Abstract: A computer implemented method (400) of determining a location of one or more transitions (5a-e) on a map and/or the time at which one or more transitions (5a-e) occurs, the one or more transitions (5a-e) made by a set of mobile computing devices (13a-c), from a first zone (2) to a second zone (4), the method (400) comprising: obtaining (402) trajectory data representing a plurality of trajectories (302 a, b) collected from one or more mobile computing devices (13 a-c), at least some of the trajectories (302 a, b) passing through the first zone (2) and/or the second zone (4); positioning (404) the trajectories (302 a, b) in a frame of reference defined relative to the map, wherein at least part of at least some of the trajectories (302 a, b) are positioned based on correspondence with other trajectories (302 a, b); and processing the plurality of trajectories (302 a, b) positioned in the frame of reference defined relative to the map to determine the location and/or time.

Abstract: A computer implemented method (400) of locating a plurality of mobile device trajectories (301) relative to each other and a map (1, 1?), the mobile device trajectories (301) comprising a time series of position nodes (303) joined by edges (305), the method (400) comprising: obtaining an input pose graph (311) comprising a plurality of mobile device trajectories (301) and a plurality of first constraints (309) defining the position and orientation of nodes (303) and edges (305) of the trajectories relative to each other; performing a non-linear optimisation process on the input pose graph (311) based on the first constraints (309), to reduce a cost function associated with the first constraints (309), the non-linear optimisation process providing a modified pose graph (313); extracting one or more sub-graphs from the modified pose graph (313), and for each sub-graph, individually processing the sub-graph to map match the nodes (303) and edges (305) of the sub-graph to features defined in the map (1,1?); and g