Method of determining routes between a point of departure (a) and a point of arrival (β) for a route calculation device, comprising: - a data input unit, for receiving the data associated with a point of departure and those associated with a point of arrival; - access to a storage unit comprising a set of road network modelling elements forming a digital road mapping system consisting of a set of segments and nodes each having their importance index, said nodes and segments being put together so as to represent a road network formed of a plurality of meshes of different importance indices, each of the meshes being defined by a set of nodes and segments of a given index; - a calculation unit designed for identifying a plurality of routes enabling each to connect the points of departure and arrival; - means of elimination, first for identifying at least one elimination level or threshold and secondly for eliminating at least one portion of the basic set of data whose index is below said elimination level or threshold; said method comprising the following steps: - in order to determine the route, a plurality of potential routes is identified from which one route is selected according to given criteria; - the plurality of routes is identified by selecting a first modelling element of the road network, preferably a node, close to the point of departure, and a second modelling element of the road network, preferably a node, close to the point of arrival, identifying a plurality of routes, each consisting of a plurality of route elements connected from the first element to the second element, and searching for at least one intermediate element for each of said routes in said set of road network modelling elements; - using the calculation unit, the nodes surrounding said departure node and said arrival node are scanned via the segments, so as to determine the cost of each of these nodes; - said scanning is continued until a selected route is reached; said method being characterized by the following steps: a) during said scanning, the nodes are scanned so as to identify the nodes that can be used to form a mesh with a given starting index Id; b) when a mesh with an index Id is identified, using said means of elimination, the segments whose index is less than this index Id are eliminated; c) scanning the nodes continues so as to identify the nodes that can be used to form a new mesh, whose index Is is greater than that of the preceding mesh; d) segments whose index is less than this new index Is are eliminated; e) steps c and d are repeated until a maximum index Im of elimination is reached, so that a network level is eliminated as soon as all the nodes forming the network scanning boundary have an index greater than the given network level. - a data input unit, for receiving the data associated with a point of departure and those associated with a point of arrival; - access to a storage unit comprising a set of road network modelling elements forming a digital road mapping system consisting of a set of segments and nodes each having their importance index, said nodes and segments being put together so as to represent a road network formed of a plurality of meshes of different importance indices, each of the meshes being defined by a set of nodes and segments of a given index; - a calculation unit designed for identifying a plurality of routes enabling each to connect the points of departure and arrival; - means of elimination, first for identifying at least one elimination level or threshold and secondly for eliminating at least one portion of the basic set of data whose index is below said elimination level or threshold; - in order to determine the route, a plurality of potential routes is identified from which one route is selected according to given criteria; - the plurality of routes is identified by selecting a first modelling element of the road network, preferably a node, close to the point of departure, and a second modelling element of the road network, preferably a node, close to the point of arrival, identifying a plurality of routes, each consisting of a plurality of route elements connected from the first element to the second element, and searching for at least one intermediate element for each of said routes in said set of road network modelling elements; - using the calculation unit, the nodes surrounding said departure node and said arrival node are scanned via the segments, so as to determine the cost of each of these nodes; - said scanning is continued until a selected route is reached; a) during said scanning, the nodes are scanned so as to identify the nodes that can be used to form a mesh with a given starting index Id; b) when a mesh with an index Id is identified, using said means of elimination, the segments whose index is less than this index Id are eliminated; c) scanning the nodes continues so as to identify the nodes that can be used to form a new mesh, whose index Is is greater than that of the preceding mesh; d) segments whose index is less than this new index Is are eliminated; e) steps c and d are repeated until a maximum index Im of elimination is reached, so that a network level is eliminated as soon as all the nodes forming the network scanning boundary have an index greater than the given network level.