Transition detection

An apparatus implementing steps stored in non-transient memory for determining a location and/or time of one or more transitions on a map stored in the non-transient memory, made by a set of mobile computing devices, from a first zone to a second zone, the apparatus comprising:

• a transition detector comprising processing circuitry implementing the steps stored in the non-transient memory and arranged to:
• obtain trajectory data representing a plurality of trajectories collected from one or more mobile computing devices, at least some of the trajectories passing through the first zone and/or the second zone;
• process the plurality of trajectories to identify transitions by:
• determining a pose graph of the plurality of trajectories located with reference to each other by identifying loop closures and relative motion constraints;
• positioning the pose graph in a frame of reference defined relative to the map by applying a transform of the pose graph, wherein at least part of at least some of the trajectories are positioned in the frame of reference defined relative to the map based on correspondence with other trajectories;
• and
• processing the plurality of trajectories positioned in the frame of reference defined relative to the map to determine the location and/or time of transitions from first zones of the map to second zones of the map by identifying clusters of trajectories in the pose graph, wherein the processing of the plurality of trajectories includes
• prior to generating the pose graph, removing trajectories or segments of trajectories having unreliable motion constraints,
• removing trajectories or segments of trajectories that are highly distorted by the process of forming the pose graph, and
• removing trajectories or segments of trajectories not having sufficient loop closures.

A non-transient computer-readable medium containing instructions which, when run on a system including processing circuitry, cause that system to:

• obtain trajectory data representing a plurality of trajectories collected from one or more mobile computing devices, at least some of the trajectories passing through a first zone on a map and/or a second zone on the map, the map being stored in non-transient memory;
• process the plurality of trajectories to identify transitions by:
• determining a pose graph of the plurality of trajectories located with reference to each other by identifying loop closures and relative motion constraints;
• positioning the pose graph in a frame of reference defined relative to the map by applying a transform of the pose graph, wherein at least part of at least some of the trajectories are positioned in the frame of reference defined relative to the map based on correspondence with other trajectories;
• and
• processing the plurality of trajectories positioned in the frame of reference defined relative to the map to determine the location and/or time of transitions from first zones of the map to second zones of the map by identifying clusters of trajectories in the pose graph, wherein the processing of the plurality of trajectories includes
• prior to generating the pose graph, removing trajectories or segments of trajectories having unreliable motion constraints,
• removing trajectories or segments of trajectories that are highly distorted by the process of forming the pose graph, and
• removing trajectories or segments of trajectories not having sufficient loop closures.