Patent ID: 8032299

Claim:
A method for determining a road or a set of passable roads or areas traveled by a user with a minimum associated probability or integrity which comprises: receiving from a positioning system information relating to first and second position solutions of said user in a first instant of time t a and in a second instant t b after the first instant t a , respectively, as well as respective position integrity ellipses, I a and I b , with respective minimum associated probabilities, P a and P b , that the user is located in each of them in t a and in t b , respectively, and a position increase Δ ab between t a and t b with its position increase integrity ellipse I ab and its associated probability P ab ; obtaining from a geographic information system, information regarding respective passable areas corresponding to said first and second position solutions; determining a first passable integral area S a and a second passable integral area S b as an intersection for each instant of time of said position integrity ellipses with said passable areas; propagating said first passable integral area to the subsequent instant t b by means of the position increase Δ ab between the first and second instants of time provided by the positioning system, taking into account the uncertainty associated to said increase determined by the position increase integrity ellipse I ab , a propagated integral area S ab being obtained; eliminating from said propagated integral area S ab the non-passable areas, a propagated passable integral area S′ ab being obtained; determining a final passable integral area S′ b formed by a road or a set of passable roads in the second instant t b , either as the smallest of said second passable integral area S b and said propagated passable integral area S′ ab or as the intersection of said second passable integral area S b and of said propagated passable integral area S′ ab ; and determining the minimum probability P′ b that the user is located in said final passable integral area S′ b in the second instant t b or integrity level of S′ b according to one of the following: in the event that said final passable integral area S′ b is said second passable integral area S b , as the probability P b associated to the integrity ellipse I b of said second position solution, i.e. P′ b =P b ; in the event that said final passable integral area S′ b is said propagated passable integral area S′ ab , as the product of the probability P a associated to the first passable area S a , given by the integrity ellipse I a of said first position solution, and the probability associated to the integrity ellipse I ab corresponding to the relative increase of position Δ ab between t a and t b , i.e. P′ b =P a ·P ab ; in the event that said final passable integral area S′ b is determined as the intersection of the second passable integral area S b and said propagated passable integral area S′ ab , by means of the expression: P′ b ≧P a ·P ab +P b −1.