AN EFFICIENT LOCATION REFERENCING METHOD

A efficient method of encoding a continuous path within a road network is described. Ideally the path to be encod-ed is capable of being completely represented within a digital map and expressible as a path list of lines and/or segments existing in said digital map and consecutively ordered. The method comprises the steps of. (i) storing a start position in a route search list, said start position being one of. (a) the line or segment first appearing in said path list or, where the start node of said first line or segment is artificial, the first line or segment appearing in said digital map having a real start node and which leads directly to said first line or segment optionally through other artificial nodes, or (b) a most recently identified deviation line or segment also ap-pearing in said path list; (ii) determining a path from the start node of the start position and including said start position to an end node of the last line or segment in the path list within said digital map, said path being determined according to an algorithm, (iii) comparing the shortest path so determined to the path list for identity, and in the absence of identity, identifying at least one devia-tion line or segment being part of the path list and having a start node representative of an intersection in said digital map but not being the line or segment first appearing in said path list, and if such deviation line or segment does not terminate at the end node of the last line or segment appearing in the path list, repeating step (i) using said deviation line or segment, and (iv) Storing the last line or segment in the path list in said route search list if not already stored. Most preferably, the algorithm used is a shortest path algorithm. Linvention concerne un procédé efficace de codage dun trajet continu dans un réseau routier. Idéalement, le trajet devant être codé peut être complètement représenté dans une carte numérique et peut être exprimé sous forme de liste de trajets constitués de lignes et/ou segments existant dans ladite carte numérique et classés consécutivement. Ce procédé comprend les étapes consistant à : (i) enregistrer une position de départ dans une liste de recherche ditinéraire, ladite position de départ étant : soit (a) la ligne ou le segment apparaissant en premier dans ladite liste de trajets ou, lorsque le nud de départ dudit premier segment ou de ladite première ligne est artificiel, le premier segment ou la première ligne apparaissant dans ladi