Supporting magnetic flux density based positioning

An apparatus comprising at least one processor and at least one memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform:

• obtain data comprising magnetic flux density data and an association of the magnetic flux density data to grid points of at least one grid, each grid point representing at least a geographical location, wherein the magnetic flux data comprises a representation of magnetic flux density vectors, and wherein at least some representations of a magnetic flux density vector are associated with one of:
• a grid point of a grid representing one of a plurality of geographical areas;
• or
• a grid point of a grid representing the area of a particular building;
• or
• coordinates of a grid point of a two-dimensional grid;
• or
• coordinates of a grid point of one of a plurality of two-dimensional grids, each grid being provided for a different floor number;
• or
• coordinates of a grid point of one of a plurality of two-dimensional grids, each grid being provided for a different altitude;
• or
• coordinates of a grid point of a three-dimensional grid;
• apply at least one frequency transform to a representation of the magnetic flux density data and their association to grid points to obtain frequency components;
• and
• provide compressed magnetic flux density data comprising a subset of the obtained frequency components for at least one of storage and transmission.

A computer readable storage medium in which computer program code is stored, the computer program code causing an apparatus to perform the following when executed by a processor:

• obtain data comprising magnetic flux density data and an association of the magnetic flux density data to grid points of at least one grid, each grid point representing at least a geographical location, wherein the magnetic flux data comprises a representation of magnetic flux density vectors, and wherein at least some representations of a magnetic flux density vector are associated with one of:
• a grid point of a grid representing one of a plurality of geographical areas;
• or
• a grid point of a grid representing the area of a particular building;
• or
• coordinates of a grid point of a two-dimensional grid;
• or
• coordinates of a grid point of one of a plurality of two-dimensional grids, each grid being provided for a different floor number;
• or
• coordinates of a grid point of one of a plurality of two-dimensional grids, each grid being provided for a different altitude;
• or
• coordinates of a grid point of a three-dimensional grid;
• apply at least one frequency transform to a representation of the magnetic flux density data and their association to grid points to obtain frequency components;
• and
• provide compressed magnetic flux density data comprising a subset of the obtained frequency components for at least one of storage and transmission.

A method performed by at least one apparatus, the method comprising:

• obtaining frequency components representing magnetic flux density data and an association of the magnetic flux density data with different grid points of at least one grid in compressed form, each grid point representing at least a geographical location, wherein the magnetic flux data comprises a representation of magnetic flux density vectors, and wherein at least some representations of a magnetic flux density vector are associated with one of:
• a grid point of a grid representing one of a plurality of geographical areas;
• or
• a grid point of a grid representing the area of a particular building;
• or
• coordinates of a grid point of a two-dimensional grid;
• or
• coordinates of a grid point of one of a plurality of two-dimensional grids, each grid being provided for a different floor number;
• or
• coordinates of a grid point of one of a plurality of two-dimensional grids, each grid being provided for a different altitude;
• or
• coordinates of a grid point of a three-dimensional grid;
• applying at least one inverse frequency transform to the frequency components in order to recover the magnetic flux density data and their association with different grid points;
• and
• providing the recovered magnetic flux density data and their association with different grid points for supporting a positioning of a mobile device.

An apparatus comprising at least one processor and at least one memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform:

• obtain frequency components representing magnetic flux density data and an association of the magnetic flux density data with different grid points of at least one grid in compressed form, each grid point representing at least a geographical location, wherein the magnetic flux data comprises a representation of magnetic flux density vectors, and wherein at least some representations of a magnetic flux density vector are associated with one of:
• a grid point of a grid representing one of a plurality of geographical areas;
• or
• a grid point of a grid representing the area of a particular building;
• or
• coordinates of a grid point of a two-dimensional grid;
• or
• coordinates of a grid point of one of a plurality of two-dimensional grids, each grid being provided for a different floor number;
• or
• coordinates of a grid point of one of a plurality of two-dimensional grids, each grid being provided for a different altitude;
• or
• coordinates of a grid point of a three-dimensional grid;
• apply at least one inverse frequency transform to the frequency components in order to recover the magnetic flux density data and their association with different grid points;
• and
• provide the recovered magnetic flux density data and their association with different grid points for supporting a positioning of a mobile device.

A computer readable storage medium in which computer program code is stored, the computer program code causing an apparatus to perform the following when executed by a processor:

• obtain frequency components representing magnetic flux density data and an association of the magnetic flux density data with different grid points of at least one grid in compressed form, each grid point representing at least a geographical location, wherein the magnetic flux data comprises a representation of magnetic flux density vectors, and wherein at least some representations of a magnetic flux density vector are associated with one of:
• a grid point of a grid representing one of a plurality of geographical areas;
• or
• a grid point of a grid representing the area of a particular building;
• or
• coordinates of a grid point of a two-dimensional grid;
• or
• coordinates of a grid point of one of a plurality of two-dimensional grids, each grid being provided for a different floor number;
• or
• coordinates of a grid point of one of a plurality of two-dimensional grids, each grid being provided for a different altitude;
• or
• coordinates of a grid point of a three-dimensional grid;
• apply at least one inverse frequency transform to the frequency components in order to recover the magnetic flux density data and their association with different grid points;
• and
• provide the recovered magnetic flux density data and their association with different grid points for supporting a positioning of a mobile device.