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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a map displaying apparatus, and particularly to a map displaying apparatus which can display a map on a screen with facilities superimposed on the map.
2. Description of the Related Art
A car navigation system is installed in a car and detects the position of the car as the car travels by means of GPS or the like and displays that position on a display together with a road map to help the driver of the car reach a destination
smoothly. Navigation systems which not only show the present position of the car but also display marks representing certain facilities such as, for example, gas stations and restaurants are also known, and these are effective when a driver wants to go
to one of these facilities. Specifically, when a driver selects a category of facility to be displayed, for each facility of that category located in the region covered by the map on which the present position of the car is being displayed, the
navigation system displays a facility mark M denoting that facility in the appropriate position on the map.
In the display example shown in FIG. 4A, there are only a few facility marks M. Therefore, it is possible to distinguish easily with roads as references the positions in which the facilities are located. However, such facilities are not
distributed evenly in all areas, and the density in which facilities exist is different in different areas; for example, facilities of the same category may exist in concentration in urban areas while being only found here and there in country areas.
Consequently, for example in the display example shown in FIG. 4B, although the scale of the map is the same as that of FIG. 4A, because there is a high concentration of facilities of the selected category, there are many facility marks in the map region
being displayed and the roads themselves are hidden. When the roads are hidden, it is impossible for the route to a chosen facility to be distinguished, and the benefit of the facility guidance is lost. When, on the other hand, facilities of the
selected category are few and far between, it may happen that no facility mark is displayed in the map region being displayed. In this case also the benefit of the facility guidance is lost.
Therefore, when as in the display example shown in FIG. 4B there are too many facility marks, it is necessary for the scale of the displayed map to be increased to obtain a suitable density of facility marks, for example as shown in FIG. 4C.
(The scale of the displayed map shown in FIG. 4C is four times the scale of the displayed map shown in FIG. 4B.) When, on the other hand, no facility marks whatsoever are displayed in the map region being displayed, reversely it is necessary for the
scale of the displayed map to be reduced until there is at least one facility mark in the map region being displayed. The user himself or herself has had to understand these facility mark display states and perform an operation to change the scale to
one which the user finds easy to read, and this has been extremely troublesome.
Also, in a navigation system, when a user is specifying a facility, there are times when although the user knows the category of the facility (for example Airport, Bank, Gas Station or Park) and perhaps even the individual name of the facility
(for example XX Airport, XY Branch of XZ Bank, YX Gas Station or YY Park or the like), because the user is unfamiliar with the geography of the vicinity in which the facility is located, he or she is unable to locate the position of the facility on a
map. To make it possible for a user to specify a facility even in this kind of case, data search systems capable of searching for data indicating the position of a facility on the map from the category and/or the individual name of the facility are in
use.
However, when a user specifies the category of a facility, the data search system finds all facilities of that category that have been preregistered in the system. Here, when many facilities of the same category have been preregistered, if all
the facilities found are displayed randomly on the display, the user looking at that display may be at a loss to decide which facility to choose.
To avoid this, some data search systems in the related art have a function of, when many facilities of the same category have been preregistered, rearranging the many facilities found in the order of their proximity to the present position and
displaying these rearranged facilities on the display in the form of a list. With this function, because facilities close to the present position can be ascertained just by looking at the display, it is easy for the user to choose a facility. The
processing of rearranging the facilities found in a search in the order of their proximity to the present position is carried out by a microcomputer.
However, when many facilities found in a search are being rearranged in the order of their proximity to a present position, the more facilities there are the longer the processing time required for their rearrangement becomes. When an ordinary
sorting algorithm is used, the processing time required for the rearrangement increases exponentially with respect to the number of facilities (the amount of data) found in the search.
As the waiting time from when a user specifies a category of facility to when facilities of that category found in a search are displayed on a display, normally, although there are differences among individuals, the limit that a user will
tolerate is said to be about two to three seconds. However, when many facilities are found in the search, it takes a great deal of time from the user specifying the facility category to the facilities of that category found in the search being displayed
on the display, and there is a risk of this time exceeding the limit that the user will tolerate.
SUMMARY OF THE INVENTION
It is therefore a first object of the invention to provide a map displaying apparatus capable of automatically changing the scale of a displayed map to a scale such that it is easy for a user to see facilities displayed on the map. Also, it is a
second object of the invention to provide a searching system capable of carrying out a search of facilities relatively quickly even when there are many facilities matching the search criteria.
To achieve the above-mentioned first object and other objects, the invention provides a map displaying apparatus comprising a displaying device for displaying a map, a map storing device for storing multiple maps showing predetermined areas with
different scales, a facility storing device for storing facilities located in respective positions on the maps, a facility category selecting device for selecting a category of facility to be displayed on the displaying device, and a display controlling
device for displaying one of the maps having different scales stored in the map storing device on the displaying device and displaying facilities selected using the facility category selecting device in their respective positions on the displayed map.
The map displaying apparatus also comprises a map scale controlling device for changing the scale of the map displayed on the displaying device, as necessary, so by the display controlling device that the number of facilities displayed on the map by the
display controlling device is kept below a predetermined upper limit.
In this map displaying apparatus, multiple maps showing predetermined areas with different scales are stored in the map storing device, and the display controlling device displays one of the maps having different scales stored in the map storing
device on the displaying device. When a category of facility is selected using the facility category selecting device, facilities of that selected facility category which are located in the area covered by the map displayed on the displaying device are
displayed in their respective positions on that map. The map scale controlling device as necessary so changes the scale of the map displayed on the displaying device by the display controlling device that the number of facilities displayed on the map by
the display controlling device is kept below the predetermined upper limit.
Thus, even in cases where for example as in the display example shown in FIG. 4B, map display is being carried out on a scale such that, because facilities exist in concentration, there are many facility marks within the map region being
displayed and the roads themselves are hidden by the facility marks and consequently it is impossible to distinguish the route to a chosen facility, the map displaying apparatus described above can automatically increase the map scale so that the number
of facilities being displayed on the map is kept below the predetermined upper limit (see FIG. 4C). Because the apparatus itself carries out the scale change automatically in this way, without the user himself or herself having to understand these
facility mark display states and change the scale of the map being displayed to a scale such that the display is easy to read, it is extremely convenient.
The processing of changing the scale of the displayed map so that the number of facilities displayed on the map by the display controlling device is kept below the predetermined upper limit can be realized for example in the following way.
First, the map scale controlling device changes the scale of the displayed map to a largest available scale and then it reduces the scale of the map one level at a time until the number of facilities displayed on the map is equal to or above a
lower limit. Then, when the number of facilities is equal to or above the lower limit, the map scale controlling device determines whether or not the number of facilities is equal to or below an upper limit when the scale of the map is reduced further
by one level. And then only when the number of facilities in this case is equal to or below the upper limit, it further reduces the scale of the map by one level.
Or, alternatively, the map scale controlling device first determines whether or not the number of facilities displayed is within a predetermined range defined by a predetermined lower limit and a predetermined upper limit. When the number of
facilities is below the lower limit, it reduces the scale of the map one level at a time until the number of facilities displayed on the map is equal to or above the lower limit. When the number of facilities is equal to or above the lower limit, it
determines whether or not the number of facilities is equal to or below the upper limit when the scale of the map is further reduced by one level. Only when the number of facilities in this case is equal to or below the upper limit, it further reduces
the scale of the map by one level. When on the other hand the number of facilities initially exceeds the upper limit, it increases the scale of the map until the number of facilities displayed on the map is equal to or below the upper limit. Of course,
the scale of the displayed map can be so changed that the number of facilities displayed is kept equal to or below a predetermined upper limit by a method other than those described above.
There may also be cases wherein not a single facility is displayed on the displayed map even when the scale of the map is reduced to a smallest available scale. In this case, it is preferably displayed on the displaying device that no facility
can be displayed.
As the above-mentioned predetermined range, for example the lower limit is made 1 and the upper limit is made 50. The upper limit and lower limit values of the predetermined range are of course not limited to these examples, but a certain amount
of allowance is necessary in the range of values. That is, if a narrow range of for example from a lower limit of 10 to an upper limit of 20 is set there will be more cases wherein no map of corresponding scale exists, and such a narrow range is
therefore unrealistic.
Also, there may be situations wherein after control automatically keeping the number of facilities within a predetermined range has been carried out a user wants to further increase the scale by one level or reduce the scale by one level. For
example when facilities are concentrated locally it may be beneficial to further increase the scale of the map to help distinguish between them. Accordingly, scale selecting device for selecting a scale of map to be displayed on the displaying device
may be provided so that, after the map scale controlling device has so changed the scale of the map that the number of facilities displayed is kept to within a predetermined range, a scale of map can be selected using the scale selecting device. In this
case, the map scale controlling device can find a map of this selected scale from the map storing device and change the map displayed on the displaying device by the display controlling device to a map of the selected scale. When this is done, the user
can as necessary carry out fine control of the scale of the displayed map.
Also, present position detecting device for detecting the present position of the vehicle may be provided and the display controlling device constructed to display a map of the vicinity of the present position detected by the present position
detecting device with that present position at its center.
To achieve the above-mentioned second object, the invention provides a searching system which, when in a search for specified facilities in the vicinity of a given location on a map the number of facilities of a selected category exceeds a preset
upper limit, only searches facilities located in a predetermined region centering on the vicinity of the given location. By this means, the number of facilities searched can be kept below a preset upper limit. Therefore, even when there are a large
number of facilities of the selected category it is possible for a facility search to be carried out relatively quickly. Also, because the facility search is carried out with a range close to the given location being given priority, the information
produced by the search is more useful to the user.
In this searching system, when the number of facilities of the selected category is no greater than the preset upper limit, a searching device may search for all the facilities of the selected category. In this case, the search processing time
can be kept short even though all the facilities are being searched for.
Also, in the searching system described above, by the predetermined region being enlarged until the number of facilities of the selected category is equal to or above a preset lower limit, it is possible to search for a suitable number of
facilities equal to or above the preset lower limit in a range as close as possible to the given location.
By stopping the enlargement of the predetermined region when the number of facilities is below the preset lower limit even when the predetermined region has been enlarged to a maximum range, it is possible to prevent unnecessary prolongation of
the search time.
Also, when the number of facilities is below the preset lower limit even when the predetermined region has been enlarged to a first maximum range, because the number of facilities existing per unit area of the map is very small, even when the
predetermined region is enlarged the number of facilities will not increase quickly. Therefore, by greatly increasing the rate of enlargement of the predetermined region, that is, by enlarging the predetermined region toward a second maximum range at
the increased rate, it is possible to find a number of facilities equal to or above the preset lower limit in a range close to the given location swiftly.
In the searching system described above, it is possible to provide a category selecting device with which a category of facility can be selected and facilities of the selected category in the vicinity of a given location can then be searched for. Here, category of facility means for example Bank, Gas Station, or Park.
When a plurality of categories of facility are selected using the category selecting device, the searching system may search for facilities of all the categories selected by the category selecting device.
And not only a category of facility but also a distinction based on characteristics of facilities can be specified and facilities of the specified distinction then searched from among facilities of the specified category in the vicinity of a
given location. Here, distinction based on characteristics of facilities means for example the name of a bank when the category is Bank, the name of a petroleum company when the category is Gas Station, or the type of a restaurant (for example Japanese,
Chinese or French) when the category is Restaurant.
The searching system described above may also comprise a position detecting device for detecting the present position, and the searching device may search facilities using the present position detected by the position detecting device as the
given location.
In the searching system described above, an information search particularly useful to the user can be carried out by facilities found by the searching device being rearranged in the order of their proximity to the given location by a
rearrangement processing device and displayed in the form of a list.
In the searching system described above, by the above-mentioned preset upper limit being set in correspondence with a total time made up of the time required for the search processing carried out by the searching device and the time required for
the rearrangement processing carried out by the rearrangement processing device, the search processing time can be kept short. Therefore, by the above-mentioned total time being set to a maximum time that a user will tolerate (normally about two to
three seconds) it is possible to prevent the patience of the user from being unnecessarily strained.
The searching device in the searching system described above can be realized by means of a computer-readable recording medium recorded with a computer program.
That is, means for realizing the searching device in the searching system described above can be provided as a program to be executed by a computer system. This program is recorded on a computer-readable recording medium such as a semiconductor
memory, a hard disc, a floppy disc, a data card (for example an IC card or a magnetic card), an optical disc (CD-ROM, DVD or the like), an opto-magnetic disc (for example an MD), a phase change disc or magnetic tape, and is loaded into a computer system
as necessary for use. Alternatively, the program may be recorded on a ROM or a backup RAM as the computer-readable memory and this ROM or backup RAM then built into a computer system.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other objects, features and characteristics of the present invention will be appreciated from a study of the following detailed description, the appended claims, and drawings, all of which from a part of this application. In the
drawings:
FIG. 1 is a block diagram showing the overall construction of a map displaying apparatus for mounting in a vehicle according to a first preferred embodiment of the present invention;
FIG. 2 is a flow chart showing facility display processing executed in a control part of the first preferred embodiment;
FIG. 3 is a flow chart showing another version of the facility display processing;
FIGS. 4A through 4C are views showing facility display examples;
FIG. 5 is a block diagram showing the construction of a second preferred embodiment of the present invention;
FIGS. 6A and 6B are views illustrating display examples in the second preferred embodiment;
FIGS. 7A and 7B are views illustrating map data files and facility data files of the second preferred embodiment;
FIG. 8 is a flow chart illustrating processing carried out in the second preferred embodiment;
FIG. 9 is another flow chart illustrating processing carried out in the second preferred embodiment;
FIGS. 10A through 10D are schematic views illustrating processing carried out in the second preferred embodiment;
FIGS. 11A through 11C are further schematic views illustrating processing carried out in the second preferred embodiment; and
FIG. 12 is a characteristic chart illustrating an action of the second preferred embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
First Preferred Embodiment
As shown in FIG. 1, a map displaying apparatus 2 comprises a position detector 4, a map data inputter 6, control switches 8, an external memory 12, a display 14 and a remote control sensor 15, and a control part 10 connected to these. The
control part 10 consists of an ordinary computer, and inside it are a CPU, ROM, RAM, an I/O circuit, and bus lines connecting these together.
The position detector 4 has a gyroscope 18, a distance sensor 20, and a GPS (Global Positioning System) receiver 22 for detecting the position of the vehicle in which the map displaying apparatus 2 is installed on the basis of radio waves from
satellites, all three of these devices constituting known technology.
Because these devices 18, 20 and 22 all have errors of different kinds, in using them the position detector 4 is constructed to interpolate their outputs. Depending on the accuracy of the above-mentioned devices one or more of them may be
dispensed with, and also a steering rotation sensor, or wheel speed sensors of driven wheels or the like may be used as the position detector 4.
The map data inputter 6 is a device for inputting data including so-called map matching data for increasing the accuracy of the position detection, map data, and facility data to the control part 10, which will be further discussed later. As the
recording medium of the map data inputter 6, because the amount of data is large, a CD-ROM is normally used, but for example another medium such as a DVD or a memory card may alternatively be used.
The map data is data constituting maps by connecting together multiple nodes such as intersections with links, and with respect to each of the links is stored link information made up of a unique number specifying the link (the link ID), a link
length showing the length of the link, X and Y coordinates of a starting end and a finishing end of the link, and a road width and a road type of the link (indicating road information such as that the road is a toll road). The construction of this map
data using link information and so on is the same as in related art. However, in the case of this preferred embodiment, for displaying maps having different scales on the display 14, a plurality of maps expressing a predetermined geographical area on
four different scales such that the length of about one tenth of the width of the display screen is equivalent to A, B, C and D respectively are stored as map data. The relationships between the above-mentioned four lengths A, B, C, D are made D=4C,
C=4B, B=4A. Each of the maps can be displayed reduced in size by 1/2 (halved in scale), and thus map display on eight different scales such that the length of about one tenth of the width of the display screen is equivalent to A, 2A, B, 2B, C, 2C, D and
2D is possible. Using A as a reference length, the above-mentioned eight lengths can also be expressed as A, 2A, 4A, 8A, 16A, 32A, 64A and 128A.
The facility data is data for showing facilities that can be displayed on a displayed map. For each facility, for example, a facility category and a position of the facility when displayed on a map is stored as the facility data. Facility
categories include for example those denoting relatively large field areas which may also contain buildings, such as Airport, Golf Course or Park, those mainly denoting buildings themselves, such as Hotel, Hospital, City Office and Library, and those
mainly denoting small installations such as ATM (Automatic Teller Machine). Facilities likely to be relatively numerous are for example restaurants, ATMs, gas stations and hotels. Conversely, large-scale facilities such as airports and ports, and
special facilities such as law courts, are relatively few in number. However, even among categories of facility likely to be relatively numerous, there will be those which while being numerous in city areas are scarce in country areas and those of which
the reverse is the case.
The position detector 4, the map data inputter 6, the control switches 8, the control part 10, the display 14 and the remote control sensor 15 and so on constitute a so-called navigation system. A present vehicle position mark, which will be
further discussed later, responsive to the present position detected by the position detector 4; map data inputted by the map data inputter 6; and also additional data such as guide routes, names, and signs can be displayed together on the screen of the
display 14.
This map displaying apparatus 2 also has a route guidance function of, when the position of a destination, and necessary specifications of a particular route (that is, specifications of points to be passed through) such as expressways and the
like are inputted from a remote control terminal 15a through the remote control sensor 15 or the control switches 8, automatically selecting an optimal route from the present position to that destination and displaying a corresponding guide route on the
display 14. As methods for automatically setting an optimal route like this, the Dikstra method and the like are known. The control switches 8 are for example touch switches integral with the display 14 or mechanical switches, and are used to make
various inputs. This setting and displaying of a guide route is not a principle characterizing part of the present invention and therefore will not be explained in detail here.
Next, of processing executed by the control part 10, facility display processing will now be described with reference to the flow chart of FIG. 2.
First, processing for displaying a map to be displayed is carried out (S110). As the selection of this map to be displayed, for example a user himself or herself may specify a map of a geographical area that he or she wants to be displayed, or
alternatively the user may leave this selection to processing automatically displaying a map of the vicinity of the present position. When a present position vicinity map is automatically displayed, the present position of the vehicle is calculated from
a signal from the position detector 4 and a present position vicinity map is read from a CD-ROM set in the map data inputter 6 and displayed. When on the other hand the user wants to specify a map of an area that he or she wants to be displayed, he or
she may do so by specifying a place name or the like or by scrolling displayed maps.
Then, when a facility display switch among the control switches 8 is pressed (S120), a facility category selection window is displayed (S130). These facility categories, as mentioned above, are for example Airport, Golf Course, Park, Hotel,
Hospital, City Office, Library, Restaurant, ATM, Gas Station and so on.
When one of these facility categories is selected by the user (S140), in the following S150, the scale of the map displayed on the display 14 is automatically changed to the most detailed map scale available and facility marks M are displayed in
the positions of respective facilities on that map.
In S160, it is determined whether or not at least one facility is displayed on the map. When at least one facility is displayed on the map (S160: YES), processing proceeds to S170 and calculates the number of facilities (n) that would appear on
a map of a scale one level smaller (a map whose geographical coverage is one level greater). In the following S180, it is determined whether or not this number of facilities n is greater than 50. When the number of facilities n is greater than 50
(S180: YES), the present processing ends directly. But, when the number of facilities n is equal to or below 50 (S180: NO), the processing proceeds to S190 and the map being displayed is automatically changed to a map of a scale one level smaller (a map
whose geographical coverage is one level greater). Processing then returns to S170.
When in S160 a negative determination is made, that is, when not even one facility is displayed on the map, processing proceeds to S200. In S200, it is determined whether or not the display state of the map is at the smallest scale at which
facilities can be displayed. If it is at the smallest scale (S200: YES), a message display saying, No facilities can be displayed. is displayed on the display 14 (S210), and the present processing ends. When on the other hand the present scale is not
the smallest scale at which facilities can be displayed (S200: NO), the map displayed is automatically changed to a map one level smaller in scale (a map one level greater in geographical coverage) (S220), after which the processing returns to S160.
In this way, in the case of the processing shown in FIG. 2, when a category of facility to be displayed is selected (S140), first the map being displayed is changed to a map of the most detailed (largest) scale available (S150), and then the
scale of the map is reduced (its geographical coverage is increased) by one level at a time until the number of facilities displayed on the map is at least a lower limit of 1 (S16O, S200, S220). Then, when the number of facilities n has become at least
1 (S160: YES), it is determined whether or not the number of facilities that would appear on a map one level larger in geographical coverage is equal to or below an upper limit of 50 (S180). Only when that number of facilities n is equal to or below the
upper limit of 50 (S180: NO), the map is automatically changed to a map one level larger in geographical coverage (one level smaller in scale) (S190).
Therefore, even in cases such that, for example as in the display example shown in FIG. 4B, map display would be carried out at a scale such that because there is a high concentration of facilities of the selected category there are many facility
marks in the map region being displayed and the roads themselves are hidden and it is impossible for the route to a chosen facility to be distinguished, according to the map displaying apparatus 2, the map scale is automatically increased so that the
number of facilities n displayed on the map is kept equal to or below the upper limit of 50. As a result, map display is effected with a suitable scale like that illustrated in FIG. 4C. When on the other hand there are no facility marks whatsoever in
the map region being displayed, the scale of the map display is reversely reduced until at least one facility mark does appear. In this way, the extremely valuable convenience that the apparatus itself automatically performs scale changes, without the
user having to understand these facility mark display states and carry out an operation himself or herself to change the scale to one which is easy to read, is realized.
Also, when no facility is displayed on the map even when the scale of the displayed map has been changed to a smallest scale (greatest coverage) (S200: YES), a message to the effect that no facility that can be displayed exists is displayed on
the display 14 (S210). Thus the convenience that this situation is made clear to the user is realized.
In this preferred embodiment, the display 14 is displaying means, the position detector 4 is present position detecting means, the control switches 8 are facility category selecting means, and the map data inputter 6 and the CD-ROM set therein
are map storing means and facility storing means. Also, the processing of steps S150 through S200 of the flow chart of FIG. 2 constitutes map scale controlling means.
The aspect of the present invention illustrated by the first preferred embodiment described above is not limited to this preferred embodiment and can be practiced in various other embodiments.
For example, although, in the first preferred embodiment described above, first the scale of the displayed map is changed to a most detailed (largest) scale (S150) and then if necessary the map scale is changed (reduced) to increase the
geographical coverage of the map one level at a time, alternatively it may be determined whether or not the number of facilities displayed n is within a predetermined range and processing then carried out on the basis of the result of that determination. An example of processing for this case is shown in the flow chart of FIG. 3.
Because the processing of S510 through S540 of the flow chart of FIG. 3 is the same as the processing of S110 through S140 of the flow chart of FIG. 2 it will not be described again here and only the processing of S550 onward will be described.
Whereas in the case of the flow chart of FIG. 2 at this point the scale of the displayed map is changed to a most detailed (largest) scale, in S550 of FIG. 3, the scale of the map having been displayed in S510 is not changed and instead processing for
displaying facility marks M in their respective positions is simply carried out.
Then, the number of facilities (n) is calculated (S560), and it is determined whether or not the number of facilities n is in a predetermined range, for example 1.ltoreq.n.ltoreq.50 (S570). If 1.ltoreq.n.ltoreq.50 (S570: YES), because n is
already in the predetermined range, it is not necessary for the scale to be changed and therefore processing ends directly.
If on the other hand 1.ltoreq.n.ltoreq.50 is not satisfied (S570: NO), in the following S580 it is determined whether or not the number of facilities n is 0.
If n is not 0 (S580: NO), because this means that n>50, processing proceeds to S590 and automatically changes the scale of the map to a geographical coverage smaller (a scale larger) by one level. Processing then returns to S560 and
calculates the number of facilities n again and the processing of S570 and S580 above is repeated. That is, because in this case the number of facilities initially is too great, the scale of the map displayed is increased (the geographical coverage of
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