A method for assisting the movement of an agent between a first point and a second point in an interior of a predetermined zone, the predetermined zone being a building, the first point and the second point being identified by coordinates relating to the predetermined zone, the assistance method comprising a step of calculating a route between the first point and the second point, the route being calculated based on a graph stored in storage means of a graph server, the route being displayed on an assistance device comprising geolocation means producing coordinates relating to the predetermined zone, the method being characterized in that it comprises the following features: - a step prior to the calculation of a route comprising the following steps: - modeling the predetermined zone as elementary volumes and storing these elementary volumes in a zone database; - a step carried out continuously by the assistance device comprising the following steps: - determining the position of the assistance device; - producing and transmitting a position message, comprising at least the determined position, to the graph server; - a step carried out continuously by the graph server comprising the following steps: - receiving a position message; - updating the graph according to the position message, the update being the association of the position message with an elementary volume in the zone database; - a step of calculating a route such that: - a graph to be used for the route calculation is extracted from the model and is such that a vertex of the graph corresponds to each elementary volume, two vertices being connected by an arc if their corresponding elementary volumes are adjacent and if their elementary volumes are associated with at least one position message; - to calculate the route, the first point is associated with a first elementary volume, the second point is associated with a second elementary volume, the route being calculated between the vertices associated with the first elementary volume and with the second elementary volume. - a step prior to the calculation of a route comprising the following steps: - modeling the predetermined zone as elementary volumes and storing these elementary volumes in a zone database; - modeling the predetermined zone as elementary volumes and storing these elementary volumes in a zone database; - a step carried out continuously by the assistance device comprising the following steps: - determining the position of the assistance device; - producing and transmitting a position message, comprising at least the determined position, to the graph server; - determining the position of the assistance device; - producing and transmitting a position message, comprising at least the determined position, to the graph server; - a step carried out continuously by the graph server comprising the following steps: - receiving a position message; - updating the graph according to the position message, the update being the association of the position message with an elementary volume in the zone database; - receiving a position message; - updating the graph according to the position message, the update being the association of the position message with an elementary volume in the zone database; - a step of calculating a route such that: - a graph to be used for the route calculation is extracted from the model and is such that a vertex of the graph corresponds to each elementary volume, two vertices being connected by an arc if their corresponding elementary volumes are adjacent and if their elementary volumes are associated with at least one position message; - to calculate the route, the first point is associated with a first elementary volume, the second point is associated with a second elementary volume, the route being calculated between the vertices associated with the first elementary volume and with the second elementary volume. - a graph to be used for the route calculation is extracted from the model and is such that a vertex of the graph corresponds to each elementary volume, two vertices being connected by an arc if their corresponding elementary volumes are adjacent and if their elementary volumes are associated with at least one position message; - to calculate the route, the first point is associated with a first elementary volume, the second point is associated with a second elementary volume, the route being calculated between the vertices associated with the first elementary volume and with the second elementary volume.