Determining A Dilution of Precision Metric Using Two or Three GPS Satellites
The disclosed subject matter relates to a method for determining a Dilution of Precision Metric (DOP) with less than four satellites in a hybrid positioning system. In some embodiments, the method includes determining an initial position estimate of a device using a non-satellite positioning system, obtaining satellite measurements from less than four satellites, wherein the measurements include each satellite's position with respect to the initial position estimate, constructing a geometry matrix corresponding to the measurements from the less than four satellites using each satellite's position and the initial position estimate, multiplying the geometry matrix by its transpose to construct an H matrix, determining an inverse of the H matrix, and determining the DOP based on a sum of the diagonal elements of the inverse H matrix. In some embodiments, the non-satellite positioning system is a WLAN positioning system.
1 . A method for determining a Dilution of Precision Metric (DOP) with less than four satellites in a hybrid positioning system, the method comprising:
determining an initial position estimate of a device using a non-satellite positioning system;
obtaining satellite measurements from less than four satellites, wherein the measurements include each satellite's position with respect to the initial position estimate;
constructing a geometry matrix corresponding to the measurements from the less than four satellites using each satellite's position and the initial position estimate;
multiplying the geometry matrix by its transpose to construct an H matrix;
determining an inverse of the H matrix; and
determining the DOP based on a sum of the diagonal elements of the inverse H matrix.
2 . The method of claim 1 wherein the non-satellite positioning system is a WLAN positioning system.
3 . The method of claim 1 comprising obtaining satellite measurements from three satellites.
4 . The method of claim 1 comprising selecting a set of satellites based on the value of the DOP.
5 . The method of claim 1 comprising selecting a set of satellites to integrate in hybrid positioning system with the non-satellite positioning system if the DOP is small.
6 . The method of claim 5 , wherein a small DOP corresponds to set of satellites which display good geometry in reference to the location of the mobile device.
7 . The method of claim 5 , wherein a small value of DOP comprises a value between about 1.4 to about 2.5.
8 . The method of 1 comprising not selecting the set of satellites to determine the position the mobile device and reporting the initial position estimate if DOP is large.
9 . The method of claim 8 , wherein a large DOP corresponds to satellites that are display poor geometry in reference to the position of the mobile device.
10 . The method of claim 8 , wherein a large value of DOP comprises 3.0.
11 . A method for determining value of a Dilution of Precision Metric (DOP) with less than four satellites in a hybrid positioning system, the method comprising:
determining an initial position estimate of a device using a non-satellite positioning system;
obtaining satellite measurements from a set of three satellites, wherein the measurements include each satellite's position with respect to the initial position estimate;
rotating the set of satellites to form a rotated set of satellites having standard coordinates;
determining a rotated geometry matrix using angles between the rotated set of satellites and the set of rotated axes;
multiplying the geometry matrix by a transpose of the rotated geometry matrix to create an H matrix; and
determining a DOP based on the diagonal elements of the inverse of the H matrix.
12 . The method of claim 11 wherein the non-satellite positioning system is a WLAN positioning system.
13 . The method of claim 11 comprising selecting a set of satellites based on the value of DOP.
14 . The method of claim 11 comprising selecting a set of satellites to integrate in the hybrid positioning in order to improve the position estimate if the DOP is small.
15 . The method of claim 14 , wherein a small DOP corresponds to set of satellites which display good geometry in reference to the location of the mobile device
16 . The method of 11 comprising refining the initial position estimate if the DOP is small.
17 . The method of claim 16 , wherein a small value of DOP comprises a value between about 1.4 to about 2.5.
18 . The method of 11 comprising reporting the initial position estimate if the DOP is large.
19 . The method of claim 18 , wherein a large DOP corresponds to satellites that display poor geometry in reference to the position of the mobile device.
20 . The method of claim 19 , wherein a large value of DOP comprises 3.0.
21 . A method for determining a Dilution of Precision Metric (DOP) with less than four satellites in a hybrid positioning system, the method comprising:
determining an initial position estimate of a device using a non-satellite positioning system;
obtaining satellite measurements from less than four satellites, wherein the measurements include each satellite's position with respect to the initial position estimate; and
determining a DOP based on the initial position estimate and the satellite measurements from less than four satellites.
22 . The method of claim 21 wherein the non-satellite positioning system is a WLAN positioning system.
23 . The method of claim 21 comprising obtaining satellite measurements from two satellites.
24 . The method of claim 23 , wherein the DOP is related to the angle between the two satellites with respect to the initial position estimate.
25 . The method of claim 21 comprising obtaining satellite measurements from three satellites.
26 . The method of claim 21 comprising selecting a set of satellites based on the value of DOP.
27 . The method of claim 21 comprising selecting a set of satellites to integrate in the hybrid positioning in order to improve the position estimate if the DOP is small.
28 . The method of claim 27 , wherein a small DOP corresponds to set of satellites which display good geometry in reference to the location of the mobile device
29 . The method of 27 comprising refining the initial position estimate if the DOP is small.
30 . The method of claim 27 , wherein a small value of DOP comprises a value between about 1.4 to about 2.5.
31 . The method of 21 comprising reporting the initial position estimate if the DOP is large.
32 . The method of claim 31 , wherein a large DOP corresponds to satellites that display poor geometry in reference to the position of the mobile device.
33 . The method of claim 31 , wherein a large value of DOP comprises 3.0.