A portable electronic device is disclosed comprising data processing means and a data repository containing: data records representative of locations relevant to or within a digital map; and data representative of an index associating words contained in the data records with the records in which those words appear. The device further comprises means for, in relation to a received search query including a search string, processing the search string to provide one or more search words; querying the index to identify data records containing the or each search word; and generating a rank for each of the one or more identified data records indicative of the relevance of each identified data record to the search query.