WO2011041430A1 - Détermination de position dans un système de positionnement hybride en utilisant une mesure d'atténuation de précision - Google Patents

Détermination de position dans un système de positionnement hybride en utilisant une mesure d'atténuation de précision Download PDF

Info

Publication number
WO2011041430A1
WO2011041430A1 PCT/US2010/050742 US2010050742W WO2011041430A1 WO 2011041430 A1 WO2011041430 A1 WO 2011041430A1 US 2010050742 W US2010050742 W US 2010050742W WO 2011041430 A1 WO2011041430 A1 WO 2011041430A1
Authority
WO
WIPO (PCT)
Prior art keywords
satellites
dop
satellite
positioning system
initial position
Prior art date
Application number
PCT/US2010/050742
Other languages
English (en)
Inventor
Farshid Alizadeh-Shabdiz
Mohammad A. Heidari
Original Assignee
Skyhook Wireless, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US12/572,524 external-priority patent/US8279114B2/en
Priority claimed from US12/572,516 external-priority patent/US20110080318A1/en
Application filed by Skyhook Wireless, Inc. filed Critical Skyhook Wireless, Inc.
Publication of WO2011041430A1 publication Critical patent/WO2011041430A1/fr

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/13—Receivers
    • G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system
    • G01S19/28—Satellite selection
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/38—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system
    • G01S19/39—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/42—Determining position
    • G01S19/45—Determining position by combining measurements of signals from the satellite radio beacon positioning system with a supplementary measurement
    • G01S19/46—Determining position by combining measurements of signals from the satellite radio beacon positioning system with a supplementary measurement the supplementary measurement being of a radio-wave signal type

Definitions

  • the present disclosure generally relates to hybrid positioning systems and more specifically, the assessment of the quality of a set of visible satellites to be used in a positioning system.
  • GPS Global Positioning System
  • a user equipped with a GPS receiver can estimate his three-dimensional position (latitude, longitude, and altitude) anywhere at any time within several meters of the true location as long as the receiver can see enough of the sky to have four or more satellites "in view.”
  • Cellular carriers can use signals originating from and received at cell towers to determine a user's or a mobile device's location.
  • Assisted GPS AGPS is another model that combines both GPS and cellular tower techniques to estimate the locations of mobile users who may be indoors and must cope with attenuation of GPS signals on account of sky blockage.
  • the cellular network attempts to help a GPS receiver improve its signal reception by transmitting information about the satellite positions, their clock offsets, a precise estimate of the current time, and a rough location of the user based on the location of cell towers. No distinction is made in what follows between GPS and AGPS.
  • Satellite-based Positioning System SPS
  • GLONASS Globalstar Satellite-based Positioning System
  • Galileo European system
  • All such systems are referred to herein as SPS.
  • GPS, GLONASS and Galileo are all based on the same basic idea of trilateration, i.e., estimating a position on the basis of measurements of ranges to the satellites whose positions are known. In each case, the satellites transmit the values of certain parameters which allow the receiver to compute the satellite position at a specific instant.
  • the ranges to satellites from a receiver are measured in terms of the transit times of the signals. These range measurements can contain a common bias due to the lack of synchronization between the satellite and receiver (user device) clocks, and are referred to as pseudoranges.
  • the lack of synchronization between the satellite clock and the receiver (user device) clock can result in a difference between the receiver clock and the satellite clock, which is referred to as internal SPS receiver clock bias or receiver clock bias, here.
  • internal SPS receiver clock bias or receiver clock bias In order to estimate a three dimensional position there is a need for four satellites to estimate receiver clock bias along with three dimensional measurements. Additional measurements from each satellite correspond to pseudorange rates in the form of Doppler frequency.
  • References below to raw SPS measurements are intended generally to mean pseudoranges and Doppler frequency measurements.
  • References to SPS data are intended generally to mean data broadcast by the satellites.
  • References to an SPS equation are intended to mean a mathematical equation relating the measurements and data from a satellite to the position and velocity
  • WLAN-based positioning is a technology which uses WLAN access points to determine the location of mobile users.
  • PlaceLab www.placelab.com, a project sponsored by Microsoft and Intel
  • the University of California San Diego ActiveCampus project (ActiveCampus - Sustaining Educational Communities through Mobile Technology, technical report #CS2002- 0714); and the MIT campus-wide location system.
  • WPS WiFi positioning system
  • SPS is based on triangulation (trilateration) using multiple distance measurements from multiple satellites.
  • the receiver measures its distance from at least four satellites. Based on the distance measurements, the receiver solves a set of quadratic equations
  • DOPo Dilution of Precision
  • DOPo metrics and values such as Horizontal Dilution of Precision (HDOP) or Position Dilution of Precision (PDOP)
  • HDOP Horizontal Dilution of Precision
  • PDOP Position Dilution of Precision
  • DOPo metric can be measured differently with different scales, but its importance is to provide a means to assess the quality of the set of visible satellites.
  • satellites For example, if all the satellites are exactly above the location of the receiver or very close to one another that set of satellites cannot be used for positioning. Geometrically, satellites should be spread apart in the sky. The best condition is one satellite above the receiver and others evenly distributed in the sky with good visibility by the receiver. In best scenarios, if all the satellites have angle of 60 degrees to one another, that geometry of satellites can provide more accurate results for positioning. Angles of less than 30 degrees result in satellites which are either close to one another or aligned on the same line that connects them to the receiver. Very wide angles such as 150 degrees also provide satellites which are very far from one another and hence they can only be visible from the horizon with respect to a GPS receiver. Such cases provide bad geometry for satellite positioning.
  • Satellites in the proximity of other satellites and/or satellites aligned on the same plane are normally not useful in location determination as they provide redundant information about receiver. For example, two satellites which are close to one another provide the same range estimation to the receiver and hence one of range estimations can be ignored. Similarly, when satellites are aligned in such a way that the plane which passes through them also passes through the receiver location (or close by locations) the range estimation from the satellites to the receiver are not independent and become redundant. In both cases, the algorithm which solves the range estimation equations to find the receiver location will fail (or converge very slowly) as its input includes redundant data.
  • DOPo only applies to the cases where the receiver can see four or more satellites as described below. With fewer satellites, it is mathematically impossible to obtain a DOPo value when traditional methods are used.
  • the traditional method of obtaining all DOPo metrics is to use the estimated location of receiver, (x r , y r , z r ) , and each of the visible satellites (four or more),
  • each ⁇ component can be determined as follows,
  • R i is the estimated range between the estimated receiver location and i the satellite.
  • matrix G has dimension n x 4 , where n represents the number of visible satellites.
  • the inverse of matrix H denoted by H 1 , is used to determine the DOP values.
  • the diagonal elements of H 1 are used to form Position Dilution of Precision (PDOP) and Time Dilution of Precision (TDOP).
  • PDOP Position Dilution of Precision
  • TDOP Time Dilution of Precision
  • Other DOPo values such as HDOP or Vertical Dilution of Precision (VDOP), are computed similarly.
  • DOPo values can be related to the geometry of the set of satellites.
  • a good set of satellites for SPS is a set of satellites that are well-spread in the sky. Very close satellites or coplanar satellites provide very little
  • Fig. 1 illustrates a good set of satellites versus a bad set of satellites. Relating the geometry of satellites to DOPo values, we can conclude that a good set of satellites results in smaller DOPo values and a bad set of satellites results in large DOPo values. Therefore, it is very instructive and significant to obtain DOPo values for a specific set of satellites relative to an estimated receiver location.
  • the positioning system in our case an integrated WLAN-PS and SPS environment, can effectively decide if a set of satellites is usable for positioning or if it has a bad geometry and will produce large location error.
  • the DOPo value is directly related to the volume of the tetrahedron formed using each satellite as an end point of the tetrahedron (in case of four satellites) or similar shapes (in case of more than four satellites) formed by the satellites.
  • the smallest number of satellites to form an invertible H matrix is four.
  • SPS SPS
  • fewer than four satellites results in H AxA with dependent rows and consequently H ⁇ l does not exist.
  • This fact poses a problem for hybrid positioning schemes with fewer than four visible satellites.
  • the goal is for a positioning scheme to assess the quality of a set of visible satellites. What is needed is a metric to relate the geometry of the visible satellites to quality of the set of visible satellites and to improve the quality of the estimate of the receiver's location when fewer than four satellites are present.
  • the present application relates to a method for determining a Dilution of Precision Metric (DOP) with less than four satellites in a hybrid positioning system.
  • DOP Dilution of Precision Metric
  • 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.
  • the non-satellite positioning system is a WLAN positioning system.
  • the method includes obtaining satellite measurements from three satellites.
  • the method includes selecting a set of satellites based on the value of the DOP. In some embodiments, the method includes selecting a set of satellites to integrate in hybrid positioning system with the non-satellite positioning system if the DOP is small. In some embodiments, a small DOP corresponds to set of satellites which display good geometry in reference to the location of the mobile device. In some embodiments, a small value of DOP comprises a value between about 1.4 to about 2.5. In some embodiments, the method includes not selecting the set of satellites to determine the position the mobile device and reporting the initial position estimate if DOP is large. In some embodiments, a large DOP corresponds to satellites that are display poor geometry in reference to the position of the mobile device. In some embodiments, a large value of DOP comprises 3.0.
  • One aspect of the present disclosure relates to a method including 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.
  • the non-satellite positioning system is a WLAN positioning system.
  • the method includes selecting a set of satellites based on the value of DOP.
  • the method includes selecting a set of satellites to integrate in the hybrid positioning in order to improve the position estimate if the DOP is small.
  • a small DOP corresponds to set of satellites which display good geometry in reference to the location of the mobile device.
  • the method includes refining the initial position estimate if the DOP is small.
  • a small value of DOP comprises a value between about 1.4 to about 2.5.
  • the method includes reporting the initial position estimate if the DOP is large.
  • a large DOP corresponds to satellites that display poor geometry in reference to the position of the mobile device.
  • a large value of DOP comprises 3.0.
  • 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, the method including 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.
  • the non-satellite positioning system is a WLAN positioning system.
  • the method includes obtaining satellite
  • the DOP is related to the angle between the two satellites with respect to the initial position estimate.
  • the method includes obtaining satellite measurements from three satellites.
  • the method includes selecting a set of satellites based on the value of DOP. In some embodiments, the method includes selecting a set of satellites to integrate in the hybrid positioning in order to improve the position estimate if the DOP is small. In some
  • a small DOP corresponds to set of satellites which display good geometry in reference to the location of the mobile device.
  • the method includes refining the initial position estimate if the DOP is small.
  • a small value of DOP comprises a value between about 1.4 to about 2.5.
  • the method includes reporting the initial position estimate if the DOP is large.
  • a large DOP corresponds to satellites that display poor geometry in reference to the position of the mobile device.
  • a large value of DOP comprises 3.0.
  • the present application also relates to a method for determining the position of a device in a hybrid positioning system.
  • 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, determining a dilution of precision (DOP) based on the satellite measurements, if the DOP is small, refining the initial position estimate using the satellite measurements, and if the DOP is large, providing the initial estimate as a final position estimate for the device.
  • DOP dilution of precision
  • the non-satellite positioning system is a WLAN positioning system.
  • the method includes obtaining satellite measurements from two satellites or three satellites.
  • the DOP is related to the angle between the two satellites with respect to the initial position estimate.
  • the method includes obtaining satellite measurements from three satellites.
  • the method includes grouping the three satellites into three groups of two satellites, determining an angle between each of the two satellites with respect to the initial position determination for each group, and selecting two or more satellites from the group of three satellites based on the angles measured, wherein satellites having large angles between them are selected and satellites having small angles in between them are not selected.
  • the DOP is related to an aggregate of the angles between each pair of three satellites with respect to the initial position estimate.
  • a large DOP corresponds to satellites that display poor geometry in reference to the location of the device and a large value of DOP can be 3.0.
  • a small DOP corresponds to satellites that display good geometry in reference to the location of the device and a small value of DOP can be a value between about 1.4 to about 2.5.
  • the initial position estimate is refined when the DOP is smaller than 1.65.
  • the hybrid positioning system constructs a satellite vector corresponding to a vector from the initial position to each satellite.
  • the DOP of a set of two satellites is determined using the dot product of the satellite position vectors for each satellite, wherein a small value of DOP comprises a value between 0 and 0.85 and a large value of DOP comprises a value greater than or equal to 0.86.
  • the method can include determining an initial position estimate of a device using a non-satellite positioning system, obtaining satellite measurements from three satellites, wherein the measurements include each satellite's position with respect to the initial position estimate, grouping the three satellites into three groups of two satellites, determining an angle between each of the two satellites with respect to the initial position determination for each group, and selecting two or more satellites from the group of three satellites based on the angles measured, wherein satellites having large angles between them are selected and satellites having small angles in between them are not selected.
  • the DOP is related to an aggregate of the angles between each pair of three satellites with respect to the initial position estimate.
  • the hybrid positioning system constructs a satellite vector corresponding to the vector from the initial position to each satellite.
  • the angle between each of the two satellites with respect to the initial position determination is the DOP for each group.
  • the non-satellite positioning system is a WLAN positioning system.
  • the method includes determining an initial position estimate of a device using a non-satellite positioning system, obtaining satellite measurements from three satellites, wherein the measurements include each satellite's position with respect to the initial position estimate, grouping the three satellites into three groups of two satellites, determining an angle between each of the two satellites with respect to the initial position determination for each group, wherein the angle is the DOP for each group; determining three intermediate positions for the device using each group of two satellites; weighting the three intermediate positions for the device using the DOP for each group of two satellites; and determining a final position of the device by averaging the weighted intermediated positions.
  • the non-satellite positioning system is a WLAN positioning system.
  • Figure 1 A illustrates a configuration of satellites that provides an accurate position determination, according to an embodiment of the present disclosure
  • Figure IB illustrates a configuration of satellites that provides an inaccurate position determination, according to an embodiment of the present disclosure
  • Figure 2 illustrates the spread of two satellites with respect to a receiver's location in a plane defined by the two satellites and the receiver's location, according to an embodiment of the present disclosure
  • Figure 3 illustrates the example of Figure 2 in a two dimensional plane and the respective angles, according to an embodiment of the present disclosure
  • Figure 4 illustrates poor satellite geometry with two satellites and shows a large region in which receiver could be located, according to an embodiment of the present disclosure
  • Figure 5 illustrates a three satellite embodiment and the respective DOP 2 values, according to an embodiment of the present disclosure
  • Figure 6 illustrates three satellites in 3D space, including their angles with respect to each axis, according to an embodiment of the present disclosure
  • Figure 7 illustrates the configuration of Figure 6 in 3D space where the first satellite is on the x-axis and the second satellite in on x-y plane, according to an embodiment of the present disclosure.
  • the present disclosure describes a new technique for a positioning system, which uses an initial estimated location (IEL) from a WLAN positioning system and SPS satellite information to assess the quality of set of SPS measurements or individual satellites to be used in a position determination.
  • the present disclosure also relates to evaluating the quality of set of satellite positioning system (SPS) measurements and to improving the quality of SPS location estimation by accepting/rejecting satellite information.
  • This system can be used when the receiver sees less than four satellites, for example, two or three satellites.
  • the disclosure describes a new method used to evaluate the dilution of precision (DOP) metric, when less than four satellites are visible.
  • DOP dilution of precision
  • the embodiments also utilize the geometry of visible satellites to decide if the current set of visible satellites (either two or three satellites) are appropriate to be used for positioning and consequently to improve the overall quality of estimate of the predicted location reported by positioning system.
  • the method relates the geometry of the visible satellites to the predicted location of the receiver when only two or three satellites are visible.
  • the phrase "geometry of satellites" is used to describe the geometry of visible satellite with respect to the estimated receiver location throughout this disclosure.
  • the DOP metric is a well-known metric in satellite positioning and is used to assess the quality of set of satellites that are used for location determination. In this disclosure, a method is described to assess the quality of set of satellites when the set has only two or three satellites and an initial position of the device.
  • the provided technique in the embodiments can improve the quality of the estimated location in an integrated WLAN-PS and SPS environment.
  • the final reported location can be one of the following;
  • the quality of estimate metric in the latter case should consider the aggregate measurements from both WiFi access points and satellites' range information and range position information.
  • the quality of estimate in an integrated WLAN-PS and SPS environments can include a combination of the quality of the WLAN-PS reported location and the dilution of precision (DOPo) of SPS when satellites are in range and their position information is available.
  • DOPo dilution of precision
  • SPS uses at least four satellites to estimate the inaccuracies of estimated receiver location. These inaccuracies include x,y,z coordinate inaccuracies as well as receiver clock time inaccuracies. If one of the parameters is estimated perfectly and does not have any inaccuracy it can be effectively excluded from the DOP estimation and a fewer number of satellites would be required to solve for receiver location and DOP calculation. In the case of hybrid positioning systems, prior knowledge of the receiver location can indicate if the system was able to estimate the clock bias correctly and hence clock bias inaccuracies do not exist. This leads us to disregard the time variations in G and disregard the last column consisting of - 1.
  • This disclosure describes a method to provide a DOP metric, referred to as DOP 2 , for the cases where only two satellites are visible to the receiver. In such cases, it also provides a means for accepting or rejecting a set of satellites to be used in a positioning system. Note that DOP 2 has different scale compared to traditional DOPo metric but it behaves similarly. Smaller values of DOP 2 indicate good satellite geometry and larger values of DOP 2 indicate bad satellite geometry.
  • DOP 3 determines another DOP metric, referred to as DOP 3 , for cases where only three satellites are visible to the receiver.
  • the invention describes a satellite selection method. This method also can be used to accept/reject the entire set of satellites to be used in a positioning system. Similar to the DOP 2 metric, the DOP 3 metric provides a means to indicate if geometry of satellite is usable for a positioning system.
  • the hybrid positioning system for example as WLAN Positioning System (WLAN-PS)
  • WLAN-PS WLAN Positioning System
  • IEL initial estimated location
  • SPS SPS is able to obtain range estimates and satellite information from these two satellites.
  • the following method is used to determine whether or not the hybrid positioning system will use the satellite measurements for the final location determination. If, through the following method, it is determined that the satellites will provide accurate position measurements, then the satellites can be used in conjunction with the WLAN positioning system to determine the position of a device.
  • the satellite data can be ignored and the position determination can be made solely using the WLAN positioning system information.
  • the geometry of only two satellites is related to the quality of the set of satellites.
  • the defined metric describing the quality of set of satellites, can be used to improve the estimated location using an aggregate of WiFi access points and satellites measurements. This provides a means to obtain a DOP-like metric, referred to herein as DOP 2 , for the cases where only two satellites are visible to the receiver.
  • DOP 2 a DOP-like metric
  • the range measurements from satellites can be used to both provide a better location estimation and to improve the overall quality of estimate of the receiver location reported by the positioning system (i.e. positioning system can be a hybrid positioning system which can refine the IEL by employing the range measurements from visible satellites).
  • the DOP-like metric indicates unfavorable satellite geometry, the satellite measurements can be discarded.
  • the position information of the satellites can be related to the quality of that set of satellites to be used in positioning system when only two satellites are visible by the receiver. In such cases, the system then has to decide if satellites are close to one another with respect to IEL. In the case of only two visible satellites, a good metric to measure the quality of the set of the satellites is the angle of the two satellites with respect to IEL. The DOP 2 metric, in case of two satellites, can be related to the angle between the satellites with respect to the initial estimated location.
  • a first satellite 210, a second satellite 220 and the IEL of receiver 230 define one plane 240.
  • the angle 250 between the satellites 210, 220 in normal XYZ coordinates.
  • it is not essential and the angle between the satellites with respect to IEL can easily be obtained following the described procedure.
  • Rotating the plane containing the two satellites and the IEL as illustrated in Fig. 2 will result in what is shown in Fig. 3 and we will continue with notation of Fig. 3.
  • the rotation of the plane reduces a 3-D problem to a 2-D problem and hence reduces variables and numbers used for the calculation.
  • the disclosed method uses the unit vectors connecting the IEL to each satellite and measures the angle between the satellites.
  • angle between two satellites refers to the measure of an angle between the satellites with respect to the IEL.
  • the hybrid positioning system had previously determined the IEL using a WLAN positioning system.
  • the hybrid positioning system then utilizes the satellite information from each of the two visible satellites.
  • the satellite information contains the XYZ position of each satellite and hence the positioning system can find the distance between the IEL and each satellite and then form the unit vector connecting the IEL to satellite position.
  • (x r , y r ) represent the receiver location in 2D plane
  • (x s ,y s ) represent the i th satellite position in the 2D plane
  • xi represents the angle between the x-axis and the first satellite 210
  • x 2 represents the angle between the x-axis and the second satellite 220.
  • the DOP 2 value can be extracted as which is
  • DOP 2 is large. Large values of DOP 2 demonstrate poor satellite geometry (i.e. satellites are close to one another or are collinear) and small values of DOP 2 indicate good satellite geometry.
  • DOP 2 in , which is the minimum for DOP 2 .
  • DOP 2 values that are above 3.0 indicate are too high and indicate a set of satellites with poor geometry. Therefore, a set of satellites with a DOP 2 greater than 3.0 are unreliable for positioning purposes.
  • the set of satellites can be used to obtain a better location and to improve the quality of estimate of the reported location. Otherwise, the satellites are too close to one another and their distance measurements are not completely uncorrected and hence can not be used for positioning receiver's location.
  • the DOP 2 threshold can be determined by
  • set of satellites can not be used for positioning.
  • ⁇ 1 and set of satellites can be used for positioning.
  • This method also provides a means for satellite selection in a hybrid positioning system. It allows the hybrid positioning system to either reject the current set of visible satellites, i.e. only uses WLAN-PS reported location, or accept the satellite information and range measurements to be used for hybrid positioning. If two satellites are relatively close to one another, their angle is not ⁇ , their range measurements will most likely provide a very large region in which the receiver could be located. Consequently, the location accuracy decreases, as receiver could be anywhere in the region. The concept is depicted in Fig. 4. Figure 4 depicts two satellites 210, 220 with a small angle 400 between them, and a large location region 420. In such cases, hybrid positioning system would choose not to use the satellite information and would rely solely on the WLAN positioning information.
  • DOP 2 is only function of the angle between the satellites and hence it is only necessary to obtain some information about that angle. It is computationally more efficient to use only the relative positions of the satellites (with respect to initial location) and calculate the DOP 2 metric (as opposed to calculating the angle between the satellites from the same vectors and then calculating the DOP 2 metric based on that angle).
  • the dot product between two normalized vectors represents the cosine value of the angle of those two vectors.
  • ⁇ p 2 is the new threshold.
  • ⁇ p l when we used equation in [0049] to determine if two satellites are close.
  • ⁇ p 2 when we use equation in [0054] to determine if satellites are close.
  • ⁇ 2 instead of performing an additional step (calculating the angle between the satellites) and comparing the results to ⁇ p l , we compare the product of the vectors to another threshold, ⁇ 2 . We then compare .
  • threshold , ⁇ p 2 to determine if the current set of two satellites can be used for positioning.
  • set of satellites can be used for positioning.
  • FIG. 5 depicts a three satellite constellation; including a first satellite 210, a second satellite 220, and a third satellite 500 all located above the receiver location 230.
  • DOP(Sl,S2) 530 refers to the angle between first satellite and second satellite
  • DOP(Sl,S3) 520 is the angle between the first satellite and third satellite
  • DOP(S2,S3) 510 is the angle between the second satellite and third satellite.
  • the three satellite embodiment proposes three different approaches to obtain the relationship geometry between the satellites and the IEL.
  • the first approach is similar to the case with two satellites: the positioning system obtains the angles between each pair of satellites, and based on the obtained angles it evaluates the quality of the satellite measurements.
  • the first approach yields a value DOP 3a .
  • the second approach is to use the position information of the satellites and form a DOP 3 matrix (similar to traditional DOP matrix in SPS systems).
  • the difference between the proposed matrix and traditional DOP matrix is the exclusion of the time inaccuracies from the DOP matrix (i.e. exclusion of the last column in the matrix, containing -1 for all satellites).
  • the approach then continues similar to the traditional DOP method.
  • the second approach yields a value DOP 3 b.
  • the third approach is to translate the problem into a trigonometric problem by transforming the individual elements of the DOP 3 matrix defined in the second approach to their equivalent trigonometric functions and simplifying the matrix.
  • the positioning system then relates the geometry of the visible satellites to the quality of set of satellites to be used in positioning system.
  • the third approach yields a value DOP 3c .
  • the positioning system can employ the measurements from these three satellites to refine the initial location and improve the quality of estimated location. Note that although the approaches are different in scale, they behave similarly.
  • the DOP 3 metrics obtained from these approaches indicate if the current set of three satellites is usable for positioning. All three approaches result in a DOP 3 metric (different from the DOP 3 matrix), which if sufficiently small, can indicate the geometry of satellites is good for positioning.
  • DOP 3a (DOP 2 (S l ,S 2 ),DOP 2 (S l , S 3 ),DOP 2 (S 2 , S 3 )) where DOP 2 (Si, S 2 ) represents the angle between Si and S 2 , DOP 2 (Si, S 3 ) represents the angle between Si and S 3 and DOP 2 (S 2 , S 3 ) represents the angle between S 2 and S3. If all the DOP 2 values were more than the threshold, we could use all the three satellites for positioning, otherwise, two satellites would be close to one another and at least one of them would have to be rejected for positioning.
  • the threshold for DOP 3a and its subset DOP 2 values can be different from the case of two satellites only. In this case, we can restrict the spread of the satellites differently and increase the angle threshold. For example, we can define the angle threshold, ⁇ 3 ° to be around
  • each individual DOP 2 value is compared against a new threshold.
  • the restriction on the angle between satellites can be less strict when we have three satellites in view. Generally, having three satellites can provide better location estimation than cases with two satellites.
  • the range of angles between satellites which are beneficial to hybrid positioning can be defined as angles between 35 degrees and 145 degrees.
  • the assigned weights in the above method can be related to DOP values of each pair of the three satellites. For example, if one of the methods described earlier to obtain the DOP values, we know that the 1.4 is the best DOP value that system can obtain and 5 is much worse value for DOP. Now, if with three satellite, we obtain three angles of
  • DOP 3a The calculation of DOP 3a is computationally simple and fast as it requires simple vector manipulations and comparison. However, it performs relatively less accurate as it only compares each pair of satellites and not all three of them simultaneously.
  • the second method of finding an alternative DOP 3 metric consists of matrix manipulations. Defining the unit vectors from IEL to each satellite, i.e. ,
  • DOP 3b is more accurate than DOP 3a as it uses all three satellites and their respective position to find a DOP 3 metric. However, it is computationally more expensive and more time consuming than DOP 3a as it requires considerably more vector manipulations. In applications where computational power is not limited and we can perform fast algebraic matrix
  • DOP 3 b is preferred.
  • the third method to find a DOP 3 value for the case of three satellites involves transforming the G matrix into trigonometric functions and simplifying the DOP 3c answer.
  • FIG. 6 illustrates the concept and different angles.
  • Figure 6 depicts a three satellite embodiment of the present teachings; including a first satellite 210, a second satellite 220, and a third satellite 500 all located above the receiver location 230.
  • a x represents the angle between the first satellite and x-axis of the Cartesian coordinates.
  • a 2 represents the angle between the first satellite and y-axis and a 3 represents the angle between the first satellite and z-axis.
  • ⁇ ⁇ represents the angle between the second satellite and x-axis
  • ⁇ 2 represents the angle between the second satellite and y-axis and
  • ⁇ 3 represents the angle between the second satellite and z-axis.
  • ⁇ ⁇ m ⁇ 2 , and ⁇ 3 represent the angles between the third satellite and x-axis, y-axis, and z-axis, respectively.
  • angles are between connecting line of each satellite and receiver location and x, y, and z axes.
  • the third satellite, 500 can be anywhere in the 3D space, as illustrated in Fig. 7.
  • Figure 7 depicts a three satellite embodiment of the present teachings; including a rotated first satellite 210, a rotated second satellite 220, a projected third satellite 500 all located above the receiver location 230.
  • a x which represents the angle between the first satellite and x-axis of the Cartesian coordinates is 0.
  • a 2 and a 3 are both 90 degrees as the rotated satellites lies on the x-axis.
  • ⁇ ⁇ and ⁇ 2 represents the angle between the rotated second satellite and x-axis and y-axis, respectively. Since the rotated second satellite is on the x-y plane, ⁇ 3 is 90 degrees. Similar to the previous case, ⁇ ⁇ , ⁇ 2 , and ⁇ 3 represent the angles between the third satellite and x-axis, y-axis, and z- axis, respectively.

Abstract

La présente invention concerne un procédé pour déterminer la position d'un dispositif dans un système de positionnement hybride. Le procédé comprend les étapes suivantes : détermination d'une estimation de position initiale d'un dispositif en utilisant un système de positionnement non satellitaire ; obtention des mesures satellitaires provenant de moins de quatre satellites, les mesures comprenant chaque position de satellite par rapport à l'estimation de position initiale ; détermination de l'atténuation de précision (DOP) en se basant sur les mesures satellitaires ; si le DOP est petit, affinage de l'estimation de position initiale en utilisant les mesures satellitaires ; si le DOP est grand, utilisation de l'estimation initiale comme estimation de position finale pour le dispositif. Le système de positionnement non satellitaire peut, en option, être un système de positionnement par réseau WLAN. Les mesures satellitaires obtenues peuvent, en option, provenir de deux ou trois satellites. L'invention concerne également un procédé de détermination de DOP avec moins de quatre satellites dans un système de positionnement hybride.
PCT/US2010/050742 2009-10-02 2010-09-29 Détermination de position dans un système de positionnement hybride en utilisant une mesure d'atténuation de précision WO2011041430A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US12/572,524 2009-10-02
US12/572,524 US8279114B2 (en) 2009-10-02 2009-10-02 Method of determining position in a hybrid positioning system using a dilution of precision metric
US12/572,516 2009-10-02
US12/572,516 US20110080318A1 (en) 2009-10-02 2009-10-02 Determining A Dilution of Precision Metric Using Two or Three GPS Satellites

Publications (1)

Publication Number Publication Date
WO2011041430A1 true WO2011041430A1 (fr) 2011-04-07

Family

ID=43826628

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US2010/050742 WO2011041430A1 (fr) 2009-10-02 2010-09-29 Détermination de position dans un système de positionnement hybride en utilisant une mesure d'atténuation de précision

Country Status (1)

Country Link
WO (1) WO2011041430A1 (fr)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8054219B2 (en) 2008-06-06 2011-11-08 Skyhook Wireless, Inc. Systems and methods for determining position using a WLAN-PS estimated position as an initial position in a hybrid positioning system
US8063820B2 (en) 2009-07-16 2011-11-22 Skyhook Wireless, Inc. Methods and systems for determining location using a hybrid satellite and WLAN positioning system by selecting the best SPS measurements
US8154454B2 (en) 2009-07-16 2012-04-10 Skyhook Wireless, Inc. Systems and methods for using a satellite positioning system to detect moved WLAN access points
US8890746B2 (en) 2010-11-03 2014-11-18 Skyhook Wireless, Inc. Method of and system for increasing the reliability and accuracy of location estimation in a hybrid positioning system
WO2019203678A1 (fr) * 2018-04-18 2019-10-24 Limited Liability Company "Topcon Positioning Systems" Utilisation de relaxation sdp pour l'optimisation de l'ensemble de satellites choisi pour le positionnement
GB2500971B (en) * 2012-03-30 2020-01-01 Qualcomm Technologies Int Ltd Method and Apparatus for synchronization and precise time computation for GNSS Receivers

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030011511A1 (en) * 1999-11-12 2003-01-16 King Thomas M. Method and apparatus for assisted GPS
US20050017898A1 (en) * 2003-06-03 2005-01-27 Koichiro Teranishi Positional information determining apparatus
US20070052583A1 (en) * 2005-09-08 2007-03-08 Topcon Gps, Llc Position determination using carrier phase measurements of satellite signals
US20080111737A1 (en) * 2006-11-15 2008-05-15 Motorola Inc. Method and system for hybrid location aiding for multi-mode devices

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030011511A1 (en) * 1999-11-12 2003-01-16 King Thomas M. Method and apparatus for assisted GPS
US20050017898A1 (en) * 2003-06-03 2005-01-27 Koichiro Teranishi Positional information determining apparatus
US20070052583A1 (en) * 2005-09-08 2007-03-08 Topcon Gps, Llc Position determination using carrier phase measurements of satellite signals
US20080111737A1 (en) * 2006-11-15 2008-05-15 Motorola Inc. Method and system for hybrid location aiding for multi-mode devices

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8130148B2 (en) 2008-06-06 2012-03-06 Skyhook Wireless, Inc. System and method for using a satellite positioning system to filter WLAN access points in a hybrid positioning system
US8054219B2 (en) 2008-06-06 2011-11-08 Skyhook Wireless, Inc. Systems and methods for determining position using a WLAN-PS estimated position as an initial position in a hybrid positioning system
US8089398B2 (en) 2008-06-06 2012-01-03 Skyhook Wireless, Inc. Methods and systems for stationary user detection in a hybrid positioning system
US8242960B2 (en) 2009-07-16 2012-08-14 Skyhook Wireless, Inc. Systems and methods for using a satellite positioning system to detect moved WLAN access points
US8154454B2 (en) 2009-07-16 2012-04-10 Skyhook Wireless, Inc. Systems and methods for using a satellite positioning system to detect moved WLAN access points
US8223074B2 (en) 2009-07-16 2012-07-17 Skyhook Wireless, Inc. Systems and methods for using a satellite positioning system to detect moved WLAN access points
US8063820B2 (en) 2009-07-16 2011-11-22 Skyhook Wireless, Inc. Methods and systems for determining location using a hybrid satellite and WLAN positioning system by selecting the best SPS measurements
US8284103B2 (en) 2009-07-16 2012-10-09 Skyhook Wireless, Inc. Systems and methods for using a satellite positioning system to detect moved WLAN access points
US8564481B2 (en) 2009-07-16 2013-10-22 Skyhook Wireless, Inc. Systems and methods for using a satellite positioning system to detect moved WLAN access points
US9013350B2 (en) 2009-07-16 2015-04-21 Skyhook Wireless, Inc. Systems and methods for using a satellite positioning system to detect moved WLAN access points
US10031237B2 (en) 2009-07-16 2018-07-24 Skyhook Wireless, Inc. Techniques for selecting SPS measurements to use in determining a final location estimate based on a WLAN-based location estimate
US8890746B2 (en) 2010-11-03 2014-11-18 Skyhook Wireless, Inc. Method of and system for increasing the reliability and accuracy of location estimation in a hybrid positioning system
GB2500971B (en) * 2012-03-30 2020-01-01 Qualcomm Technologies Int Ltd Method and Apparatus for synchronization and precise time computation for GNSS Receivers
WO2019203678A1 (fr) * 2018-04-18 2019-10-24 Limited Liability Company "Topcon Positioning Systems" Utilisation de relaxation sdp pour l'optimisation de l'ensemble de satellites choisi pour le positionnement
US11029413B1 (en) 2018-04-18 2021-06-08 Topcon Positioning Systems, Inc. Using SDP relaxation for optimization of the satellites set chosen for positioning

Similar Documents

Publication Publication Date Title
US8279114B2 (en) Method of determining position in a hybrid positioning system using a dilution of precision metric
US20110080318A1 (en) Determining A Dilution of Precision Metric Using Two or Three GPS Satellites
US10114123B2 (en) Accuracy and performance of the hybrid positioning system
US10031237B2 (en) Techniques for selecting SPS measurements to use in determining a final location estimate based on a WLAN-based location estimate
US8063820B2 (en) Methods and systems for determining location using a hybrid satellite and WLAN positioning system by selecting the best SPS measurements
Langley Dilution of precision
US8130148B2 (en) System and method for using a satellite positioning system to filter WLAN access points in a hybrid positioning system
US6445927B1 (en) Method and apparatus for calibrating base station locations and perceived time bias offsets in an assisted GPS transceiver
US8019539B2 (en) Navigation system with apparatus for detecting accuracy failures
JP2003518632A (ja) Ｇｐｓ地上ハイブリッド位置決定システム方程式に対する代数的解を決定する方法および装置
WO2011041430A1 (fr) Détermination de position dans un système de positionnement hybride en utilisant une mesure d'atténuation de précision
US20140145878A1 (en) Positioning systems
Quddus et al. Validation of map matching algorithms using high precision positioning with GPS
CN107807373A (zh) 基于移动智能终端的gnss高精度定位方法
CN114488228B (zh) 一种适用于动态载体平台的gnss多路径误差削弱方法
US7515104B2 (en) Structured array geolocation
JP5566599B2 (ja) 精度不良を検出する装置を備えるナビゲーションシステム
Chen et al. Dilution of position calculation for MS location improvement in wireless communication systems
Gioia et al. GGTO: Stability and Impact on Multi-constellation Positioning
Zhang et al. Ray-tracing Correction for GNSS Velocity Estimation using Doppler Frequency: A Feasibility Analysis
Sirbu et al. Exploiting differential correction in the future Lunar Satellite Navigation System
Simpson et al. Module C: Positioning Techniques
Li et al. Using two GPS satellites to improve WiFi positioning accuracy in urban canyons
Jyothi et al. Velocity Estimation Method Considering Doppler Effect and PSO Based Algorithm for Satellites Constellation IRNSS and GPS
Yun et al. Effects of weighting functions for reference receiver clock adjustment on GBAS performance

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 10821180

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 10821180

Country of ref document: EP

Kind code of ref document: A1