| 摘要 |
An apparatus caused at least to acquire information indicating first indoor magnetic field vectors measured by a first portable device inside a building; generate a first indoor magnetic field sequence, IMFS, on the basis of the first indoor magnetic field vectors; acquire information indicating second indoor magnetic field vectors measured by a second portable device inside the building; generate a second IMFS on the basis of the second indoor magnetic field vectors, wherein the first and the second IMFSs represent at least one of the magnitude and the direction of the Earth's magnetic field; perform a comparison between at least part of the first IMFS and at least part of the second IMFS; and acquire information on the relative movement of the first portable device with respect to the second portable device inside the building on the basis of the comparison result. |
