Patent ID: 8174447

Claim:
An apparatus for localizing a current position of a terminal device or for navigating the terminal device on a guidance path, radio signals of fixedly positioned radio transmitters being receivable along the path, the apparatus comprising: a comparator arranged to compare previously recorded electromagnetic properties of the radio signals of the fixedly positioned radio transmitters, which unambiguously identify a measurement point, so as to examine several reference paths to search for an intersection point on the basis of common features of the previously recorded electromagnetic properties, wherein the intersection point characterizes an identical geographic position in different reference paths, and to interconnect the reference paths to form a graph, the intersection point and the current position of the terminal device being regarded as nodes, and portions of paths between the intersection point and the current position of the terminal device being regarded as edges of the graph, and a reference path being distinguished by a temporal succession of the previously recorded electromagnetic properties; a guidance path determiner arranged to determine the guidance path from the current position to the intersection point, the guidance path determiner being configured to determine the guidance path by use of a routing algorithm on the basis of the graph, the guidance path having associated previously recorded electromagnetic properties; and a properties determiner arranged to determine current properties of the radio signals of the fixedly positioned radio transmitters at the current position of the terminal device, the current properties of the radio signals comprising electromagnetic properties of the radio signals of the fixedly positioned radio transmitters; wherein the comparator is configured to compare the current electromagnetic properties of the radio signals with the previously recorded electromagnetic properties of the radio signals associated with the guidance path, and to determine a relation between the current position of the terminal device and the guidance path on the basis of a result of the comparison.