JP2004233186A - Portable navigation system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a navigation system capable of easily acquiring high positioning accuracy at hybrid navigation in a portable navigation system also capable of GPS navigation. <P>SOLUTION: The portable hybrid navigation is provided with a GPS reception means for receiving radio waves from GPS satellites and outputting positioning information on a present position on the basis of a prescribed threshold value, a detection part for detecting the present position as to whether an autonomous navigation part for detecting the present position on the basis of a travel distance and/or a direction is connected or not, and a threshold value altering means for altering the threshold value on the basis of the output of the detection part. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a portable navigation device.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in a navigation device dedicated to a vehicle, an autonomous navigation that calculates a traveling distance from a vehicle speed sensor or the like, detects an absolute direction from a direction sensor such as a gyro to detect a current position, and transmits a radio wave from a GPS (Global Positioning System) satellite. A hybrid navigation system of hybrid navigation combining a GPS that receives and detects a current position has been considered (for example, Patent Document 1). The hybrid navigation system described above estimates the current position by autonomous navigation and corrects the position by GPS, so high position accuracy can be achieved even in places where there are tall buildings in tunnels or surrounding areas where radio waves from GPS satellites cannot be received. can get.
[0003]
In recent years, portable navigation devices have been marketed. This portable navigation device detects the current position by GPS so that the position can be detected even when the device is carried.
[0004]
Further, a portable hybrid navigation device that is the above-described hybrid navigation when mounted on a vehicle is also considered. This portable hybrid navigation device detects the position by GPS when carrying, connects the vehicle speed sensor and direction sensor mounted on the car to the navigation device when mounted, and detects the current position from the output of the vehicle speed sensor and direction sensor. Then, the position is corrected by the GPS.
[0005]
[Patent Document 1]
JP-A-8-178681 (page 3-4, FIG. 1)
[0006]
[Problems to be solved by the invention]
However, in the above-described portable hybrid navigation device, it is necessary to always display the current position so that the user can grasp the current position at any time. Hereafter, this setting is given priority. As a result, position correction is performed with GPS having low position accuracy even during hybrid operation, and it has been difficult to always achieve high position accuracy regardless of the hybrid navigation device. Further, it has been very difficult to set such that both the position accuracy and the positioning rate are compatible.
[0007]
SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a portable navigation device capable of performing GPS navigation, which can easily obtain high positional accuracy during hybrid navigation.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, in a portable navigation device according to the present invention, a GPS receiving means for receiving a radio wave from a GPS satellite and outputting position information of a current position based on a predetermined set value, a traveling distance and / or A detection unit for detecting whether or not an autonomous navigation unit for detecting the current position based on the azimuth is connected, and a set value changing unit for changing the set value based on an output of the detection unit.
[0009]
A GPS receiver for receiving a radio wave from a GPS satellite and outputting position information of a current position based on a predetermined set value; a storage unit for storing the first set value and the second set value; A detection unit that detects whether or not an autonomous navigation unit that detects a current position based on a distance and / or an azimuth is connected; and, when the detection unit detects that the autonomous navigation unit is connected, the second 1 is read out from the storage unit and output to the GPS receiving unit. When it is detected that the autonomous navigation unit is not connected, the second set value is read out from the storage unit and the GPS reception unit is read out. Setting change means for outputting to the means.
[0010]
Further, the first set value is a set value giving priority to position accuracy, and the second set value is a set value giving priority to positioning rate.
[0011]
The set value is at least one of an S / N value, a DOP value, an elevation angle value, and whether or not two-dimensional positioning is possible.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to the drawings.
[0013]
FIG. 1 is a block diagram showing a configuration of a main part of the embodiment. In the portable navigation device (1), a control circuit (2) controls each section based on a program written in a ROM (3). In the ROM (3), in addition to the program, a threshold value of a parameter for a GPS receiver (4) described later to measure a current position is also written. The GPS receiver (4) receives a radio wave from a GPS satellite, measures a current position based on a threshold of a predetermined parameter described later, and outputs measurement data to the control circuit (2). Reference numeral (5) denotes a map reproducing unit which reads map information from the DVD on which the map information is written and outputs the map information to the control circuit (2). The display unit (6) is a liquid crystal monitor, and displays a map and a current position under the control of the control circuit (2). The external input terminal (7) performs an input of the autonomous navigation unit (8). The autonomous navigation unit (8) has a jack, and is electrically connected to the control circuit (2) by connecting the jack to the external connection terminal (7). An autonomous navigation unit (8) measures a current position based on an output of a direction sensor (9) for detecting an absolute direction and an output of a vehicle speed sensor (10) for detecting a traveling distance, and transmits the measured data to a control circuit (2). Output to
[0014]
Here, the parameters for the GPS receiver (4) to detect the current position and output the measurement data to the control circuit (2) will be described. The GPS receiver (4) has four parameters for measuring the current position and outputting measurement data to the control circuit (2): S / N value, DOP value, elevation angle, and two-dimensional positioning availability. ing.
[0015]
The S / N value is a value representing the electric field strength of a radio wave received from a GPS satellite. The electric field strength varies depending on the distance from the GPS satellite and obstacles such as clouds in the sky. Since the position can be detected more accurately when the electric field strength of the received radio wave is larger, a threshold value is set so that data of a GPS satellite whose S / N value of the radio wave received from the GPS satellite is less than a predetermined value is not used for position detection. . If a threshold value is provided where the S / N value is large, the position accuracy that can be detected is improved, but the number of GPS satellites that can be used for position detection decreases.
[0016]
The DOP value is a numerical value of the arrangement position of a plurality of GPS satellites used for measuring the current position. For example, when the current position is detected using three or more GPS satellites, the plurality of GPS satellites are used. In the case where the current position is detected using two GPS satellites or the distance between the two GPS satellites, the current position is quantified. The larger the DOP value, the more accurate the position detection. FIG. 2A is a diagram conceptually and three-dimensionally showing the position of a car equipped with the portable navigation device (1) and a GPS satellite, and FIG. 2B is a conceptual diagram of FIG. It is. In FIG. 2A, solid circles indicate visible GPS satellites, broken circles indicate visible GPS satellites, and triangles indicate cars. Since the detection of the current position is obtained by triangulation from the position of the GPS satellite, in FIG. 2, the current position is measured from, for example, the positional relationship of three GPS satellites (25), (26), and (27). It is more accurate to measure the current position (large DOP value) from the positional relationship of the three GPS satellites (21), (24), and (28) than to (DOP value small) because the GPS satellites are dispersed. The current position can be detected. When the DOP value is equal to or less than the predetermined value, a threshold value is provided so that the measurement data is not output to the control circuit (2). If a threshold value is provided at a place where the DOP value is large, for example, when traveling on a mountainside or the like, since only radio waves from GPS satellites located in a deviated direction can be received, the DOP value becomes smaller than the threshold value and the control circuit (2) Measurement data cannot be output.
[0017]
The elevation value is a numerical value of an angle formed between a plurality of satellites used for detecting the current position and the portable navigation device (1). In FIG. 2, for example, the GPS satellites (20), (24), and (28) are used instead of measuring the current position based on the positional relationship of three GPS satellites (22), (24), and (27) (small elevation angle). Measuring the current position from the positional relationship between the three GPS satellites (higher elevation angle) allows more accurate position detection. A threshold value is provided so that the measured data is not output to the control circuit (2) when the elevation angle value is equal to or less than a predetermined value. If a threshold value is provided at a place where the elevation value is large, for example, when traveling in an urban area or a mountain area where tall buildings are lined up, only the radio waves of the GPS satellites located directly above can be received, so the elevation value becomes smaller than the threshold value. Measurement data cannot be output to (2).
[0018]
The two-dimensional positioning availability is a set value of whether to output the current position detected by the two-dimensional positioning to the control circuit (2). Two-dimensional positioning requires reception of radio waves from at least two or more GPS satellites, and three-dimensional positioning requires reception of radio waves from at least three or more GPS satellites. In the case of three-dimensional positioning, since the height and the like can be obtained, for example, the current position can be obtained from either an elevated expressway or a general road parallel to and below the expressway. However, when two-dimensional positioning is set not to be performed, for example, when the number of GPS satellites whose S / N value exceeds the threshold is two, the measured value of the current position is output to the control circuit (2). Can not.
[0019]
The values obtained by reducing the above-described threshold values are written in the ROM (3) as the threshold values for the GPS navigation, and the values obtained by increasing the respective threshold values are stored as the threshold value in the hybrid navigation.
[0020]
Next, the operation of the embodiment of the present invention will be described.
[0021]
FIG. 3 is a flowchart showing the operation of the control circuit (2) of the portable navigation device (1).
[0022]
The control circuit (2) detects whether or not the autonomous navigation unit (8) is connected to the external input terminal (7) by detecting insertion of a jack into the external input terminal (7) (S1).
[0023]
When detecting that the autonomous navigation unit (8) is connected (Y in S1), the control circuit (2) reads the threshold value at the time of self-contained navigation written in the ROM (3) and reads the threshold value in the GPS receiving unit (4). Output (S2). Then, the current position input from the autonomous navigation unit (8) is displayed on the display unit (6) together with the map information input from the map reproduction unit (5) (S3). Thereafter, the control circuit (2) measures the time by a timer (not shown) provided therein (S4), and when a predetermined time has elapsed (Y in S4), an input from the GPS receiver (4) is made. It detects whether there is. If there is no input from the GPS receiver (4) (N in S5), the process returns to S1. In step S5, the GPS receiver (4) detects the current position using the threshold value during autonomous navigation, and when the current position is input to the control circuit (2), the control circuit displays the result as the current position on the display unit (6). I do.
[0024]
If it is not detected in S1 that the autonomous navigation unit (8) is connected (N in S1), the control circuit (2) reads the GPS navigation threshold value written in the ROM (3) and receives the GPS signal. Output to the section (4) (S7). The GPS receiver (4) detects the current position based on the input threshold. When the current position is detected by the GPS receiving unit (4) and input to the control circuit (2) (Y in S8), the control circuit (2) displays the input current position in the map reproducing unit (5). It is displayed on the display unit (6) together with the input map information (S9).
[0025]
In this embodiment, the GPS receiver (4) determines whether to use the received GPS information as the current position information based on the threshold, but the GPS receiver (4) controls the received GPS information as it is. The information may be output to the circuit (2), and the control circuit (2) may determine whether to use the GPS information input from the GPS receiver (4) as the current position information based on the threshold.
[0026]
【The invention's effect】
According to the present invention, the threshold value for detecting the current position of the GPS receiving unit is changed between the time of the GPS navigation and the time of the hybrid navigation, so that the current position can be corrected with high position accuracy during the hybrid navigation.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a main part of a portable navigation device according to the present invention.
FIG. 2 is a diagram conceptually showing the positions of a car equipped with the portable navigation device (1) of the present invention and a GPS satellite.
FIG. 3 is a flowchart showing an operation of a main part of the portable navigation device of the present invention.
[Explanation of symbols]
1 portable navigation device 2 control circuit 3 ROM
4 GPS receiving unit 5 Map reproducing means 6 Display unit 7 External input terminal 8 Autonomous navigation unit

Claims (5)

It is determined whether or not a GPS receiving unit that receives a radio wave from a GPS satellite and outputs position information of a current position based on a predetermined threshold value and an autonomous navigation unit that detects a current position based on a traveling distance and / or an azimuth are connected. A portable navigation device, comprising: a detecting unit for detecting; and a threshold changing unit for changing the threshold based on an output of the detecting unit. GPS receiving means for receiving radio waves from GPS satellites and outputting position information of the current position based on a predetermined threshold value, storage means for storing the first threshold value and the second threshold value, travel distance and / or azimuth A detection unit that detects whether an autonomous navigation unit that detects the current position based on the connection is detected, and the first threshold is set when the detection unit detects that the autonomous navigation unit is connected. Threshold changing means for reading from the storage unit and outputting to the GPS receiving unit, and when detecting that the autonomous navigation unit is not connected, reading the second threshold from the storage unit and outputting to the GPS receiving unit A portable navigation device comprising: 3. The portable navigation device according to claim 2, wherein the first threshold is a threshold giving priority to position accuracy. The portable navigation device according to claim 2, wherein the second threshold is a threshold giving priority to a positioning rate. 5. The portable navigation device according to claim 1, wherein the threshold is provided for at least one of an S / N value, a DOP value, an elevation value, and whether or not two-dimensional positioning is possible.

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