Automatic egress/ingress detection in an acoustic positioning system

1. A method of door location in an indoor environment comprising:

locating, by an acoustic location system, a location tag at a first location in a first region within the indoor environment;

locating at a later time, by the acoustic location system, the location tag at a second location in a second region within the indoor environment, wherein the first region is separated from the second region by a partition;

determining a velocity vector of the location tag while the location tag is transitioning from the first region to the second region; and

determining a presence of a door located in the partition, the determining based on a magnitude of an inner product of the velocity vector with a normal vector of the partition exceeding a predetermined threshold.

2. The method of claim 1 , further comprising:

determining an abrupt change of a property of an acoustic signal in locating the location tag at the first location and at the second location; and

confirming the presence of the door based on the determining of the abrupt change.

3. The method of claim 2 , wherein the property is one of time-of-flight-based range or a root sum square (RSS) level.

4. The method of claim 1 , wherein the acoustic location system includes a first acoustic beacon transceiver located in the first region and a second acoustic beacon transceiver located in the second region.

5. The method of claim 1 , wherein the predetermined threshold is 0.15 meters/second.

6. A method of door location in an indoor environment comprising:

locating, by an acoustic location system, a location tag at a first location in a first region within the indoor environment;

receiving data showing a partition associated with the first region;

determining a velocity vector of the location tag in a vicinity of the partition; and

determining a presence of a door located in the partition based on a magnitude of an inner product of the velocity vector with a normal vector of the partition exceeding a predetermined threshold.

7. The method of claim 6 , wherein the predetermined threshold is 0.15 meters/second.

8. The method of claim 6 , wherein the determining the presence of the door further includes determining a location error of the location tag exceeds another predetermined threshold.

9. A computer-implemented method of door location in an indoor environment, the computer-implemented method comprising:

locating, by an acoustic location system, a location tag at a first location in a first region within the indoor environment;

locating at a later time, by the acoustic location system, the location tag at a second location in a second region within the indoor environment, wherein the first region is separated from the second region by a partition;

determining a velocity vector of the location tag while the location tag is transitioning from the first region to the second region; and

determining a presence of a door located in the partition, the determining based on a magnitude of an inner product of the velocity vector with a normal vector of the partition exceeding a predetermined threshold.

10. The computer-implemented method of claim 9 , further comprising:

determining an abrupt change of a property of an acoustic signal in locating the location tag at the first location and at the second location; and

confirming the presence of the door based on the determining of the abrupt change.

11. The computer-implemented method of claim 10 , wherein the property is one of time-of-flight-based range or a root sum square (RSS) level.

12. The computer-implemented method of claim 9 , wherein the acoustic location system includes a first acoustic beacon transceiver located in the first region and a second acoustic beacon transceiver located in the second region.

13. The computer-implemented method of claim 9 , wherein the predetermined threshold is 0.15 meters/second.

14. A computer-implemented method of door location in an indoor environment, the computer-implemented method comprising:

locating, by an acoustic location system, a location tag at a first location in a first region within the indoor environment;

receiving data showing with a partition associated with the first region;

determining a velocity vector of the location tag in a vicinity of the partition; and

determining a presence of a door located in the partition based on a magnitude of an inner product of the velocity vector with a normal vector of the partition exceeding a predetermined threshold.

15. The computer-implemented method of claim 14 , wherein the predetermined threshold is 0.15 meters/second.

16. The computer-implemented method of claim 14 , wherein the determining the presence of the door further includes determining a location error of the location tag exceeds another predetermined threshold.

17. The method of claim 6 , wherein the acoustic location system includes a first acoustic beacon transceiver located in the first region and a second acoustic beacon transceiver located in the second region.

18. The method of claim 6 , further comprising:

repeating the determining the velocity vector and the determining the presence of the door located in the partition over a number of transition events from the first region to the second region; and

analyzing statistical data from the repeating to yield a location of the door.

19. The computer-implemented method of claim 14 , wherein the acoustic location system includes a first acoustic beacon transceiver located in the first region and a second acoustic beacon transceiver located in the second region.

20. The computer-implemented method of claim 14 , further comprising:

repeating the determining the velocity vector and the determining the presence of the door located in the partition over a number of transition events from the first region to the second region; and

analyzing statistical data from the repeating to yield a location of the door.