Map Assisted Inertial Navigation

A method of identifying a path taken by a pedestrian within an environment comprising the steps of:

• identifying states relating to positions associated with an image of the environment to provide a collection of states;
• identifying pairs of said identified states and determining whether each identified pair is close;
• for each pair of close states, determining a transition probability;
• for each pair of states determined not to be close, setting said transition probability to zero;
• defining possible event observations;
• for each pair of close states, determining an event probability;
• for a period of time and at time intervals, detecting a set of events;
• and
• computing an estimated sequence of the states based upon the transition probability and the event probability.

A location device for identifying the location of a pedestrian within an environment comprising:

• a processing unit for receiving and storing identified positions associated with an image of the environment, a collection of states, and potential event observations;
• a close state determiner in communication with said processing unit for receiving state information and for determining whether pairs of states are close;
• a transition probability calculator in communication with said processing unit for calculating a state transition probability for each said close pairs of states;
• a potential observation identifier in communication with said processing unit for determining a set of potential observations;
• an event probability calculator in communication with said processing unit for calculating an event probability for each potential observation and each state transition probability;
• an event detector in communication with said processing unit for detecting the occurrence of an event;
• and
• a state probability calculator in communication with said processing unit for computing state probabilities for each state based upon the transition probabilities and the event probabilities for each state.