time points during a measurement period during which movement of the portable electronic device occurs, the data samples are taken with a sample period controlled to target a predetermined distance between locations of measurement points at which the data samples are obtained based on a determined speed of movement of the portable electronic device during the measurement period, wherein the predetermined distance is selected to be less than one wavelength of the transmitted radio signal, and
• ii) local position data associated to each data sample obtained from a local positioning unit in the electronic device;
• determining, in the network, a direction measurement between the electronic device and the first network transmitter based on said data samples and said local position data associated to each data sample;
• obtaining geographic location data for the first network transmitter;
• and
• identifying geographic location data of the portable electronic device based on the direction measurement and the geographic location data for the first network transmitter.