Method and system for locating a position of a movable device

1. A method for locating a movable device within an environment, wherein the movable device is configured for wireless communication, said method comprising:

receiving by the movable device a centrally determined environment model from an external unit, the received centrally determined environment model defining at least locations of wireless transmission sources and defining estimated accuracies of the locations of the wireless transmission sources, the estimated accuracies comprising deviations of at least one spatial dimension of the locations of the wireless transmission sources;

determining distance-dependent measurements for one or more locations of the movable device, wherein each of the determined distance-dependent measurements provides measured wireless signal information relating to a distance between the movable device and a wireless transmission source; and

determining a location of the movable device based on the received centrally determined environment model and the determined distance-dependent measurements for one or more locations of the movable device, said determining comprising:

forming in the movable device a locally determined environment model, the locally determined environment model being updated in relation to the received centrally determined environment model and defining at least the locations of the wireless transmission sources and the one or more locations of the movable device, wherein a calculated error comprising differences between (a) expected distance-dependent measurements and (b) the determined distance-dependent measurements, is reduced in updating the locally determined environment model, and wherein estimated accuracies are taken into account in the calculated error.

2. The method according to claim 1 , wherein the received centrally determined environment model further comprises estimated accuracies of the actual and/or estimated locations of the wireless transmission sources.

3. The method according to claim 1 , wherein the received centrally determined environment model is a subset of one or more models in the external unit.

4. The method according to claim 1 , wherein the calculated error of the locally determined environment model is based on a calculated weighted contribution of errors, wherein each error is based on a difference between a feature defined by the locally determined environment model and a corresponding measurement.

5. The method according to claim 1 , wherein the received centrally determined environment model defines, for each wireless transmission source, a wireless transmission propagation model in the environment for wireless transmission from the source.

6. The method according to claim 1 , wherein the received centrally determined environment model defines propagation properties of a building representing non-uniform structures in the building.

7. The method according to claim 1 , wherein the determined distance-dependent measurements are sequentially determined for a plurality of locations of the movable device while the movable device is moved in the environment, wherein the forming of the locally determined environment model is based on the determined distance-dependent measurements for a defined number of most recent locations among the plurality of locations.

8. The method according to claim 1 , further comprising determining additional measurements relating to the one or more locations of the movable device, wherein the forming of the locally determined environment model defining at least estimated locations of the wireless transmission sources and estimated locations of the one or more locations of the movable device takes into account also an additional error of the locally determined environment model in relation to the determined additional measurements.

9. The method according to claim 8 , wherein the determined additional measurements include at least one of: a position based on a satellite positioning system, sensor data indicating a relative floor in a building, compass data, accelerometer data, gyroscope data, step counter data, data correlating measurements at regular intervals, and manually input measurements.

10. The method according to claim 1 , further comprising transmitting information of the determined distance-dependent measurements and/or information of estimated locations of wireless transmission sources and/or the locally determined environment model to the external unit.

11. The method according to claim 1 , further comprising intermittently receiving an updated centrally determined environment model from the external unit.

12. The method according to claim 1 , wherein the received centrally determined environment model represents a building and differentiates between wireless transmission sources on different floors of the building.

13. The method according to claim 1 , wherein the received centrally determined environment model comprises identifiers of wireless transmission sources, wherein the identifiers are provided in a reduced format.

14. The method according to claim 1 , wherein the received centrally determined environment model defines actual and/or estimated locations of wireless transmission sources in relation to a common reference point in the environment.

15. A computer program product comprising a non-transitory computer-readable medium storing computer-readable instructions which, when executed on a processing unit, causes the processing unit to perform a method for locating a movable device within an environment, wherein the movable device is configured for wireless communication, said method comprising:

receiving by the movable device a centrally determined environment model from an external unit, the received centrally determined environment model defining at least locations of wireless transmission sources and defining estimated accuracies of the locations of the wireless transmission sources, the estimated accuracies comprising deviations of at least one spatial dimension of the locations of the wireless transmission sources;

determining distance-dependent measurements for one or more locations of the movable device, wherein each of the determined distance-dependent measurements provides measured wireless signal information relating to a distance between the movable device and a wireless transmission source; and

determining a location of the movable device based on the received centrally determined environment model and the determined distance-dependent measurements for one or more locations of the movable device, said determining comprising:

forming in the movable device a locally determined environment model, the locally determined environment model being updated in relation to the received centrally determined environment model and defining at least the locations of the wireless transmission sources and the one or more locations of the movable device, wherein a calculated error comprising differences between (a) expected distance-dependent measurements and (b) the determined distance-dependent measurements, is reduced in updating the locally determined environment model, and wherein estimated accuracies are taken into account in the calculated error.