Location estimation by observing wireless signals

A non-transitory computer readable medium, the computer readable medium including code instructing a processor to perform steps of:

• receiving an observation including the identity of at least one wireless transmitter detected by a device at the position to be estimated;
• comparing the observation with a plurality of records, each record comprising the identity of one or more wireless transmitters and a corresponding position, the position being based on a location or set of locations at which the one or more transmitters were detected, each record originating from a source other than the wireless transmitter which may be determined from the record;
• detecting a first match between the observation and a first record, the first record comprising a corresponding first position;
• determining a first indication of the source of the first record;
• detecting a second match between the observation and a second record, the second record comprising a corresponding second position;
• determining a second indication of the source of the second record, wherein the second indication is different from the first indication;
• and
• estimating the position of the electronic device based on at least one of the first and second positions, depending upon the first indication and the second indication
• wherein the first and second indications suggest that the first record originates from a source that is more closely related to the electronic device that the source of the second record, wherein:
• if the second match is more specific than the first match, then the estimation of the position of the electronic device is based preferentially on the second position;
• otherwise the estimation is based preferentially on the first position.

A portable device, comprising:

• a wireless receiver, adapted to observe the identity of at least one wireless transmitter detectable by the device at a position to be estimated;
• a query processor, operable to issue the observed identity as a query to be compared with a plurality of records in a database, each record comprising the identity of one or more wireless transmitters and a corresponding position, the position being based on a location or set of locations at which the one or more transmitters were detected, each record in the database originating from a source other than the wireless transmitter which may be determined from the record in the database,
• the query processor being operable to receive, in response to the query, the result of a first match between the observation and a first one of the records, the result comprising:
• a first indication of the source of the first record;
• a first position estimate, being the position corresponding to the first record,
• the query processor also being operable to receive, in response to the query, the result of a second match between the observation and a second one of the records, the result comprising:
• a second indication of the source of the second record, wherein the second indication is different from the first indication;
• a second position estimate, being the position corresponding to the second record;
• and
• a position estimator, adapted to estimate the position of the portable device based on at least one of the first position estimate and the second position estimate, depending upon the first indication and the second indication
• wherein the first and second indications suggest that the first record originates from a source that is more closely related to the portable device than the source of the second record, wherein:
• if the second match is more specific than the first match, then the estimation of the position of the portable device is based preferentially on the second position;
• otherwise the estimation is based on the first position.