Abstract: There is provided an apparatus, wherein the apparatus is caused to acquire a location estimate of a positioning device that is to determine its location inside a building, wherein the location estimate is acquired on the basis of an indoor non-magnetic field based location discovery system; access an indoor Earth's magnetic field, EMF, map of plurality of buildings, wherein the indoor EMF map represents at least one of magnitude and direction of the Earth's magnetic field affected by the local structures of a corresponding building; and select a part of the indoor EMF map on the basis of the location estimate of the positioning device, wherein the selected part of the indoor magnetic field map includes the indoor EMF map for the area in which the positioning device currently is.

Abstract: There is provided an apparatus caused to acquire information indicating a measured magnetic field vector and information relating to an uncertainty measure of the measured magnetic field vector in at least one known location inside the building, wherein the indicated magnetic field vector represents magnitude and direction of the earth's magnetic field affected by the local structures of the building, and to generate the indoor magnetic field map for at least part of the building on the basis of at least the acquired information and the floor plan.

Abstract: There is provided a solution comprising detecting that a positioning device is within a predetermined control area associated with a building, 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; determining that an operational environment of the positioning de-vice has changed between an indoor environment and an outdoor environment when a at least one predetermined criterion with respect to the first sequence is met; and causing actuation of a predetermined software function in or with respect to the positioning device when the operational environment of the positioning device has changed.