Apparatus and method for tracing a geographical journey taken by an entity, for example an article (shipment), asset or person, on a worldwide map uses a miniature, passive, low power, radio receiver tag that is attached to the entity and collects multiple FM spectra during the travels of the entity. When the tag is retrieved at the end of the journey, the FM spectra are downloaded and compared against a collection of constructed spectra constructed from antenna transmission and location data derived. Correlating each of the spectra collected by the receiver tag with the corresponding spectra in the database allows the regions traversed by the receiver tag, and hence the entity, during its travels to be plotted.