1. A method of locating difficult access points on a topological map established on the basis of a map of curvilinear distances, comprising the steps of: the map of curvilinear distances is by means of a chamfer mask cataloging the approximate values C(V) of the Euclidean distances by separating a point C 00 of the map from its nearest neighbors V, so as to extract therefrom, at each point C 00 of the map of curvilinear distances, the discrepancies 1(V)−DT( 0 ) 1 of curvilinear distances separating the point considered C 00 from its nearest neighbors V, and comparing these discrepancies 1(V)−DT( 0 ) 1 with the approximate values C(V) of the Euclidean distances of the chamfer mask and describe the point considered as difficult of access when a difference appears.