A positioning device

Field of the invention

The invention relates to a positioning device, and more particularly, to a method and arrangement for improving operation of a position detector that is arranged to operate on the basis of a received radio signal.

Background

A positioning device is equipped with a position detector that is able to create and process location-indicating data. The position detector is typically arranged to op- erate on the basis of radio signals received from satellites of a satellite based positioning system and/or from terrestrial radio stations. Examples of satellite based positioning systems are the US Global Positioning System (GPS), the European Galileo positioning system, and the Russian GLONASS navigation system. A positioning device receives radio transmissions from a number of satellites and/or ter- restrial radio stations and the position detector uses timing and other characteristics of the radio transmissions to calculate the location of the positioning device. The accuracy of positioning is a critical issue associated with a position detector. The accuracy of the positioning may suffer due to unintentional reasons like noise and unintentional variations in the timing of the radio transmissions from different satellites or terrestrial radio stations and also due to intentional reasons like for example an intentional jamming component that has been added to GPS- positioning signals because of political reasons. The accuracy of the positioning may suffer also due to atmospheric conditions and physical objects like e.g. tall buildings. For example, a GPS-positioning device may give a wandering position- ing result also in a situation in which the GPS-positioning device is stationary, i.e. not moving. The power consumption is another critical issue associated with a position detector. Reception of radio signals from satellites and/or from terrestrial radio stations and performing computational operations for creating location- indicating data on the basis of the received radio signals may cause a significant portion of the total power consumption of a positioning device. In a case in which the positioning device is a battery operated mobile positioning device the power consumption of the position detector may have a strong influence on a maximum service time between successive battery charging times.

Summary

An objective of the invention is to provide a novel method and a novel arrangement for improving operation of a position detector that is arranged to operate on the basis of a received radio signal. A further objective of the invention is to pro- vide a novel positioning device and a novel computer program product for a positioning device or arrangement.

An arrangement according to the invention for improving operation of a position detector arranged to create location-indicating data on the basis of a received radio signal comprises: - a motion sensor arranged to create motion-indicating data on the basis of a physical phenomenon associated with mechanical movement, said motion- indicating data expressing whether the position detector is moving, and

- a control unit arranged to control creation of the location-indicating data on the basis of said motion-indicating data. A method according to the invention for improving operation of a position detector arranged to create location-indicating data on the basis of a received radio signal comprises:

- creating motion-indicating data on the basis of a physical phenomenon associated with mechanical movement, said motion-indicating data express- ing whether the position detector is moving, and

- controlling creation of the location-indicating data on the basis of said motion-indicating data.

A positioning device according to the invention comprises:

- a position detector arranged to create location-indicating data on the basis of a received radio signal,

- a motion sensor arranged to create motion-indicating data on the basis of a physical phenomenon associated with mechanical movement, said motion- indicating data expressing whether the position detector is moving, and

- a control unit arranged to control creation of the location-indicating data on the basis of said motion-indicating data.

A computer program product according to the invention for improving operation of a position detector arranged to create location-indicating data on the basis of a received radio signal comprises computer program means for making a programmable control unit to control creation of the location-indicating data on the basis of motion-indicating data that expresses whether the position detector is moving or not.

The physical phenomenon associated with mechanical movement can be, for example, rotational movement of a wheel of a land vehicle, air pressure in a Pitot tube, water pressure in a Pitot tube, the inertia force acting on an element of an acceleration sensor, or the gyroscopic force acting on a gyroscope.

The motion-indicating data can be used for controlling the creation of the location- indicating data for example in the following ways:

- the position sensor is switched into a power-off state or into a power saving mode as a response to a situation in which the position detector is not mov- ing, and/or

- variations of the location-indicating data created by the position sensor are suppressed as a response to a situation in which the position detector is not moving, the location-indicating data can be e.g. low-pass filtered in order to suppress the variations and to obtain an average value of the location- indicating data in the situation in which the position detector is not moving.

Switching the position detector into the power-off state or into the power saving mode as a response to a situation in which the position detector is not moving reduces average power consumption of the position detector. Low-pass filtering of the location-indicating data as a response to a situation in which the position de- tector is not moving attenuates alternating components of instantaneous errors in the location-indicating data. Therefore, it is possible to report trips with more accurate trip start and trip end locations.

Various embodiments of the invention both as to constructions and to methods of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

The embodiments of the invention presented in this document are not to be interpreted to pose limitations to the applicability of the appended claims. The verb "to

comprise" is used in this document as an open limitation that does not exclude the existence of also unrecited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated.

Brief description of the figures Embodiments of the invention presented in the sense of examples and their advantages are explained in greater detail below with reference to the accompanying drawings, in which figure 1 shows a block diagram of an arrangement according to an embodiment of the invention for improving operation of a position detector arranged to create Io- cation-indicating data on the basis of a received radio signal, figure 2 shows a positioning device according to an embodiment of the invention, and figure 3 is a flow chart of a method according to an embodiment of the invention for improving operation of a position detector arranged to create location-indicating data on the basis of a received radio signal.

Detailed description of the embodiments

Figure 1 shows a block diagram of an arrangement according to an embodiment of the invention for improving operation of a position detector 101 that has been arranged to create location-indicating data 102 on the basis of a radio signal 103 re- ceived with a radio receiver 104. The radio signal 103 can be received from satellites of a satellite based positioning system and/or from terrestrial radio stations. A satellite based positioning system can be, for example, the US Global Positioning System (GPS), the European Galileo positioning system, or the Russian GLON- ASS navigation system. A position detector 101 receives radio transmissions from a number of satellites and/or terrestrial radio stations and uses timing and other characteristics of the radio transmissions to create the location-indicating data 102. The location-indicating data can express the current location of the position detector e.g. in the form of degrees, minutes, and seconds of latitude and longitude. Furthermore, the location-indicating data 102 can be arranged to express speed and/or acceleration and their directions. The speed and its direction can be obtained as a first time derivative a location vector and the acceleration and its direction can be obtained as a second time derivative of the location vector. The arrangement comprises a motion sensor 105 arranged to create motion-indicating

data 110 on the basis of a physical phenomenon associated with mechanical movement. The arrangement comprises a control unit 106 arranged to control creation of the location-indicating data 102 according to the motion-indicating data 110. The motion-indicating data is able to express whether the position detector 101 is moving or not. The location-indicating data can be, for example, displayed in a visual form on a display screen 108. The position detector 101 , the radio receiver 104, the motion sensor 105, the control unit 106, and the display screen 108 can be, for example, integrated into a single device. As another example, the display screen 108 and/or the control unit 106 can be located in a first device and the rest of the above-mentioned elements (101 , 104, 105, and possibly 106) can be located in a second device that has a data communication connection with the first device.

In an arrangement according to an embodiment of the invention the display screen 108 is a display of a separate mobile phone or a personal computer. The GSM SMS (Global System Mobile, Short Message Service) can be used for sending the location-indicating data 102 from the control unit 106 to the mobile phone or to a communication unit coupled to the personal computer.

In an arrangement according an embodiment of the invention the control unit 106 is arranged to switch the position detector 101 into a power-off state as a response to a situation in which said motion-indicating data expresses that the position detector is stationary, i.e. not moving. The control unit 106 can also be arranged to switch the radio receiver into a power-off state or into a power saving mode when the position detector is stationary.

In an arrangement according an embodiment of the invention the control unit 106 is arranged to switch the position detector 101 into a power saving mode as a response to a situation in which said motion-indicating data expresses that the position detector is stationary.

In an arrangement according an embodiment of the invention the control unit 106 is arranged to low-pass filter the location-indicating data 102 as a response to a situation in which said motion-indicating data expresses that the position detector is stationary, i.e. not moving. The low-pass filtering suppresses wandering and jittering of the location-indicating data 102 when the position detector is not moving. For example, a GPS-position detector tends sometimes to give a wandering and jittering positioning result in a situation in which the GPS-position detector is not moving, because a GPS-signal may contain an intentional jamming component

that has been added because of political reasons. Also unintentional disturbances and noise may cause wandering and jittering to the location-indicating data 102. Atmospheric conditions and physical objects, e.g. tall buildings, may also cause wandering and jittering to the location-indicating data 102. The low-pass filtering provides an average value of the location-indicating data in a situation in which the position detector is not moving. Therefore, a stationary location of the position detector can be obtained with an improved accuracy, because alternating components of instantaneous errors in the location-indicating data are attenuated.

In an arrangement according an embodiment of the invention the control unit 106 is arranged to freeze the location-indicating data 102 as a response to a situation in which said motion-indicating data expresses that the position detector is stationary, i.e. not moving. In other words, the control unit 106 is arranged, as a response to a situation in which the motion-indicating data 110 expresses that the position detector 101 is stationary, to keep the location-indicating data 102 in its latest value related to such a time period when the motion-indicating data expressed that the position detector is moving. In addition to the freezing of the location-indicating data, the control unit 106 can be also arranged to switch the position detector 101 and/or the radio receiver 104 into a power-off state or into a power saving mode when the position detector is not moving. In an arrangement according an embodiment of the invention the physical phenomenon associated with mechanical movement is a rotational movement of a wheel of a land vehicle. The motion sensor 105 is arranged to create the motion- indicating data 110 on the basis of the rotational movement.

In an arrangement according an embodiment of the invention the physical phe- nomenon associated with mechanical movement is air pressure in a Pitot tube. The motion sensor 105 is arranged to create the motion-indicating data 110 on the basis of the air pressure.

In an arrangement according an embodiment of the invention the physical phenomenon associated with mechanical movement is water pressure in a Pitot tube. The motion sensor 105 is arranged to create the motion-indicating data 110 on the basis of the water pressure.

In an arrangement according an embodiment of the invention the physical phenomenon associated with mechanical movement is the inertia force acting on an element of an acceleration sensor. The motion sensor 105 comprises an accelera-

tion sensor and an integrator circuitry arranged to create the motion-indicating data 110 substantially as a time integral of an output signal of the acceleration sensor. Using the time integral is based on the fact that speed that indicates motion is the time integral of acceleration. The acceleration sensor can be for exam- pie a pendulum sensor, a piezo-electronic sensor, or any other suitable device for detecting acceleration.

In an arrangement according an embodiment of the invention the motion sensor 105 comprises an acceleration sensor and the motion-indicating data 110 is substantially an output signal of the acceleration sensor. This kind of motion sensor is suitable for applications in which motion cannot practically be so smooth that speed would be a non-zero constant, i.e. acceleration would be zero during the motion. Therefore, the motion can be detected by monitoring the acceleration. For example, the speed of a walking human being and the speed of a moving car are practically not constant. The motion sensor 105 may comprise two or more acceleration sensors that are arranged to sense acceleration in different directions. The three spatial dimensions can be covered with three acceleration sensors.

In an arrangement according an embodiment of the invention the physical phenomenon associated with mechanical movement is the gyroscopic force acting on a gyroscope. The motion sensor 105 comprises a gyroscope and the motion- indicating data 110 is substantially an output signal of the gyroscope. The output signal of the gyroscope indicates changes in the orientation of the motion sensor 105. This kind of motion sensor is suitable for applications in which motion cannot practically be so smooth that the orientation of the motion sensor would be sub- stantially constant during the motion. Therefore, the motion can be detected by monitoring changes in the orientation of the motion sensor. For example, the orientation of a walking human being and the orientation of a moving car are practically not constant during motion.

The motion sensor 105 may comprise two or more gyroscopes that are arranged to sense changes in the orientation in different directions. The three spatial dimensions can be covered with two gyroscopes the rotational axes of which are perpendicular with respect to each other.

Figure 2 shows a positioning device 200 according to an embodiment of the invention. The positioning device 200 comprises a position detector 201 arranged to

create location-indicating data 202 on the basis of a radio signal 203. The radio signal 203 is received with a radio transceiver 204 (transmitter-receiver). The positioning device 200 comprises a motion sensor 205 arranged to create motion- indicating data 210 on the basis of a physical phenomenon associated with me- 5 chanical movement of the positioning device 200. The motion-indicating data is arranged to express whether the positioning device is moving. The positioning device 200 comprises a control unit 206 arranged to control creation of the location- indicating data according to the motion-indicating data. An indicator of the current location of the positioning device is communicated to a user of the positioning de- 10 vice with a display screen 208 arranged to display the location-indicating data. The location-indicating data may express the current location of the positioning device e.g. in the form of degrees, minutes, and seconds of latitude and longitude. The positioning device 200 comprises input means 207 that may comprise e.g. a keyboard. A block 211 represents other elements of the positioning device 200.

15 A positioning device according to an embodiment of the invention is a mobile phone. In this case the block 211 may represent a microphone, means for supporting data communication protocols, a speaker, etc.

A positioning device according to an embodiment of the invention is a mobile device that is energized with a battery element.

20 A positioning device according to an embodiment of the invention is a vehicle i mounted device. A speedometer of a vehicle can be arranged to operate as the motion sensor 205.

The control unit 206 can be a programmable control unit that has been arranged to control the creation of the location-indicating data 202 with the aid of a computer 25 program product according to an embodiment of the invention. The computer program product according to an embodiment of the invention comprises computer program means for making the programmable control unit 206 to control the creation of the location-indicating data 202 on the basis of the motion-indicating data 210.

30 The computer program means can be, for example, sub-routines and/or functions.

A computer program product according to an embodiment of the invention can be embodied in a computer readable medium. The computer readable medium can be, for example, an optical compact disk or an electronic memory device like a RAM (random access memory) or a ROM (read only memory).

Figure 3 is a flow chart of a method according to an embodiment of the invention for improving operation of a position detector arranged to create location-indicating data on the basis of a received radio signal. In phase 301 , motion-indicating data is created on the basis of a physical phenomenon associated with mechanical movement. The motion-indicating data is arranged to express whether the position detector is moving. In phase 302, creation of the location-indicating data is controlled according to the motion-indicating data.

In a method according to an embodiment of the invention the creation of the location-indicating data is controlled 302 by switching the position detector into a power-off state as a response to a situation in which the motion-indicating data expresses that the position detector is stationary, i.e. not moving.

In a method according to an embodiment of the invention the creation of the location-indicating data is controlled 302 by switching the position detector into a power saving mode as a response to a situation in which the motion-indicating data expresses that the position detector is stationary.

In a method according to an embodiment of the invention the creation of the location-indicating data is controlled 302 by low-pass filtering the location-indicating data as a response to a situation in which the motion-indicating data expresses that the position detector is stationary. In a method according to an embodiment of the invention the creation of the location-indicating data is controlled 302 by freezing the location-indicating data as a response to a situation in which the motion-indicating data expresses that the position detector is stationary. In other words, as a response to a situation in which the motion-indicating data expresses that the position detector is stationary, the loca- tion-indicating data is kept in its latest value related to such a time period when the motion-indicating data expressed that the position detector is moving. In addition to the freezing of the location-indicating data, the position detector can be switched into a power-off state or into a power saving mode when the position detector is not moving. In a method according to an embodiment of the invention the physical phenomenon associated with mechanical movement is a rotational movement of a wheel of a land vehicle and the motion-indicating data is created 301 on the basis of the rotational movement.

In a method according to an embodiment of the invention the physical phenomenon associated with mechanical movement is air pressure in a Pitot tube and the motion-indicating data is created 301 on the basis of the air pressure.

In a method according to an embodiment of the invention the physical phenome- non associated with mechanical movement is water pressure in a Pitot tube and the motion-indicating data is created 301 on the basis of the water pressure.

In a method according to an embodiment of the invention the physical phenomenon associated with mechanical movement is the inertia force acting on an element of an acceleration sensor and the motion-indicating data is created 301 on the basis of an output signal of the acceleration sensor.

In a method according to an embodiment of the invention the physical phenomenon associated with mechanical movement is the gyroscopic force acting on a gyroscope and the motion-indicating data is created 301 on the basis of an output signal of the gyroscope. While there have been shown and described and pointed out fundamental novel features of the invention as applied to embodiments thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices and methods described may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. The specific examples provided in the description given above should not be construed as limiting. Therefore, the invention is not limited merely to the embodiments described above, many variants being possible without departing from the scope of the inventive idea defined in the independent claims appended hereto.