Altitude-based indoor or outdoor detection

Abstract

Using estimates of a receiver's altitude to determine where a receiver is located and to refine a positioning system's estimate of a receiver's position. Systems and methods determine whether a receiver is inside or outside a building, and may use the determination to confirm or adjust an initial estimate of the receiver's position. Various approaches for making the determination and for assessing the initial estimate of the receiver's position are described.

1 . A method for improving an estimated position using altitude-based indoor/outdoor detection, the method comprising:
 determining an estimated position of a receiver;   determining an estimated altitude of the receiver;   identifying an altitude associated with the estimated position;   determining if a relationship between the estimated altitude and the identified altitude meets a first condition;   determining if the receiver is inside or outside a building depending on whether the relationship meets the first condition; and   improving one or both of the estimated position or the estimated altitude based on determining whether the receiver is inside or outside.   
     
     
         2 . The method of  claim 1 , wherein identifying an altitude associated with the estimated position comprises:
 identifying a point of reference using the estimated position;   identifying an altitude associated with the point of reference; and   using the altitude of the point of reference as the identified altitude.   
     
     
         3 . The method of  claim 2 , wherein the point of reference has location parameters that are within a threshold distance of the estimated position. 
     
     
         4 . The method of  claim 1 , wherein determining if a relationship between the estimated altitude and the identified altitude meets a first condition comprises:
 determining an altitude difference between the estimated altitude and the identified altitude, wherein the first condition is met if the altitude difference is greater than a threshold value.   
     
     
         5 . The method of  claim 1 , wherein determining if the receiver is inside or outside the building depending on whether the relationship meets the first condition comprises:
 determining, if the relationship meets the first condition, that the receiver is inside the building; and   determining, if the relationship does not meet the first condition, that the receiver is outside the building.   
     
     
         6 . The method of  claim 1 , wherein determining if a relationship between the estimated altitude and the identified altitude meets a first condition comprises:
 determining if the estimated altitude is greater than the identified altitude,   wherein the first condition is met if the estimated altitude is greater than the identified altitude.   
     
     
         7 . The method of  claim 1 , wherein determining if a relationship between the estimated altitude and the identified altitude meets a first condition comprises:
 determining an altitude difference between the estimated altitude and the identified altitude; and   generating, using the altitude difference, a confidence value representing a confidence that the receiver is inside a building and not outside a building,   wherein the first condition is met if the confidence value satisfies a threshold criteria.   
     
     
         8 . The method of  claim 1 , wherein determining if the receiver is inside or outside the building depending on whether the relationship meets the first condition comprises:
 determining, if the relationship meets the first condition, that the receiver is inside the building; and   if the relationship does not meet the first condition:
 identifying one or more generated confidence values; 
 receiving input regarding a first consideration; 
 generating another confidence value using the input, 
 wherein the other confidence value represents a confidence that the receiver is inside the building and not outside the building; 
 generating a combined confidence value using the one or more generated confidence values and the other confidence value; and 
 determining if the receiver is inside or outside the building using the combined confidence value. 
   
     
     
         9 . The method of  claim 8 , wherein one of the one or more generated confidence values is generated using an altitude difference. 
     
     
         10 . The method of  claim 8 , wherein the input regarding the first consideration is a measure of an ambient audio level. 
     
     
         11 . The method of  claim 8 , wherein the combined confidence value is generated by averaging the one or more generated confidence values and the other confidence value. 
     
     
         12 . The method of  claim 1 , wherein determining if the receiver is inside or outside the building depending on whether the relationship meets the first condition comprises:
 determining, if the relationship meets the first condition, that the receiver is inside the building; and   determining, if the relationship does not meet the first condition, whether the receiver is outside or inside the building based on one or more other considerations,   wherein the one or more other considerations includes whether one or more of a measure of ambient audio, a measure of ambient temperature, a measure of RF noise, or a measure of signal strength match a corresponding threshold value of audio, temperature, RF noise, or signal strength identified for an indoor environment or an outdoor environment.   
     
     
         13 . The method of  claim 1 , wherein improving one or both of the estimated position or the estimated altitude based on determining whether the receiver is inside or outside comprises:
 using the estimated altitude, or the estimated position to identify a bounding polygon associated with a floor in a building; and   projecting the estimated position of the receiver onto the bounding polygon to generate another estimate of the receiver's position.   
     
     
         14 . The method of  claim 13 , wherein the other estimate of the receiver's position is used as an input to a position estimation algorithm. 
     
     
         15 . The method of  claim 14 , wherein the position estimation algorithm comprises a Kalman Filter. 
     
     
         16 . The method of  claim 13 , wherein using the estimated altitude, or the estimated position to identify a bounding polygon associated with a floor in a building comprises:
 identifying a floor in the building that matches the estimated altitude of the receiver; and   identifying a bounding polygon associated with that floor.   
     
     
         17 . A system for improving an estimated position using altitude-based indoor/outdoor detection, wherein the system includes one or more modules that are operable to perform the method of  claim 1 . 
     
     
         18 . One or more non-transitory machine-readable media embodying program instructions that, when executed by one or more machines, cause the one or more machines to perform the method of  claim 1 .