STEP-BASED POSITIONING

In a positioning system () for estimating the position of a mobile device (), a processing system () receives external-range data, representative of a range between the mobile device and an external unit (), and acceleration data representative of acceleration of the mobile device due to its movement as it is carried by a person (). The acceleration data is processed in a step-detection algorithm to determine step-distance data representative of a time series of step-data-based distances travelled by the mobile device, and step-distance data is processed to determine a step-data-based position estimate for the mobile device. A position estimate for the mobile device is determined by solving an optimisation problem comprising a first cost term based on distance to positions located at said range from the external unit, and a second cost term based on distance to the step-data-based position estimate or to positions located at a step-data-based distance from said step-data-based position estimate.