| 主权项 |
1. An apparatus, comprising:
at least one processor and at least one memory including a computer program code, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to: detect that a positioning device is within a predetermined control area associated with a building; upon detecting that the positioning device is within the predetermined control area, start acquiring a first sequence of magnetic field measurements carried out by the positioning device, wherein the first sequence represents at least one of the magnitude and the direction of Earth's magnetic field; determine that an operational environment of the positioning device has changed between an indoor environment and an outdoor environment when at least one predetermined criterion with respect to at least part of the first sequence is met, wherein the at least one predetermined criterion comprises a predetermined similarity between the first sequence and at least one second magnetic field sequence, wherein each second sequence is determined beforehand and represents a true magnetic field sequence for a path comprising a change of operational environment; compare the first magnetic field sequence and the at least one second true magnetic field sequence in order to obtain at least one path hypothesis for the positioning device, wherein each path hypothesis is associated with a probability that the positioning device has traversed the path corresponding to the second magnetic field sequence; and automatically cause a predetermined operation of an application in or with respect to the positioning device when the operational environment of the positioning device has changed, wherein the operation to be performed is based on the probabilities of the path hypotheses. |
