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

Abstract: A computer implemented method of aligning a plurality of map segments having a local reference frame to a reference map having a global reference frame, each map segment overlapping a portion of the area represented by the reference map, the method comprising: for each map segment, independently generating one or more candidate alignments, aligning the map segment to the reference map; for each candidate alignment evaluating a cost function representing the likelihood that the candidate alignment is correct; based on the candidate alignments and associated cost functions, generating one or more candidate solutions, each candidate solution comprising a single candidate alignment for each map segment; for each candidate solution, evaluating a cost function based on at least the cost functions for each candidate alignment included in the candidate solution; and based on evaluation of the cost functions, determining alignment of the plurality of map segments.