WO2018166696A1 - Method and device for filtering received satellite navigation signals - Google Patents

Abstract

The invention relates to a method for filtering received satellite navigation signals for a mobile platform, the method comprising a determination step, a selection step and a provision step. In the determination step, a horizon line (102) is determined from one perspective (100) of the platform. In the selection step, satellites (118) arranged above the horizon line (102) are selected. In the provision step, the satellite navigation signals of the selected satellites (118) are provided.

Description

 Description title

 Method and device for filtering received

Satellite navigation signals

State of the art

The invention is based on a device or a method according to the preamble of the independent claims. The subject of the present invention is also a computer program.

EP 679902 Bl describes a method for the selection of signals from navigation satellites.

Disclosure of the invention

Against this background, with the approach presented here, a method for filtering received satellite navigation signals, a device that uses this method, a mobile platform, and finally a corresponding computer program according to the

Main claims presented. The measures listed in the dependent claims advantageous refinements and improvements of the independent claim device are possible.

An object in an environment of a receiver for signals from

Navigation satellites can transmit between one signal

Navigation satellites and the receiver to be arranged. Thus, the signal can not be received directly, but via reflections on the object and / or other objects. This creates a path that travels the signal between the navigation satellite and the receiver longer than the shortest possible route. At the receiver, a position can then only be calculated with an inaccuracy, as the receiver is apparently further away from the navigation satellite.

In order to reduce the inaccuracy, those signals can be discarded which can reach the receiver only via a reflection because an object is arranged between the receiver and the navigation satellite.

Those signals that reach the receiver without reflection can be used since there is no object between the receiver and the receiver

Navigation satellites is arranged.

In this case, an earliest reception time can be taken into account if the signal is received multiple times.

It is a method for filtering received

 Satellite navigation signals for a mobile platform, the method comprising the following steps:

Determining a horizon line from a perspective of the platform;

Selecting satellites located above the horizon line; and

Providing the satellite navigation signals of the selected satellites.

Under a satellite navigation signal, a signal of a

Navigation satellites are understood. The satellite navigation signal has a code phase and a carrier phase and represents at least one transmission time of the satellite navigation signal. From the transmission time and a reception time, a transit time of the satellite navigation signal can be determined. About a propagation speed of

Satellite navigation signal and the transit time can be calculated a distance between the navigation satellite and a receiver. The

Satellite navigation signal uniquely identifies the transmitting navigation satellite. A horizon line can be a boundary line between a visible edge of an object and the visible sky. A

Perspective can be a perspective from a current location of the mobile platform's receiver. The mobile platform may be, for example, a robot or a vehicle. A trajectory of the navigation satellite and a current position of the navigation satellite on the trajectory are known. The position can be viewed from the perspective. Navigation satellites that are not obscured by objects can be selected.

The horizon line can be made using at least one image from the

Perspective of the platform. The image may be, for example, a panoramic image. Objects around the platform are shown in the picture. Their outlines can be determined. Where an outline marks a transition between an object and the open sky, the part of the outline can be defined as a horizon line.

The satellites can be selected using satellite orbit information. The lane information may be from the memory of a

Satellite navigation device are read out. The web information can also be stored in a separate memory. By the railway information at any time a current position of the satellite is known.

The satellite navigation signals may be provided to a satellite navigation device to determine a position of the platform. The preselection allows the position to be determined with high accuracy, avoiding systematic errors due to the multipath reception of the satellite signals.

In the step of selecting, satellites can be selected that have a direct line of sight from the perspective. By the direct

Visual link, the satellite navigation signal can get to the receiver directly, without reflection / multipath propagation.

Further, in the step of providing, reflections of the satellite signals can be suppressed using a suppression algorithm. When a satellite navigation signal is received multiple times, the first Receiving time are taken into account, since the signal propagation time is the shortest via the direct path.

This method can be implemented, for example, in software or hardware or in a mixed form of software and hardware, for example in a control unit.

The approach presented here also provides a device which is designed to implement the steps of a variant of a method presented here

to implement, control or implement appropriate facilities. Also by this embodiment of the invention in the form of a device, the object underlying the invention can be solved quickly and efficiently.

For this purpose, the device may comprise at least one computing unit for processing signals or data, at least one memory unit for storing signals or data, at least one interface to a sensor or an actuator for reading sensor signals from the sensor or for outputting data or control signals to the sensor Actuator and / or at least one

Communication interface for reading or outputting data embedded in a communication protocol. The arithmetic unit may be, for example, a signal processor, a microcontroller or the like, wherein the memory unit may be a flash memory, an EEPROM or a magnetic memory unit. The communication interface can be designed to read or output data wirelessly and / or by line, wherein a communication interface that can read or output line-bound data, for example, electrically or optically read this data from a corresponding data transmission line or output in a corresponding data transmission line.

In the present case, a device can be understood as meaning an electrical device which processes sensor signals and outputs control and / or data signals in dependence thereon. The device may have an interface, which may be formed in hardware and / or software. In a hardware training, the interfaces, for example, part of a so-called system ASICs, which includes a variety of functions of the device. However, it is also possible that the interfaces are their own integrated circuits or at least partially consist of discrete components. In a software training, the interfaces may be software modules that are present, for example, on a microcontroller in addition to other software modules.

The device may include a camera adapted to detect the horizon line in an image. For example, the camera may have a fisheye lens and be oriented perpendicular to the sky. The camera can be integrated, for example, in an antenna housing. Further advantageous implementations of the device use the front camera, the

Reversing camera and / or the cameras of a multi-camera system in the vehicle. Furthermore, a mobile platform is provided with an antenna for receiving satellite navigation signals and a device according to the present invention

featured approach.

Also of advantage is a computer program product or computer program with program code which can be stored on a machine-readable carrier or storage medium such as a semiconductor memory, a hard disk memory or an optical memory and for carrying out, implementing and / or controlling the steps of the method according to one of the above

described embodiments, in particular when the program product or program is executed on a computer or a device.

Embodiments of the approach presented here are shown in the drawings and explained in more detail in the following description. It shows:

1 is a representation of a perspective of a mobile platform and a horizon line according to an embodiment;

2 is a block diagram of a mobile platform with a Vorrichtu

Filtering received satellite navigation signals according to a

Embodiment; 3 shows a representation of trajectories of navigation satellites;

4 shows a representation of an image from a perspective of a vehicle and a horizon line according to an exemplary embodiment; and

5 is a flow chart of a method of filtering received satellite navigation signals in accordance with one embodiment. In the following description of favorable embodiments of the present invention are for the in the various figures

represented and similar elements acting the same or similar

Reference numeral used, wherein a repeated description of these elements is omitted.

1 shows an illustration of a perspective 100 of a mobile platform and a horizon line 102 according to an exemplary embodiment. The perspective 100 is shown as a circular distorted all-round view. The perspective 100 is shown with a polar coordinate system. In other words, that is

Perspective presented as a hemispherical distorted 360 ° panorama. The

Perspective 100 is shown, for example, as an illustration by a fisheye lens directed vertically upwards. In the center of the perspective 100 an unobstructed sky area 104 is thus represented. Objects around the mobile platform restrict the view of the sky 104. Here, the view is limited for example by mountains 106, skyscrapers 108, a detached house 110 and a tree 112. A silhouette of the objects 106, 108, 110, 112 defines the horizon line 102. The horizon line 102 may also be referred to as a skyline. Trajectories 114 of navigation satellites 116, 118 are also from the

Perspective 100 of the mobile platform shown. The objects 106, 108, 110, 112 cover parts of the trajectories 114. Thus, satellites 116 are also obscured by the objects 106, 108, 110, 112. The other satellites 118 have a direct line of sight to the platform in the sky area 104. In the approach presented here, the objects 106, 108, 110, 112 are detected and the horizon line 102 is determined. The satellites 116, 118 transmit encoded navigation signals. A navigation signal is assigned by its code depending on one of the satellites 116, 118. The received navigation signals

identify theoretically from the perspective of 100 currently visible satellites

116, 118. The trajectories 114 of the satellites 116, 118 are known. The currently theoretically visible satellites 116, 118 are separated by the horizon line into invisible or hidden satellites 116 and visible satellites 118. To calculate the position of the platform, only the signals from the visible satellites 118 are used.

2 shows a block diagram of a mobile platform 200 having a device 202 for filtering received satellite navigation signals 204 according to one embodiment. The platform 200 is, for example, a vehicle or a mobile robot. The perspective shown in FIG. 1 is related, for example, to the platform 200. The satellite navigation signals 204 are received by an antenna 206 of the platform 200. In a navigation device 208 of the platform 200, a position 210 of the platform 200 is calculated. The satellite navigation signals 204 are coded. each

 Satellite navigation signal 204 is uniquely associated with a navigation satellite 116, 118. Thus, all navigation satellites 116, 118 are known from which a navigation signal 204 is received. For each satellite 116, 118 its trajectory 114 and its current position 212 is known and can be retrieved from a data memory of the navigation device 208.

The device 202 for filtering comprises a determination device 214, a selection device 216 and a delivery device 218. In the determination device 214, a horizon line 102 is determined from a perspective 100 of the platform 200. The perspective 100 is from an environment sensor

220 of the platform 200 provided. For example, the perspective 100 is provided by an image 220 of a wrap-around camera 222. As in FIG. 1, 100 objects obscure parts of the sky from the perspective, and thus also the positions 212 of the hidden satellites 116. The horizon line 102 separates hidden areas from unseen areas of the sky. The uncovered Satellites 118 are selected in the selector 216 when located above the horizon line 102. In the provisioning device 218, for determining the position 210, the satellite navigation signals 224 associated with the selection of the satellites 118 are made available to the navigation device 208.

A system 202 and a method for precise location in complex environments is presented. FIG. 3 shows a representation of trajectories 114 of navigation satellites. The

Trajectories 114 are orbits around the earth 300. The trajectories 114 are arranged in mutually tilted planes. On a trajectory 114 several navigation satellites are arranged one behind the other. From any point 302 of the earth 300 are theoretically simultaneously several

Navigation satellites visible. In the example shown, 12 navigation satellites are theoretically visible at the same time. In practice, a local horizon limits the number of visible navigation satellites.

GNSS (Global Navigation Satellite System) tracking is used in many products. GNSS standard receivers use the so-called

Code phase of the signal, with a position accuracy in the meter range is achieved. RTK receivers (Real Time Kinematics) additionally use the carrier phase of the signal and thus achieve a position accuracy in the centimeter range. However, the location accuracy of both types of receivers suffers greatly when there are no direct line of sight to the satellites. The

Signals are then only about reflections, such as

Receive house walls, which leads to the inaccurate determination of the signal delay and consequently to an inaccurate position determination. The error in positioning is composed of several factors. The error is due to multipath propagation, ie

Reflections in the inner city area, dominant. The

Multipath propagation effects in the receiver should be minimized.

For example, a special antenna can be used which receives only signal portions with a large elevation angle. This method fits but not to the building. Multipath signals can also be detected by means of algorithmics

In other words, FIG. 3 shows a typical constellation of positioning satellites with currently 12 satellites to which a direct visual connection to a locating unit exists at the point of intersection 302 at the intersection of the dashed lines without structural obstacles. In this case, the 12 transit time measurements or the corresponding pseudo-range information in the location unit can be used for an expected estimate of the receiver position with minimum variance.

To determine the position, the receiver requires the signals of at least four satellites. The satellites used can then be selected to form a favorable angle to each other in order to achieve the lowest possible error. The receiver can also detect shaded satellites at the low signal strength and discard them for position determination. Due to the evaluation of the video signal presented here, a distinction between directly received signal and reflected signal can be achieved even with strong reflections.

4 shows a representation of an image 220 from a perspective of a

Vehicle and a horizon line 102 according to an embodiment. The image 220 has been captured using a fisheye lens. The illustration substantially corresponds to the representation in FIG. 1. Here, the vehicle travels between high-rise buildings 108. The sky 104 is largely hidden by the skyscrapers 108. As in FIG. 3, theoretically 12

Navigation satellites 116, 118 visible. Practically, only the five

Navigation satellites 118 above the horizon line 102 on the free line of sight to the platform. Although navigation signals of the other satellites 116 can be received, they are corrupted by reflections on the high-rise buildings 108.

The approach presented here allows effective suppression of multi-path error factors in complex scenarios. A vehicle location in the inner city area or a robot location in courtyards can thereby can be achieved by selecting the satellites 118 used for the location and thus significantly increasing the availability of accurate location information. In the approach presented here, a video-based selection of

 Positioning satellites 118 to which there is a direct line-of-sight connection. As a result, only signal propagation time measurements are included in the position estimate of the positioning receiver, which does not lead to erroneous distance measurements between satellite 118 and receiver unit due to the reflection of obstacles 108 in the propagation path.

The method is with comparatively low computational complexity

Embedded video systems implementable. In contrast to

Signal processing methods aimed at mitigating the multi-path error influence, the method presented here has the potential to completely avoid multi-path error influences. For error effects due to ground reflections, effective shielding concepts are available.

FIG. 4 shows a fisheye video image 220 or camera image 220 of an inner city environment or of a location scenario

Skyscrapers 108 are shown, which in a large solid angle range prevent a direct line of sight to the receivable location satellites 116 and thus can lead to large errors of the location estimation. Of the 12 potentially receivable satellites 116, 118, only five satellites 118 have a direct line of sight to the locating unit.

Here, the video image 220 is supplemented by a horizon line 102, which with

Image processing methods robust and with high angular resolution, such as 25 pixels per degree, corresponding to 0.04 ° degrees per pixel can be determined without the use of subpixel methods. The resulting

Segmentation allows precise location based on the satellites 118 to which there is a direct line of sight. For registration of the satellites 116, 118 in the camera coordinate system used, a dynamic orientation estimation of the camera can take place, which in turn is robust

Image processing methods are available. The orientation estimate can be supported by an additional use of inertial sensors and leads to a system with high availability and robustness.

The approach presented here can be advantageously integrated into automotive systems and robotics systems. For example, the camera-based selection of satellites 118 used may be integrated into automated vehicles and service robots such as lawn mowers, agricultural robots, or logistics robots.

5 shows a flowchart of a method for filtering received satellite navigation signals in accordance with one embodiment. For example, the method may be performed on a device for filtering as shown in FIG. 2. The method comprises a step 500 of determining, a step 502 of selecting, and a step 504 of providing. In step 500 of the determination, a horizon line is determined from a perspective of a mobile platform. In step 502 of selecting, satellites above the horizon line are selected. In step 504 of providing, the satellite navigation signals of the selected satellites become further

Use provided.

If an exemplary embodiment comprises a "and / or" link between a first feature and a second feature, then this is to be read so that the embodiment according to one embodiment, both the first feature and the second feature and according to another embodiment either only first feature or only the second feature.

Claims

claims A method of filtering received satellite navigation signals (204) for a mobile platform (200), the method comprising the steps of: Determining (500) a horizon line (102) from a perspective (100) of the platform (200); Selecting (502) satellites (118) located above the horizon line (102); and Providing (504) the satellite navigation signals (224) of the selected satellites (118). 2. A method according to claim 1, wherein in step (500) of determining the horizon line (102) is determined using at least one image (220) from the perspective (100) of the platform (200). A method according to any one of the preceding claims, wherein in step (502) of selecting, the satellites (118) are selected using orbit information (114) of the satellites (116, 118). A method according to any one of the preceding claims, wherein in the step (504) of providing the satellite navigation signals (224) are provided to a satellite navigation device (208) to determine a position (210) of the platform (200). A method according to any one of the preceding claims, wherein in the step of (502) selecting, satellites (118) are selected to which there is a direct line of sight from the perspective (100). A method according to any one of the preceding claims, wherein in step (504) of providing further, reflections of the satellite signals (224) are suppressed using a suppression algorithm. Apparatus (202) arranged to execute steps of the method according to any one of the preceding claims in respective units. 8. Apparatus (202) according to claim 7, comprising a camera (222) adapted to detect the horizon line (102) in an image (220). Mobile platform (200) having an antenna (206) for receiving satellite navigation signals (204) and a device (202) according to one of claims 7 to 8. 10. Vehicle system of a motor vehicle, in particular navigation system, infotainment system, driver information system,  Driver assistance system or camera system, where the  Vehicle system, a device (202) according to one of  preceding claims. A computer program adapted to carry out the method according to any one of the preceding claims. 12. A machine-readable storage medium on which the computer program according to claim 11 is stored.