JP2006311002A - On-vehicle receiver and method of estimating reception difficulty region - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To comparatively easily estimate a reception difficulty region of terrestrial digital broadcast even if information about the reception difficulty region is not received from the broadcasting. <P>SOLUTION: A position information database 14a stores information in which each regional identification information, channels (remote control key ID) and the position information of a transmission station are correlated. A system controller 13 can recognize the position (latitude and longitude) of a transmission station based on the regional identification information acquired from the broadcast and the position information database 14a. The system controller 13 determines whether or not an altitude point exceeding the altitude (Z) of a plurality of lines connecting a plurality of positions of a topographical database 14b and the position of the transmission station acquired by the processing exists on the lines. Then, the system controller 13 estimates that a position on the topographical database 14b which is one end side of the lines determined that the altitude position exists is a reception difficulty region. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vehicle-mounted receiving device mounted on a vehicle and a method for estimating a difficult-to-receive location.

  A digital broadcast receiving apparatus that receives a digital broadcast using a terrestrial wave selects an arbitrary broadcast wave from a plurality of broadcast waves received through a terrestrial antenna by a digital tuner, and a plurality of broadcast waves included in the selected broadcast wave. An arbitrary channel is selected from among the channels by demultiplex processing, a digital signal of the selected channel is taken out, and a video signal and an audio signal are output by decoding the digital signal.

By the way, several techniques are disclosed regarding the in-vehicle digital broadcast receiving apparatus (see Patent Document 1 and Patent Document 2). Further, a configuration is disclosed in which both the broadcasting station and the receiver are provided with a difficult-to-receive area description table, and the receiver can store information on the difficult-to-receive area extracted from the broadcast wave in its own difficult-to-receive area description table ( (See Patent Document 3).
JP 2002-369099 A JP 2002-369245 A JP 2003-78429 A

  However, in actual broadcasting, the operation of transmitting the difficult-to-receive information described above is not performed.

  In view of the above circumstances, the present invention makes it possible to estimate a difficult reception place relatively easily without acquiring information on the difficult reception place from broadcasting. Furthermore, it aims at providing various information to a user based on this estimation result.

  In order to solve the above-described problems, an in-vehicle receiver according to the present invention is an in-vehicle receiver having a digital tuner that acquires various data from terrestrial digital broadcasting, a GPS function, and a display. A terrain database that indicates or indicates the height of the structure located there in addition to the elevation, a transmission station location database that indicates the latitude and longitude of the transmission station for each region, and a region identification of the broadcast from the received broadcast Means for acquiring the location of the transmitting station in the determined region and acquiring the position of the transmitting station in the determined region from the transmitting station location database, a plurality of locations of the acquired transmitting station and the topographic database Means for determining whether or not an altitude location exceeding the altitude of each line exists on each line connecting the position, and before the altitude location is determined to exist Means for estimating a position on the terrain database, which is one end side of the line and the receiver is difficult areas, characterized by comprising a.

  With the above configuration, it is possible to estimate the difficult reception area relatively easily without acquiring information on the difficult reception area from the broadcast.

  In the above configuration, the plurality of positions on the terrain database may be points obtained by dividing an area on the terrain database at a predetermined interval. In these configurations, it is preferable that the transmitting station location database holds information on the latitude and longitude of the transmitting station for each channel in each region. In these configurations, it is preferable to provide a difficult-to-receive location database in which information on a position estimated to be a difficult-to-receive location is stored. In the configuration including the difficult-to-receive location database, when the broadcast can be received at the position estimated to be the difficult-to-receive location, the location at which the reception was possible is deleted from the difficult-to-receive location database. It is good to be configured.

  In these configurations, based on the relationship between the travel position and the distance between the position estimated to be difficult to receive and the current position obtained by the GPS function, whether or not it will soon enter the difficult reception area It is good to be comprised so that it may judge. In such a configuration, when it is determined that the vehicle is about to enter the difficult reception area soon, a buzzer sound or a voice message for notifying that the mobile station is about to enter the reception difficult area may be output. In addition, when it is determined that the vehicle is about to enter a difficult-to-receive area soon, a text message for notifying that it will soon enter the difficult-to-receive area may be displayed on the display. Further, a memory for storing an image may be provided, and the image may be displayed on the display when it is determined that the vehicle is about to enter a place where reception is difficult. In addition, when it is determined that the vehicle will soon enter a difficult-to-receive area, the received sound of the digital broadcast may be gradually reduced. Further, when it is determined that data broadcasting data is being received, it is preferable to temporarily stop the data broadcasting data acquisition process when it is determined that the vehicle will soon enter a difficult-to-receive area.

  The vehicle-mounted receiving device having these configurations may include a car navigation function that has road map data and performs car navigation based on the GPS function. In such a configuration, the plurality of positions on the terrain database may be positions on a road on the road map data. In addition, in these configurations, based on the relationship between the travel direction and the distance between the position estimated to be a difficult reception location on the road map data and the current position on the road on the road map data, It may be determined whether or not the vehicle will enter an area where reception is difficult. In these configurations, the road on the route selected by the route calculation may be displayed in a specific color, while the color of the road on the ground that is difficult to receive may be displayed in a color different from the specific color. In these configurations, when there is a difficult reception place on the route selected by the route calculation, the reroute calculation may be performed so as to bypass the difficult reception place.

  In addition, the method of estimating a difficult-to-receive area according to the present invention includes latitude, longitude, and altitude, or topographic data indicating the height of a structure located there in addition to the altitude and the latitude of the transmitting station of digital terrestrial broadcasting. Is a method for estimating a difficult-to-receive area based on transmission station position data indicating longitude and longitude, and there are elevation points exceeding the elevation of each line on each line connecting the position of the transmission station and a plurality of positions on the terrain data. It is judged whether it exists, and it is estimated that the position on the topographic data which is the one end side of the line judged that the altitude location exists is a difficult reception place.

  In the above method, it is preferable to estimate a difficult reception area for each channel in each region based on the latitude and longitude information of the transmitting station for each channel in each region.

  As described above, according to the present invention, a difficult-to-receive area can be estimated relatively easily. By performing various processes before entering an area where it is difficult to receive terrestrial digital broadcasting, it is possible to avoid the user from feeling uncomfortable.

  Hereinafter, a vehicle-mounted receiving apparatus according to an embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the in-vehicle receiving apparatus includes a digital tuner unit 30 and a car navigation system (with built-in GPS) 40, and the video and audio received by the digital tuner unit 30 are received via the car navigation system 40. 40 LCD monitors 41 and speakers 42 are supplied. The system controller 13 of the digital tuner unit 30 transmits and receives information (position information, control information, etc.) to and from the control unit 40a of the car navigation system 40. Of course, a video display monitor and a map display monitor may be provided separately. Or you may employ | adopt the structure which displays an image | video and a map on one monitor by screen division. In some cases, a digital tuner unit with a monitor is provided on the rear seat, and a car navigation system with a monitor is provided on the driver's seat side. In such a case, the digital tuner unit and the car navigation system are provided by an in-vehicle LAN or the like. May transmit and receive information. Moreover, you may employ | adopt the structure which integrated the digital tuner unit and the car navigation system (refer Unexamined-Japanese-Patent No. 2003-324361).

  The in-vehicle antenna 1 receives the terrestrial digital broadcast and gives the received signal to the terrestrial digital tuner 2.

  The terrestrial digital tuner 2 extracts a signal of a specific frequency from the high frequency digital modulation signal including the video / audio data. The terrestrial digital tuner 2 includes a demodulation circuit, a deinterleave circuit, an error correction circuit, etc., and demodulates the selected digital modulation signal to output a transport stream.

  The demultiplexer (DEMUX) 3 converts the transport stream into MPEG2 (Moving Picture Experts Group 2) video stream, audio stream, PSI / SI (Program Specific Information / Service Information) and broadcast information (region identifier, service type). , Broadcast station identification, service number, etc.). The demultiplexer 3 supplies the video stream and the audio stream to the AV decoder 4 and supplies PSI / SI, broadcast information, and the like to the system controller 13.

  The AV decoder 4 includes a video decoder that decodes a video stream and an audio decoder that decodes an audio stream. The video decoder decodes the input variable length code to obtain a quantization coefficient and a motion vector, and performs inverse DCT conversion, motion compensation control based on the motion vector, and the like. The audio decoder decodes the input encoded signal to generate audio data. The video data generated by the decoding is output to the video processing circuit 5, and the audio data is output to the audio processing circuit 6.

  The video processing circuit 5 receives video data from the AV decoder 4 and performs D / A conversion, for example, to convert it into a composite video signal. The audio processing circuit 6 receives the audio data output from the AV decoder 4 and performs D / A conversion to generate, for example, a right (R) sound analog signal and a left (L) sound analog signal.

  The video processing circuit 7 and the audio output circuit 8 include an output resistor, an amplifier, and the like. The outputs of the video processing circuit 7 and the audio output circuit 8 are supplied to the LCD monitor 41 and the speaker 42 of the system 40 via the car navigation system 40.

  The OSD (On Screen Display) circuit 12 outputs video data based on character information and color information instructed to be output from the system controller 13 to the adder 20. The adder 20 performs processing for incorporating the video data into the received video data output from the AV decoder 4. The OSD circuit 12 can display a menu screen and various setting screens.

  The remote control transmitter 10 has various keys and sends various commands to the digital tuner unit 30. When the key is operated, a signal light (remote control signal) indicating a command corresponding to the key is emitted. Sent from the department. The remote control light receiver 11 receives the signal light, converts it into an electric signal, and gives it to the system controller 13.

  The boot ROM in the memory 14 stores a boot program. When the power is turned on, the system controller 13 executes from a boot program written in the boot ROM, and performs initialization necessary for the system. Various programs are expanded in a work memory (RAM) in the memory 14, and the system controller 13 executes the programs expanded in the RAM.

  The flash ROM in the memory 14 stores a digital broadcast ground station location information database 14a, a terrain (altitude) database 14b, and a difficult-to-receive location database 14c. The topography (elevation) database 14b stores, for example, a “numerical map 50 m mesh (elevation)” issued by the Geographical Survey Institute. This “numerical map 50 m mesh (elevation)” is a digital elevation model (DEM) obtained by calculation based on contour lines of a 1 / 5,000 topographic map. The altitude value of the center point of a grid (about 2 mm square on the map) obtained by dividing a two-dimensional mesh (a section of 15,000 topographic maps) into 200 equal parts in the latitude and longitude directions is recorded. The interval between elevation points is 1.5 seconds in the north-south direction, 2.25 seconds in the east-west direction, and the actual distance is about 50 m.

  The system controller 13 performs overall control in the digital tuner unit 30. In addition to this control, the system controller 13 performs channel scan processing, information acquisition processing such as a remote control key ID, channel selection button allocation processing, and the like. In particular, as processing according to the present invention, prediction processing of a difficult-to-receive area (a region or a spot where reception is difficult) is performed.

(Channel scan processing)
For example, when the digital tuner unit 30 is turned on for the first time every day (for example, when the first engine is started every day), when a broadcast that has been received can no longer be received, or when a channel scan command is received from the user, When it is determined by the navigation system that the area has changed, or every predetermined time, the system controller 13 performs a channel scan. The system controller 13 selects the lowest frequency in the UHF band at which the terrestrial digital broadcast is transmitted to the tuner 2 and performs stationed determination. When it is determined that the station is stationed (with digital broadcasting), the frequency information and the attached information (service identification, program information, etc.) separated from the received transport stream are extracted and stored in the memory. This process is continued until the highest frequency is increased (for example, up to 62 ch). The service identification in the attached information is, for example, a 6-bit area identification (area code), a 3-bit service type, a 4-bit regional carrier identification, and a 3-bit service number. The PSI is separated from the transport stream and extracted from the network information table (NIT). Can do.

(Remote control key key ID acquisition process)
In the channel search described above, the PSI is separated from the transport stream at the stationed frequency, and the remote control key ID is extracted from the NIT (Network Information Table).

(Channel selection button assignment process)
The channel selection button assignment process can be automatically executed based on the remote control key ID. In other words, when the broadcasting station adds “4” as a remote control key ID to the transport stream and transmits it, the digital tuner unit 30 receives the transport stream, acquires the remote control key ID, and selects it. A OO broadcast station is set to the station button "4" (frequency information and transport stream ID for receiving the XX broadcast station are associated with the channel selection button "4"). Thereafter, when the channel selection button “4” is operated by the user, the broadcast of the XX broadcast station is selected. The channel selection button assignment process can also be performed by individually assigning a broadcast station or the like to each channel selection button by a user operation.

(Area identification code))
As described above, in the flash ROM of the memory 14, as shown in FIG. 2, a location information database in which each area identification information, a channel (for example, a remote control key ID) and location information of the transmitting station are associated with each other. 14a is stored. For example, if there is information associated as “region identification = 40 (Osaka)”, “remote control key ID (channel) = 2”, “latitude (X) = A1, longitude (Y) = B1”, Osaka Thus, the system controller 13 can recognize that the transmitting station transmitting the terrestrial digital broadcast of 2 channels exists at the position indicated by (X = A1, Y = B1).

(Estimation processing for difficult-to-receive areas)
The system controller 13 has an altitude location exceeding the altitude (Z) of each line on each line connecting a plurality of positions in the terrain database 14b and the position (X = A1, Y = B1) of the transmitting station determined by the above processing. Determine whether or not. Then, it is estimated that the position on the terrain database 14b, which is one end side of the line where it is determined that the altitude location exists, is a difficult reception area. Specifically, the three-dimensional position of each place is specified by the altitude information, latitude, and longitude of each place on the topographic database 14b. Further, the three-dimensional position of the transmitting station is specified by the altitude information, latitude, and longitude of the transmitting station. The system controller 13 determines whether or not a point having a height exceeding the altitude Z of the line exists on the line connecting these two three-dimensional positions. Here, for example, in FIG. 2, it is assumed that a point A on the road D is a determination target site, a transmitting station exists at the B position, and a high mountain exists at the C position. In such a case, the system controller 13 determines that a point having a height exceeding the altitude Z of the line exists on the line. The system controller 13 performs such estimation processing for each point on the terrain database 14b (for example, at an actual distance of 5 meters). In the case where only the GPS function is provided, the estimation process is performed at each point on the terrain database 14b. In this embodiment, the car navigation system 40 is provided, and the car navigation system 40 is a road map. Since the data is provided, the estimation process can be performed only for the points on the road map data.

(Processing when it is difficult to receive)
When the system controller 13 estimates the difficult reception area as described above, the following processing is executed.

(1) The location information (latitude, longitude) estimated to be difficult to receive is stored in the difficult-to-receive location database 14c in association with the channel (number). The position (latitude and longitude) estimated to be difficult to receive differs depending on the channel (that is, the position of the transmitting station).

(2) Using the current position information of the vehicle and the difficult-to-receive location database 14c, if it is assumed that reception of the current channel is continued, it is determined whether or not the vehicle is about to enter the difficult-to-receive location soon. For example, when the distance between the position estimated to be difficult to receive and the current position is 50 m, for example, and the traveling direction is directed to the position estimated to be difficult to receive, the vehicle will soon enter a place where reception is difficult. Judge that it will be. Of course, the above determination may be made in consideration of the traveling speed. More specifically, the system controller 13 can acquire future vehicle position information from the navigation system 40. For example, if the destination is set and the route calculation is performed, the position information (planned position) of the future vehicle can be obtained by this route calculation. Even when the route calculation is not performed, it is possible to predict future vehicle position information to some extent (for example, until the vehicle turns right or left) from the relationship between the traveling direction of the vehicle and the road map data. it can. That is, the distance between the current position on the road and the estimated reception difficulty position on the road based on the road map data can be obtained. The traveling direction can be determined based on the output of the electronic compass or the difference between the position (latitude and longitude) at the time point t1 and the position (latitude and longitude) at the time point t2, but this method takes into account the bending of the road. I can't do it. Therefore, it is desirable to determine the traveling direction based on the road map data.

  As described above, the system controller 13 executes one or more of the following processes when it is determined that it will soon enter a difficult-to-receive area.

(1) A warning sound is emitted using a buzzer or speaker 42 (not shown). Alternatively, a voice message such as “There is a possibility that a broadcast cannot be received soon” is generated using a voice synthesis IC, a recording voice IC, or the like. In addition to this, or alternatively, the OSD function may be used to display on the LCD monitor 41 a text message such as “There is a possibility that the broadcast cannot be received soon”.

(2) Fade out the volume of the received voice. Further, another video stored in the memory is displayed on the LCD monitor 41 instead of the currently received video. As another video, an image stored in advance in the memory 14 (an image acquired from a removable recording medium, an image acquired from a network when it has a network connection function, or a chapter in broadcast reception) Examples include still images.

(3) For example, if the radio wave is interrupted while data broadcasting data is being received, the data (acquired data) that has been received so far may be canceled and return to the initial state. Therefore, when it is determined that the vehicle will soon enter a difficult-to-receive area, it is preferable to temporarily stop the data broadcast data acquisition or data broadcast display process to avoid the cancellation.

  The processes (modes) (1) to (3) are canceled when the vehicle exits from a land that is estimated to be difficult to receive. In the case of receiving the data broadcast, subsequent data acquisition is performed after the cancellation.

  The system controller 13 can provide the navigation system 40 with the difficult-to-receive area information stored in the difficult-to-receive area database 14c. An example of the processing contents of the navigation system 40 that has received the difficult-to-receive location information will be described below.

(1) The navigation system 40 has a function of displaying a road on a route selected by route calculation in a specific color (for example, yellow). Using the color display function and the difficult-to-receive information, the color of the road on the difficult-to-receive ground is displayed in a color (for example, red) different from the specific color.

(2) The navigation system 40 may perform re-route calculation so as to bypass the location when a certain location of the initial route selected by the route calculation exists in a difficult-to-receive area. In this re-route calculation, the route calculation may be performed on the assumption that there is no road (or no traffic) at the relevant location. The detour route selected by the reroute calculation may be displayed in, for example, the yellow color, and the red display on the ground that is difficult to receive in (1) may be left as it is. Such re-route calculation may be performed only when “YES” is selected in the selection menu such as “YES NO which gives priority to broadcast reception”.

  If the system controller 13 can actually receive digital broadcasting in the area determined to be a difficult reception area, the system controller 13 deletes the position information (latitude and longitude) of the received location from the difficult reception area database 14c. May be.

  In the above example, the terrain information database 14b stores "numerical map 50m mesh (elevation)", but is not limited thereto. Moreover, it is good also as having the data (for example, height information, such as a high-rise building, an elevated road, a steel tower, and its location information) other than topography data. If the altitude at the location (latitude, longitude) of the structure is acquired from the topographic information database 14b and the height of the structure is added to the altitude, the total altitude (Z) can be acquired.

  By the way, when the car navigation system 40 is not provided but only the GPS (global positioning system) function is provided, a plurality of positions on the terrain database 14b selected for determining the difficult-to-receive area are the terrain database 14b. Each point obtained by dividing the upper area at a predetermined interval. That is, it is not possible to select only the position on the road. Therefore, the difficult-to-receive area obtained in such a case is obtained regardless of the presence of the road, as shown in FIG.

  On the other hand, in the case where the car navigation system 40 is provided (when the road map data is provided in addition to the GPS function), as shown in FIG. It is also possible to select a position on the road as a plurality of positions. Alternatively, as shown in FIG. 4A, it is possible to estimate the difficult reception area on the road by estimating the difficult reception area and comparing the difficult reception area with the road map data.

  In any case, if the configuration is such that the estimation result of the difficult-to-receive area is stored in the database, the difficult-to-receive area estimation process needs to be performed only once. There is no need to estimate the difficult reception area in real time. When the difficult-to-receive area is estimated, vehicle position information is not necessary. For example, the position information of the vehicle is required in determining whether or not the broadcast can be received soon, using the estimation result of the difficult reception area.

It is the block diagram which showed the estimation method of the difficult reception area of embodiment of this invention. It is explanatory drawing which showed the transmission station location information database. It is explanatory drawing which showed the outline | summary of estimation of a difficult reception place. FIG. 4A is an explanatory diagram showing an outline of estimation of difficult-to-receive areas for the entire area, and FIG. 4B is an explanatory diagram showing an outline of estimation of difficult-to-receive areas on a road in the area. is there.

Explanation of symbols

1 Antenna 2 Tuner 3 Demultiplexer (DEMUX)
4 AV decoder 12 OSD circuit 13 System controller 14 Memory

Claims (18)

In an in-vehicle receiver equipped with a digital tuner that acquires various data from terrestrial digital broadcasting, a GPS function, and a display, the latitude, longitude, and altitude are indicated, or in addition to the altitude, the height of the structure located there The terrain database also shows, the transmission station location database showing the latitude and longitude of the transmission station for each region, and the region identification of the broadcast is obtained from the received broadcast to determine which region the broadcast is and Means for acquiring the position of the transmitting station in the area from the transmitting station position database, and on each line connecting the acquired position of the transmitting station and a plurality of positions on the terrain database, there is an altitude location exceeding the altitude of each line. And a position on the terrain database which is one end side of the line where the elevation point is determined to exist is difficult to receive. Vehicle type receiving apparatus characterized by comprising means for estimating that the earth, the. 2. The in-vehicle receiving device according to claim 1, wherein the plurality of positions on the topographic database are points obtained by dividing an area on the topographic database at predetermined intervals. apparatus. The in-vehicle receiving apparatus according to claim 1 or 2, wherein the transmitting station position database stores information on latitude and longitude of a transmitting station for each channel in each region. apparatus. 4. The on-vehicle receiver according to claim 1, further comprising a difficult-to-receive location database in which information on a position estimated to be a difficult-to-receive location is stored. . 5. The in-vehicle receiving device according to claim 4, wherein when a broadcast can be received at a position estimated to be a difficult-to-receive location, the location at which the reception was possible is deleted from the difficult-to-receive location database. An in-vehicle type receiving apparatus configured as described above. The in-vehicle receiver according to any one of claims 1 to 5, wherein a distance between a position estimated to be a difficult reception place and a current position obtained by the GPS function is related to a traveling direction. A vehicle-mounted receiving apparatus configured to determine whether or not to enter a difficult-to-receive area soon. The in-vehicle type receiving device according to claim 6, wherein when it is determined that the vehicle is about to enter a difficult reception area, a buzzer sound or a voice message for notifying that it is about to enter the difficult reception area is output. A vehicle-mounted receiving device. 8. The vehicle-mounted receiving device according to claim 6 or 7, wherein when it is determined that the vehicle is about to enter a difficult reception area, a character message for notifying that it is about to enter the difficult reception area is displayed on the display. An in-vehicle receiver characterized by the above. 9. The in-vehicle receiving device according to claim 6, further comprising a memory for storing an image, and displaying the image on the display when it is determined that the vehicle is about to enter a place where reception is difficult. An in-vehicle receiver characterized by the above. The in-vehicle receiver according to any one of claims 6 to 9, wherein when it is determined that the vehicle is about to enter a place where reception is difficult, the received sound of the digital broadcast is gradually reduced. A vehicle-mounted receiving device. 11. The vehicle-mounted receiving device according to claim 6, wherein when data broadcast data is received, when it is determined that the vehicle is about to enter a place where it is difficult to receive, the data broadcast data acquisition process is temporarily performed. The in-vehicle type receiving apparatus characterized by stopping automatically. 12. The in-vehicle receiving apparatus according to claim 1, further comprising a car navigation function that has road map data and performs car navigation based on the GPS function. 13. The in-vehicle receiver according to claim 12, wherein the plurality of positions on the topographic database are positions on a road on the road map data. The in-vehicle receiving device according to claim 12 or 13, wherein a distance between a position estimated to be a difficult reception place on the road map data and a current position on the road on the road map data; A vehicle-mounted receiving apparatus configured to determine whether or not to enter a difficult-to-receive area soon based on a relationship with a traveling direction. 15. The in-vehicle receiving device according to claim 12, wherein a road on a route selected by route calculation is displayed in a specific color, and a color of the road on the ground that is difficult to receive is displayed in the specific color. A vehicle-mounted receiving device characterized by displaying in a different color. The in-vehicle receiver according to any one of claims 12 to 15, wherein when there is a difficult reception place on a route selected by the route calculation, a reroute calculation is performed so as to bypass the difficult reception place. A vehicle-mounted receiving device characterized by being configured to perform. Receiving is difficult due to terrain data indicating latitude, longitude and altitude, or in addition to the above altitude, the height of the structure located there, and transmitting station position data indicating the latitude and longitude of the transmitting station of digital terrestrial broadcasting A method for estimating the ground, wherein it is determined whether or not an altitude location exceeding the altitude of each line exists on each line connecting the position of the transmitting station and a plurality of positions on the topographic data, and the altitude location exists Then, it is estimated that the position on the terrain data that is one end side of the line determined to be a difficult-to-receive place, and is a difficult-to-receive place estimation method. 18. The difficult-to-receive area estimation method according to claim 17, wherein the difficult-to-receive area for each channel in each area is estimated based on the information on the latitude and longitude of the transmitting station for each channel in each area. How to estimate the difficult reception area.

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