Abstract: There is provided 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, with the at least one processor, to cause the apparatus at least to: perform a set of Earth's magnetic field, EMF, measurements inside a building, wherein each EMF measurement result represents at least one of a magnitude and a direction of the EMF in the building; store the set of EMF measurement results off-line into a memory buffer coupled to the apparatus; and upon detecting a predefined triggering condition, cause a transfer of the stored set of EMF measurement results to a database entity.

Abstract: There is provided a database entity for generating a search database, 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, with the at least one processor, to cause the database entity at least to: acquire, from each of the plurality of mobile devices, an indication of at least one object; acquire a reference sensor, fingerprint representing a context to which the at least one object is related to; associate each object with the corresponding reference sensor fingerprint; and generate a database of associations between the reference sensor fingerprints and the objects.

Abstract: There is provided a database entity for generating a search database, 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, with the at least one processor, to cause the database entity at least to: acquire, from each of the plurality of mobile devices, an indication of at least one object; acquire a reference Earth's magnetic field, EMF, fingerprint representing at least one of magnitude and direction of the EMF in a location and/or environment to which the at least one object is related to; associate each object with the corresponding reference EMF fingerprint; and generate a database of associations between the reference EMF fingerprints and the objects.

Abstract: Provided is an apparatus caused at least to: acquire a set of Earth's magnetic field, EMF, measurement results, wherein each EMF measurement result represents at least one of a magnitude and a direction of the EMF as experienced by a mobile device; perform, on the basis of the set of EMF measurement results, a first observation indicating that the mobile device is currently in motion; acquire a set of inertial measurement results, wherein each inertial measurement result represents at least one of acceleration and angular velocity experienced by the mobile device; perform, on the basis of the set of inertial measurement results, a second observation indicating that the motion of the mobile device does not exceed a predefined stationarity threshold; and determine, on the basis of the first and second observations, that the mobile device is currently located in a transport unit which is moving with respect to surrounding environment.

Abstract: There is provided an apparatus configured to: acquire Earth's magnetic field, EMF, measurement results indicating the EMF measured by a mobile device in a building, wherein the EMF measurements are performed by the mobile device in an unknown three-dimensional orientation in a three-dimensional coordinate system of a person carrying the mobile device along a movement direction of the person; acquire motion data of the mobile device, wherein the motion data is measured by at least one inertial measurement unit comprised in the mobile device; determine at least one angle estimate of a difference between the three-dimensional orientation of the mobile device and at least one dominant movement direction on the basis of at least one feature related to the at least one dominant movement direction of the mobile device; and adjust the acquired EMF measurement results on the basis of the determined at least one angle estimate.

Abstract: There is provided 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, with the at least one processor, to cause the apparatus at least to: perform a set of Earth's magnetic field, EMF, measurements inside a building, wherein each EMF measurement result represents at least one of a magnitude and a direction of the EMF in the building; store the set of EMF measurement results off-line into a memory buffer coupled to the apparatus; and upon detecting a predefined triggering condition, cause a transfer of the stored set of EMF measurement results to a database entity.