DE102008024263B4 - Method for determining the quality of a GNSS navigation solution - Google Patents

Abstract

Method for determining the quality of a GNSS navigation solution, characterized in that, with respect to a GNSS receiver, two consecutive position solutions Pt-1 and Pt are determined at time t and t-1, respectively, and the vector Pt-1Pt is formed therefrom, and the velocity vector v (t) of the GNSS receiver, further calculating both the vertical angle αv and the horizontal angle αh between the vectors Pt-1Pt and v (t), and finally using as a measure of the quality of the GNSS navigation solution a quality indicator λQuality of said vertical angle αv and said horizontal angle αh.

Description

The invention relates to a method for determining the quality of a GNSS navigation solution.

From time immemorial, the challenge of spatial orientation and the reproducible description of places and paths exists. What was once solved by navigating with the help of stars can now be made easy for anyone with modern satellite navigation systems, so-called Global Navigation Satellite Systems, GNSS for short: Anywhere in the world with a clear view of the sky, at any time and in any weather the own position can be determined with a precision of few meters, and the required equipment is almost affordable for everyone.

Navigation via GNSS has become commonplace in recent years. There is hardly a middle-class automobile that is sold without a navigation unit. In addition, there are numerous providers of mobile navigation devices. At the same time, there are various approaches to extend the use of GNSS data beyond the original idea of pure positioning. Even today, GNSS data are also used for purposes other than mere positioning, such. B. to calculate the toll on German highways. The use for the calculation of city toll or - against the background of the current discussion of the greenhouse gas - of CO ₂ emissions levies on the basis of driving behavior is also planned. Another area of application is to assess contributions to car insurance based on driving behavior (pay-as-you-drive / PAYD), as investigated on behalf of the Norwegian government in 2004 in an experiment and already offered by insurance in the UK as a product becomes. These examples are less about determining the position than measuring the distance covered and dynamics on both motorways and urban areas.

These new application areas place high demands on the accuracy and reliability of GNSS data and the analyzes based on it. At the same time, there are particular challenges in the area of city driving, such as those that would occur in applications such as the collection of city tolls or emissions taxes. For example, there are narrow street canyons that severely limit distance measurement and positioning using GNSS receivers through reflection and shadowing of satellite signals. Another difficulty is the assessment of the quality of a GNSS navigation solution without additional sensors, ie. H. seemingly poor navigation solutions can have good accuracies and vice versa. Due to costs one tries to carry out the position determination and also the quality analysis with GNSS only data. The problem with GNSS only methods, however, is the high, rapidly changing correlation of the satellite signals, which makes realistic quality information very difficult in a few cases. Furthermore, the measurement method for speed and position determination is subject to systematic errors that keep the measurement result with a fault. These errors depend on local environment parameters of the GNSS receiver, such as: For example, the number of visible satellites, reflections from the satellite signals, etc. In situations with poor environmental parameters that adversely affect the accuracy of the GNSS navigation solution, there will be an increasing number of jumps and drifts in the calculated positions to the true position. Any postprocessing procedure which allows a maximum distance to the real position is potentially adversely affected by such positional errors (jumps and drifts of the position). The goal is to reduce the position error.

• – Laufzeitmessung der Satellitensignale vom Satelliten zum Empfänger (notwendig zur Positionsbestimmung)
• – Exakte Frequenzmessung (Dopplerverschiebung zur nominalen Satellitensignalfrequenz) des eintreffenden Satellitensignals (notwendig zur Extraktion der Daten aus dem Signal). Aus dieser Messung kann die Geschwindigkeit und Orientierung des GNSS Empfängers berechnet werden.

Each GNSS receiver performs two different measurements to calculate a navigation solution, the

• - transit time measurement of the satellite signals from the satellite to the receiver (necessary for position determination)
• - Exact frequency measurement (Doppler shift to the nominal satellite signal frequency) of the incoming satellite signal (necessary to extract the data from the signal). From this measurement, the speed and orientation of the GNSS receiver can be calculated.

As theoretical studies but also practical investigations show, transit time measurement and frequency measurement are subject to different systematic errors and local influences. H. both measured quantities and thus also your results position / orientation and speed are largely uncorrelated. This makes it possible to validate the respective individual measurements on the other measurement, but also to combine statements about navigation solution from both types of measurement.

As GNSS navigation solutions form the basis for the solution of further technical tasks (see, for example, the applications filed in parallel on the same day) German Patent Application 10 2008 024 264.0-52 "Motion detection or standstill detection based on GNSS navigation solutions" the same applicant, using the internal priority as German Patent Application 10 2009 014 060.3-52 ), it is desirable to obtain a technically sound statement about the quality of a GNSS navigation solution.

From the pamphlets US 2005/0 065 722 A1 . US 5 525998 US 6 643 587 B2 and "Introduction to Random Signals and Applied Kalman Filtering" by RG Brown and PYC Hwang (John Wiley & Sons, Inc., 1997) discloses GPS based navigation techniques. In particular, from the US 2005/0 065 722 A1 a method for determining the quality of a GNSS navigation solution is known in which from speed measurement and position measurement as a function of time in each case a distance is calculated. Further, according to the US 2005/0 065 722 A1 calculates the difference of these distances, in order finally to measure the quality of the navigation data.

The filed on 19 March 2008 and on 5 November 2009 as DE 10 2008 015 107 A1 Published German Patent Application describes a method for determining the quality of a data from a navigation module, in particular from a GNSS receiver, determined and navigation data, in particular location coordinates, containing record, wherein the navigation module, the calculated position data together with other data as a navigation solution in the data set for further processing using the available navigation solution for location determination, whereby the data set of a navigation solution is tested for its quality in itself or in relation to the data set (s) of previous or following navigation solutions, whereby a data record evaluated as being defective is retained; and wherein a record evaluated as error-free is provided as a secure navigation solution for further processing.

The object of the invention is to provide a further method for determining the quality of a GNSS navigation solution or a further method for determining the quality of a data set containing navigation data determined by a navigation module. In addition, a use of these methods should be specified.

According to the invention, this object is achieved by a method according to claim 1, by a method according to claim 10 and by a use according to claim 25.

Advantageous and preferred developments of the method according to the invention according to claim 1 are the subject matter of claims 2 to 9 and 22 to 24.

Advantageous and preferred developments of the method according to the invention according to claim 10 are subject matter of claims 11 to 24.

For the use according to the invention specified in claim 25, reference is expressly made to the German patent application filed in parallel by the same Applicant on the same day 10 2008 024 264.0-52 "Procedure for the detection of movement or standstill based on GNSS navigation solutions", claiming the inner priority as a German patent application 10 2009 014 060.3-52 was continued. The methods described in the present patent application are particularly suitable as a supplementary and accuracy-enhancing component of the methods for detecting motion or standstill described in that patent application on the basis of GNSS navigation solutions.

Advantageous and preferred embodiments of the method according to the invention are explained below with reference to figures. It shows:

1 schematically an angle between position sequence and velocity vector in 2D and

2 schematically the angle between position sequence and velocity vector in 3D.

Given is a sequence of two consecutive GNSS navigation solutions (position, orientation and velocity) calculated in the usual way from measurement results.

The idea underlying the method according to the invention in the particular embodiment described below is to calculate the calculated direction of movement from two consecutive position solutions P _t-1 and P _t at time t or t-1, with the calculated orientation and speed v _t from the Doppler measurement (frequency measurement ) to compare. It compares the direction of movement and happens over the angle between the vectors v (t) and P _t-1 P _t (cf. 1 ). The horizontal angle α _h and the vertical angle α _{v are} distinguished. The horizontal angle α _h is the angle α when the vectors v (t) and P _t-1 P _{t are} projected into the horizontal plane. The vertical angle α _v is the angle α when the vectors v (t) and P _t-1 P _{t are} projected into the vertical plane. The vertical plane is spanned by v (t) and the projection of v (t) into the horizontal plane.

wobei Δt dem Zeitintervall zwischen den Zeitpunkten t und t – 1 in Sekunden entspricht. Alternativ kann der Geschwindigkeitswert für „Geschwindigkeit über Grund” verwendet werden. In diesem Fall liegt der Vektor v(t) planar in der Ebene (Erdoberfläche) und hat keine Höhenkomponente.The vector v (t) is calculated using the velocity values in x, y, and z direction:

where Δt corresponds to the time interval between times t and t-1 in seconds. Alternatively, the speed over ground speed value can be used. In this case, the vector v (t) lies planar in the plane (earth surface) and has no height component.

The vector P _t-1 P _t is the vector from the position solution P _t-1 to the position solution P _t . Schematically, the vectors and included angle are in 1 shown.

The included angle α between two vectors v (t) and P _t-1 P _t can be calculated via the scalar product:

For the quality indicator, the horizontal angle α _h and the vertical angle α _{v are} distinguished (cf. 2 ). Since a vehicle is usually moved on the ground and not in the air, the horizontal position is more important than the vertical position when specifying a position on a map. Therefore, GNSS receivers use a satellite constellation that has a higher accuracy for the horizontal position than for the vertical position. The vertical angle α _v is subject to a larger error than the horizontal angle α _h .

The indicator for the present dynamics and thus the quality of the navigation solution is defined as a function of the size of the included angle between the vectors of the position sequence (from two temporally following positions) and the velocity vector (from speed amount and orientation).

Consider the included angle between the two vectors, i. H. at angles α greater than 180 ° is assumed as angle α = 360 ° - α.

At standstill, the angle α spreads arbitrarily (<180 °), with moving receivers, the angle α is smaller with good GNSS navigation solution than with a poor GNSS navigation solution. Ideally, the angle α = 0 °, worst case α = 180 °. The possible values for 0 ° <α <180 ° are used as parameters in the quality determination.

For the quality indicator, the horizontal angle α _h and the vertical angle α _{v are} distinguished. The possible values for 0 ° <α _h , α _v <180 ° are used as parameters in the quality determination. Since the velocity vector is horizontal, α _v corresponds to the angle between the horizontal and the connection vector from two consecutive positions. For α _v it is checked whether the angle exceeds a threshold value α _th and also takes the result into account in the quality indicator.

mit:
ω_αh = Gewichtung für α_h,
ω_αv = Gewichtung für α_v,
ω_αh + ω_αv = 1,
α_th = Schwellwert für α_v The quality indicator of a GNSS navigation solution can be calculated as follows:

With:
ω _αh = weighting for α _h ,
ω _αv = weighting for α _v ,
ω _αh + ω _αv = 1,
α _th = threshold for α _v

The larger the value λ, the better the quality of the GNSS position solution. Optionally, a threshold λ _Thresh can be used for λ, which defines the boundary between good and bad GNSS position solution.

In one embodiment of the method according to the invention z. For example: α _th = 10 degrees ω _αh = 0.5 ω _αv = 0.5

An example of a lower-quality GNSS position solution is then z. B. Measured values for α _h and α _v : α _h = 35 degrees α _v = 12 degrees ⇒ λ _Quality (35,12) = 0.5 · (180 - 35/180) + 0.5 · 0 = 0.403

An example of a better quality GNSS position solution would be z. B. Measured values for α _h and α _v : α _h = 5 degrees α _v = 3 degrees ⇒ λ _Quality (5,13) = 0.5 · (180 - 5/180) + 0.5 · (10 - 3/10) = 0.836

Claims (25)

Method for determining the quality of a GNSS navigation solution, characterized in that, with respect to a GNSS receiver, two consecutive position solutions P _t-1 and P _{t are determined} at the time t and t-1, respectively, and the vector P _t-1 P _{t is} formed therefrom Further, as the velocity vector v (t) of the GNSS receiver is determined, further, both the vertical angle α _v and the horizontal angle α _h between the vectors P _t-1 P _t and v (t) are calculated and finally a measure of the quality of the GNSS navigation solution a quality indicator λ _{Quality is} calculated using said vertical angle α _v and said horizontal angle α _h . Method according to claim 1, characterized in that the quality indicator λ _Quality is calculated as follows:

with: ω _αh = weighting for α _h , ω _αv = weighting for α _v , ω _αh + ω _αv = 1, α _th = threshold value for α _v Method according to one of the preceding claims, characterized in that the velocity vector v (t) is calculated over the velocity values in x, y, and z-direction:

where Δt corresponds to the time interval between times t and t-1 in seconds. Method according to claim 1 or claim 2, characterized in that the velocity over ground is used as the velocity vector v (t). Method according to one of the preceding claims, characterized in that a navigation solution is assessed as error-free if the quality indicator λ _Quality exceeds a certain threshold λ _Thresh , and that the navigation solution is otherwise assessed as faulty. A method according to claim 5, characterized in that the threshold λ _{Thresh is} configurable. A method according to claim 5 or claim 6, characterized in that a evaluated as error-free navigation solution is provided for further processing. Method according to one of Claims 5 to 7, characterized in that a navigation solution evaluated as error-free is temporarily buffered in a buffer for correction as incorrectly evaluated navigation solutions. Method according to one of Claims 5 to 8, characterized in that a navigation solution assessed as faulty is retained insofar as it is either discarded or buffered for the purpose of correction in a buffer, the navigation solution initially assessed as faulty and subsequently corrected as a secured navigation solution is provided for further processing. Method for determining the quality of a data set containing a navigation module, in particular a GNSS receiver, and containing navigation data, in particular location coordinates, the navigation module providing the calculated position data together with other data as navigation solution in the data record for further processing, wherein the available navigation solution is used to determine the location, wherein the record of a navigation solution is tested in itself or in relation to the one or more records of previous or following navigation solutions on its quality, with a bad rated as data set is retained, and one as error-free is provided as a secure navigation solution for further processing, characterized in that the comparison of the angle of a position of orientation and speed of the GNSS receiver and the is calculated from the transit times of the satellite signals calculated position and thereby horizontal and vertical proportions are considered separately. A method according to claim 10, characterized in that a evaluated as error-free data set is temporarily stored in a buffer for correction as incorrectly evaluated records. Method according to claim 10 or claim 11, characterized in that a data record evaluated as being defective is retained insofar as it is either discarded or temporarily stored in a buffer for the purpose of correction, whereby a data record initially evaluated as erroneous and subsequently corrected as a data record Navigation solution is provided for further processing. Method according to one of claims 10 to 12, characterized in that the position and / or the speed and / or the heading and / or the satellite geometry are used in the calculation for determining quality indicators of a navigation solution. Method according to one of claims 10 to 13, characterized in that the quality indicator and / or the overall quality is determined stepwise and normalized to a value between 0 (bad) and 1 (excellent). Method according to one of claims 10 to 14, characterized in that the determination of the quality of the navigation solution via two or more, consecutive GNSS navigation solutions. Method according to one of claims 10 to 15, characterized in that the determination of the quality of the navigation solution via two or more, consecutive GNSS navigation solutions is determined, which do not follow each other directly in time to ignore temporary inconsistencies in the GNSS navigation solutions can. Method according to one of claims 10 to 16, characterized in that the determination of the quality of the navigation solution via configurable thresholds takes place. Method according to one of claims 10 to 17, characterized in that the determination of the quality of the navigation solution over N temporally past navigation data sets is determined dynamically. Method according to one of claims 10 to 18, characterized in that the comparison of the angle of a position of orientation and speed of the GNSS receiver and the position calculated from the transit times of the satellite signals is used. Method according to one of claims 10 to 19, characterized in that the angle between the horizontal plane and the orientation for determining the quality of the navigation solution is used. Method according to one of claims 10 to 20, characterized in that the orientation and speed of the GNSS receiver from the Doppler measurement of the GNSS signals and the position of the GNSS receiver are calculated from the transit times of the GNSS signals. Method according to one of the preceding claims, characterized in that all threshold values for the assessment of the quality of the navigation solution are selected statically depending on the quality of the GNSS environment, the quality of the GNSS environment describing the expected quality of the GNSS navigation parameters based on local environmental parameters. Method according to one of claims 1 to 21, characterized in that at least one threshold for the calculation of the quality of the navigation solution depending on the quality of the GNSS environment is dynamically calculated. A method according to claim 23, characterized in that all threshold values for the assessment of the quality of the navigation solution are dynamically calculated as a function of the quality of the GNSS environment. Use of the method according to one of the preceding claims as part of a method for detecting movement or standstill based on GNSS navigation solutions, wherein an indicator is calculated for each or selected GNSS navigation information, via which the quality of the navigation solution can be determined.

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