Gps Positioning Method and Gps Position Device

• US 20080231509A1
• Filed: 08/18/2005
• Published: 09/25/2008
• Est. Priority Date: 08/18/2005
• Status: Active Grant

• Current Assignee: Mitsubishi Electric Corporation
• Original Assignee: Mitsubishi Electric Corporation
• Inventors: Iwamoto, Takashi, Nagano, Takafumi
• Granted Patent: US 7,538,725 B2
• Time in Patent Office: Days
• US Class Current: 342/357.12
• CPC Class Codes: G01S 19/396 Determining accuracy or reliability of position or pseudorange measurements

Abstract

In the present invention, a conditional probability distribution function of received signal which is conditioned with a received signal amplitude (a), a pseudo range (p) and a navigation bit (b_m) which are unknown parameters is acquired from a GPS signal sample S2 on the basis of a condition defined by a working hypothesis set in a working hypothesis setting part WH(i) and then the conditional probability distribution function (P(R_m|a, p, b_m)) is marginalized with respect to the pseudo range (p) to acquire a marginal posterior probability distribution function (P(p|R_m, a)) in a step ST11. Finally acquired is a pseudo range dependent function in proportion to the marginal posterior probability distribution function (P(p|R_m, a)). Then, in a step ST12, a value of pseudo range (p) which gives the maximum value of pseudo range dependent function is determined as an estimated pseudo range.

Claims

1. A GPS positioning method for estimating a pseudo range from a GPS signal, comprising the steps of:

(a) acquiring a signal sample by receiving said GPS signal;

(b) acquiring a pseudo range dependent function which is a function of pseudo range in proportion to a marginal posterior probability distribution function of pseudo range from said signal sample on the basis of a condition defined by a predetermined working hypothesis; and

(c) determining a value of pseudo range which gives the maximum value of said pseudo range dependent function as an estimated pseudo range wherein

said pseudo range dependent function includes a hyperbolic cosine function.

2. The GPS positioning method according to claim 1, wherein

said pseudo range dependent function includes logarithmic function.

3. The GPS positioning method according to claim 1, wherein

said pseudo range dependent function includes an approximation function consisting of partial approximation functions corresponding to sections.

4. The GPS positioning method according to claim 1, wherein

said pseudo range dependent function includes a table approximation function which sets an input/output relation for each of one or more sections.

5. The GPS positioning method according to claim 1, wherein

said predetermined working hypothesis includes a plurality of working hypotheses on the basis of specifics of navigation bit boundary and frequency correction,

said pseudo range dependent function includes a plurality of pseudo range dependent functions corresponding to said plurality of working hypotheses,

said estimated pseudo range includes a plurality of estimated pseudo ranges, and

said step (c) includes a step of determining a value of pseudo range which gives the maximum value of each of said plurality of pseudo range dependent functions as the corresponding one of said plurality of estimated pseudo ranges,

said GPS positioning method further comprising the step of

(d) determining one of said plurality of estimated pseudo ranges whose corresponding pseudo range dependent function is optimal as an optimal estimated pseudo range.

6. A GPS positioning apparatus for estimating a pseudo range from a GPS signal, comprising:

a signal acquisition part for acquiring a signal sample by receiving said GPS signal; and

a signal processing part for determining an estimated pseudo range by performing signal processing on the basis of said signal sample,

wherein said signal processing part acquires a pseudo range dependent function which is a function of pseudo range in proportion to a marginal posterior probability distribution function of pseudo range from said signal sample on the basis of a condition defined by a predetermined working hypothesis, and determines a value of pseudo range which gives the maximum value of said pseudo range dependent function as an estimated pseudo range, wherein said pseudo range dependent function includes a hyperbolic cosine function.