Wireless handheld portable navigation system and method for visually impaired pedestrians
This invention relates to a system for orienting and guiding visually impaired pedestrians. The system combines a Global Positioning System (GPS) receiver to a dead reckoning unit that compensates for GPS imprecision and loss of signal. The system is highly portable: it is based on a handheld portable computing platform that communicates wirelessly with a self-powered strap containing the GPS receiver and the dead reckoning unit. The system also uses wireless protocols to receive additional orientation information from a remote location server or operator accessible through the internet. Additionally, a positioning algorithm for mapping the user near a street intersection is provided.
1 . A method for a portable positioning device to accurately determine the location of a user travelling near a road intersection where a plurality of road segments meet, said method comprising the steps of:
a) periodically obtaining positioning data for said user from a satellite-based positioning system;
b) mapping each of said positioning data to a mapped point on a digital road map including said road segments; and
c) when the user gets within a predetermined distance of the road intersection:
i. associating a candidate road segment from said plurality of road segments with each mapped point;
ii. assigning a weight to each of said mapped points;
iii. electing one of said candidate road segments upon the weights of all the mapped points associated therewith adding up to a predetermined value, thereby accurately locating the user on said elected road segment.
2 . The method according to claim 1 , wherein step a) comprises obtaining said positioning data from a satellite system.
3 . The method according to claim 2 , wherein said satellite system is a GPS.
4 . The method according to claim 1 , wherein the mapping of step b) comprises finding the closest road segment to said positioning data.
5 . A method according to claim 1 , wherein the weight assigned to each mapped point in substep c) ii. is proportional to its distance from the center of the intersection.