Efficient location referencing method

A method of encoding a continuous path within a road network, said path 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, wherein said lines and/or segments have one or more attributes associated therewith, said method comprising the steps of:

• (i) storing a start position in a route search list, said start position being one of:
• 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,
• a most recently identified deviation line or segment also appearing 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 utilising an attribute of said lines or segments,
• (iii) comparing the shortest path so determined to the path list for identity, and in the absence of identity, identifying at least one deviation 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.

An encoder comprising at least one processor arranged to encode a continuous path within a road network, said path 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, wherein said lines and/or segments have one or more attributes associated therewith, said encoding comprising the steps of:

• storing a start position in a route search list;
• determining a path from the start position to an end position as indicated by the last line or segment in the path list within said digital map, said path being determined according to an algorithm utilizing an attribute of said lines or segments;
• and
• encoding the continuous path using the determined path.