Automotive navigation system

An automotive navigation system wherein a memory included therein has not stored therein picture information of an actual map, but instead has stored therein geographical names and the geographical positions thereof. When the geographical names of a departure point, a destination point and one or more passing points are entered through an input unit, a control circuit reads out the respective positions of the points from the memory. The control circuit controls a display unit to display on a display screen marks respectively indicating two or more of the points and the current position of a vehicle.

BACKGROUND OF THE INVENTION 
This invention relates to an automotive navigation system, and in 
particular to an automotive navigation system wherein a departure point, a 
destination point, and the current point of a vehicle are displayed with 
respective marks on a display such as a cathode ray tube. 
Such an automotive navigation system has been already proposed in Japanese 
Patent Application Laid-open No. 58-146814. This conventional system 
detects the running distance and the heading of a vehicle and computes the 
current position of the vehicle from those information. This system also 
displays a map as picture information read out from a memory on the 
display such as a CRT while displaying the mark indicating the current 
position of the vehicle which is computed on the display, whereby a driver 
can determine the current position of the vehicle from the map and the 
mark imaged on the display. 
However, since an extremely numerous amount of information is required to 
display the picture information as a map, a storage means for storing such 
amount of information and therefore a navigation system per se must be 
correspondingly large-scaled and expensive. Accordingly, it is desirable 
to develop a small-sized and cheap navigation system suitable for boarding 
it on a vehicle. 
In a case where a departure point and a destination point are 
predetermined, even though a map stored in the memory is displayed on the 
display and a mark indicating the current position of the vehicle is 
displayed in a superposed manner, the map to be displayed on a reduced 
scale is in certain conditions so small that the current position of a 
vehicle can not be clearly displayed. Furthermore, if the distance between 
the departure point and the destination point is far so as to require a 
plurality of sequencial maps, it is very hard and cumbersome to grasp the 
entire running route. 
Although it is not necessarily impossible to solve these technical problems 
with a memory having a large capacity as well as a high speed arithmetic 
device, the size of the whole system becomes very large so that it is 
difficult to board the same on the vehicle. 
On the other hand, there have been disclosed, "Cathode-Ray Tube Information 
Center with Automotive Navigation" published in SAE Technical Paper Series 
840313 by M. W. Jarvis and R. C. Berry, and "On-Board Computer System for 
Navigation, Orientation, and Route Optimization" published in SAE 
Technical Paper Series 840485 by P. Haeussermann. Both publications are 
based on an international Congress & Exposition held in Detroit, Mich. on 
Feb. 27-Mar. 2, 1984. In the former literature, an approximate position of 
a vehicle is determined from the communication with a satellite, and a 
more accurate position is determined and displayed on the CRT by means of 
a self-contained navigation using an earth magnetism sensor in the 
vehicle. The latter literature discloses a composite system of a route 
guide system in trunk (main) highways using distance information and a 
destination indicating system within a city using distance information and 
heading information. 
SUMMARY OF THE INVENTION 
It is accordingly an object of the present invention to provide an 
automotive navigation system wherein a memory included therein has not 
stored therein picture information of an actual map, but instead has 
stored therein geographical names and the geographical positions thereof. 
When the geographical names of a departure point, a destination point and 
one or more passing points are entered through an input unit, a control 
circuit reads out the respective positions of the points from the memory. 
The control circuit controls a display unit to display on a display screen 
marks respectively indicating either two or more of the points and the 
current position of a vehicle on an adequately reduced scale. This 
arrangement of an automotive navigation system can perform a fully 
practical navigation function even with a small sized cheap memory and 
arithmetic unit. 
In order to accomplish this object, an automotive navigation system 
according to this invention, broadly, comprises a running distance 
detecting means for detecting the running distance of a vehicle; a vehicle 
heading detecting means for detecting the heading of the vehicle; a 
display means for enabling a planar display based on the two dimensional 
Cartesian coordinates system; storage means for storing information 
comprising a geographical name and the positional information thereof for 
each of a plurality of points; and a control means for designating the 
geographical names of a departure point, a destination point, and at least 
one passing point along the path of the vehicle, reading out the 
positional information from the storage means of the designated 
geographical names, and receiving signals from the running distance 
detecting means and the heading detecting means. This control means 
further including means for computing coordinates on the display means of 
marks indicative of two or more of the departure, destination, and passing 
points and the current position of the vehicle on the basis of their 
mutual positional relationship and in a reduced scale determined by said 
two or more points, respectively, and controlling the display means to 
display said marks at the computed coordinates. 
The control means preferably comprises a current position computing means 
for computing the current position of the vehicle from the running 
distance detected by the running distance detecting means and the vehicle 
heading detected by the vehicled detecting means; a current position 
initializing means for initializing the current position of the vehicle 
for the current position computing means; a point setting means for 
entering the geographical names of the departure point, the destination 
point, and the passing point or points of the vehicle, for retrieving the 
geographical names from the storage means, for reading out positional 
information corresponding to the geographical names, and for setting the 
positional information as the positions of the points; an all-points 
display control means for controlling the display means to display marks 
indicative of the respective positions of all of the points set by the 
point setting means and to display a mark indicative of the current 
position of the vehicle in a reduced scale determined by all of the 
points; a section setting means for selecting a section defined by less 
than of all of the points; a sectional display control means for 
controlling the display means to display marks indicative of the 
respective positions of selected points defining the selected section and 
to display a mark indicative of the current position of the vehicle in a 
reduced scale determined by the selected points; and a display changeover 
means for selectively connecting one of the all-points display control 
means and the section display control means to the display means. 
The all-points display control means preferably includes means for 
controlling the display means to display two of the marks indicative of 
two of all of the set points on the outer periphery of a rectangular zone 
as imaginarily provided on the screen of the display means. The sectional 
display control means preferably includes means for controlling the 
display means to display the marks indicative of two of the selected 
points on the outer periphery of a rectangular zone as imaginarily 
provided on the screen of the display means. 
The all-points display control means may further comprise means for 
computing coordinates on the display means of the departure, destination, 
and passing points and the current position of the vehicle on the basis of 
the mutual positional relationship therebetween, means for determining the 
maximum and minimum values of the positional information of all of the 
points entered, and means for determining the middle point between the 
maximum and minimum values, and means for converting the positional 
information to the coordinate system by rendering the middle point 
coincident with the central point of the screen. 
The sectional display control means may further comprise means for 
computing coordinates on the display means of the selected points and the 
current position of the vehicle on the basis of the mutual positional 
relationship therebetween, means for determining the maximum and minimum 
values of the positional information of the selected points, means for 
determining the middle point between the maximum and minimum values, and 
means for converting the positional information to the coordinate system 
by rendering the middle point coincident with the central point of the 
screen. 
The section setting means preferably comprises means for setting a desired 
section by sequentially retrieving the existing sections between the 
departure point and the destination point. The display changeover means 
preferably comprises means for entering an all-points selection and a 
section selection. 
The all-points display control means may further comprise means for 
additionally displaying a message representative of all-points or means 
for additionally displaying a message representative of the geographical 
names of the departure point and the destination point. The sectional 
display control means may further comprise means for additionally 
displaying a message representative of a section or means for additionally 
displaying a message representative of the geographical names of both end 
points of the selected section.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the drawings, in particular FIG. 1, there is shown one 
embodiment of an automotive navigation system according to this invention. 
This embodiment schematically shows a functional block diagram of this 
invention. In the figure, the outputs of a detecting means 1 for detecting 
the running distance of a vehicle, and a detecting means 2 for detecting 
the heading direction of the vehicle are connected to the inputs of a 
computing means 3 for computing the current position of the vehicle from 
the running distance provided by the detecting means 1 and the heading 
direction provided by the detection means 2. An initializing means 4 is 
provided for initially setting the current position of the vehicle for the 
computing means 3. A point information storage means 5 has stored therein 
information representative of a plurality of points each point consisting 
of a geographical name information and the positional information thereof. 
The point information storage means 5 is interconnected to a point setting 
means 6 which includes a key board for entering names representative of a 
departure (starting) point, a destination (goal) point, a passing 
(transit) point or passing points, namely, designates the respective 
geographical names of a departure point, a destination point and passing 
points on the way of the vehicle, reads out respective positional 
information corresponding to the entered geographical names from the 
storage means 5, and sets the positional information read out, according 
to the coordinates determined by the geographical names. On the basis of 
the mutual positional relationship between the departure point, the 
destination point and the passing points set by the point setting means 6, 
an all-points display control means 7 controls a display means 11 to 
display marks indicating all of the points at predetermined positions of 
the screen of the display means 11 and a mark indicating the current 
position of the vehicle on the screen on a reduced scale determined by the 
positions of the departure point and the destination point. A section 
setting means 8 serves to select two points, as desired, of the departure 
point, the destination point and the passing points and to set a section 
formed of the selected points. On the basis of the positional relationship 
of the two points set by the section setting means 8, a sectional display 
control means 9 controls the display means 11 to display the marks 
indicative of the points or selected by the section setting means 8 on 
predetermined positions of the screen of the displaying means 11 and to 
display the mark of the current position of the vehicle on the screen on a 
reduced scale determined by the positions of the selected marks. A display 
changeover means 10 selects one of the displaying contents of the 
all-points display control means 7 and the sectional display control means 
9 and provides the selected contents to the displaying means 11. As a 
result, it becomes possible to accurately determine positional location of 
the vehicle while driving, from the positional relationship of the marks 
indicative of the departure point, the destination point, the passing 
points and the current position of the vehicle displayed on the screen. 
The functional arrangement of this invention shown in FIG. 1 is 
specifically shown in FIG. 2 in the form of hardware. It is seen from FIG. 
2 that the hardware of this invention is formed of a running distance 
sensor 100, a vehicle heading sensor 200, a key board 300, a control 
circuit 400, a semiconductor memory 500 and a CRT 12. The distance sensor 
100 detects the rotational speed of a vehicle's wheel by means such as an 
electromagnetic pickup or a reed switch, and provides, as a detection 
output therefrom, pulses the frequency of which is proportional to the 
rotational speed of the vehicle's wheel to the control circuit 400. 
The heading sensor 200 detects the earth magnetism [H] (vector) being 
decomposed into a heading component Ha and the normal component Hb, as 
shown in FIG. 3, which is perpendicular to Ha by an earth magnetism 
detector 201 of a flux-gate type which is fixed on the vehicle 13, and 
outputs a signal corresponding to the detected magnetism to the control 
circuit 400. 
As illustrated in FIG. 4, the key board 300 includes a character key 
portion 301 and a control key portion 302. The character key portion 301 
consists of character keys representative of the "A" to "N" Japanese 
alphabet called "Kana", which have been represented and will be 
hereinafter represented by capital letters for the convenience's sake, as 
well as a voiced sound key represented by "V" and a semi-voiced sound key 
represented by "SV" which are utilized in combination with the character 
keys to generate the remaining Kana characters as shown in table in FIG. 
5. The control key group 302 consists of control keys indicative of 
"CLEAR", "SET", "DETURE POINT", "DESTINATION POINT", "PASSING POINT A", 
"PASSING POINT B", "COMPLETION", "ALL-POINTS", "SECTION", "SECTION CHANGE" 
and "START" functions. 
The character key board 301 is utilized to input all syllables known as 
"Kana" characters representative of all the syllables utilized in speaking 
Japanese. 
A Japanese "Kana" Table (alphabet) is shown in FIG. 5 in which all the Kana 
characters are represented by Roman characters. Specifically, the table 
comprises 44 CLEAR SOUND Kana characters from A to WA enclosed with a 
thick line in which rows 41a-41j are respectively called "A" row, "KA" 
row, "SA" row, "TA" row, "NA" row, "HA" row, "MA" row, "YA" row, "RA" row 
and "WA" row, respectively, an "N" SOUND Kana character shown in row 41k 
enclosed with a thick line, VOICED SOUND Kana characters shown in rows 
41m-41o, SEMI-VOICED SOUND Kana characters shown in row 41p, CONTRACTED 
SOUND characters shown in rows 41q-41w, VOICED CONTRACTED SOUND Kana 
characters shown in rows 41y-41z and SEMI-VOICED CONTRACTED SOUND 
characters shown in row 41zz. 
Next, the manner of inputting these Kana characters into the system using 
the keys 41 will be described. Referring to FIG. 4, a first column of keys 
41a1, 41a2, 41a3, 41a4, and 41a5 shown in FIG. 4 is utilized to enter the 
respective CLEAR SOUND Kana characters "A", "I", "U", "E" and "O" shown in 
row 41a in FIG. 5, a second column of keys represented by key 41b1 shown 
in FIG. 4 is utilized to enter the respective CLEAR SOUND Kana characters 
"KA", "KI", "KU", "KE" and "KO" shown in row 41b, and so on for the 
remaining CLEAR SOUND Kana characters as represented in the Kana table 
shown in FIG. 5 by the keys 41c1-41k. Key 41j1 represents the CLEAR SOUND 
Kana character "WA" while key 41k represents the Kana N. The key 410 is 
utilized in combination with the keys for generating the CLEAR SOUND 
characters to generate the VOICED SOUND characters. The key 412 is 
utilized in combination with the kys for generating the CLEAR SOUND Kana 
characters to generate the SEMI-VOICED SOUND Kana characters. For example, 
to generate the SEMI-VOICED SOUND PA, first the CLEAR SOUND key 
representative of the Kana SOUND "HA" is pressed after which the key 412 
is pressed, thereby changing the inputted sound from "HA to "PA". 
Similarly, the SEMI-VOICED SOUND Kana characters "PI", "PU", "PE" and "PO" 
are inputted by first inputting the respective CLEAR SOUND Kana characters 
"HI", "FU", "HE" and "HO", and then pressing the key 412, respectively. 
The VOICED SOUND Kana characters are inputted as follows. First a CLEAR 
SOUND KEY is pressed and then the key 410 is pressed. For example, to 
input the VOICED SOUND Kana character "GA", first the Kana character "KA" 
is inputted by pressing the corresponding CLEAR SOUND key, and then the 
key 410 is pressed to change the inputted Kana character from "KA" to 
"GA". Similarly, by pressing the key 410, inputted CLEAR SOUND Kana 
characters "KI", "KU", "KE" and "KO" can be changed to "GI", "GU", "GE", 
and "GO", the characters "SA", "SHI", "SU", "SE", and "SO" can be changed 
to "ZA", "JI", "ZU", "ZE" and "ZO", characters "TA", "CHI", "TSU", "TE" 
and "TO" can be changed to "DA", "JI", "ZU", "DE" and "DO", and characters 
"HA", "HI", " FU", "HE" and "HO" can be changed to "BA", "BI", "BU", "BE" 
and "BO", respectively. 
The Kana "N" can be entered upon pressing the key 41k. 
Next, the manner of entering tnhe CONTRACTED SOUND Kana characters will be 
described. For example, for entering the city name Kyoto, the CONTRACTED 
SOUND Kana "KYO" and the CLEAR SOUND "TO" must be inputted. To insert the 
Kana "KYO", first the key representative of the Kana "KI" is pressed after 
which the key representative of the Kana "YO" is pressed. Next, the key 
representative of the Kana "TO" is pressed, thereby inputting the word 
"KIYOTO". If no city "KIYOTO" exists in the memory, the system will 
automatically display the city KYOTO, whereby the CLEAR SOUNDS "KI" and 
"YO" are automatically changed to the CONTACTED SOUND Kana "KYO". 
Similarly, all the other CONTRACTED SOUND Kana can be generated by 
inputting the closest combination of CLEAR SOUND Kana. 
The lines I-IV shown in FIG. 5 joining the the CLEAR SOUND Kana rows to the 
VOICED SOUND Kana rows are indicative of the respective transformations 
which occur to the respective Kana when the key 410 is pressed and the 
line IV' indicates the transformation which occurs when the key 412 is 
pressed after the respective CLEAR SOUND Kana have been entered. 
The entry of Kana character by the activation of a key of the character key 
portion 41 is read in the control circuit 400. 
The semiconductor memory 500 is composed of, for example, a ROM (Read Only 
Memory) which has stored therein point information consisting of 
geographical name information (i.e. city names, town names, etc.) and the 
geographical position information thereof. The stored information is read 
out by the control circuit 400. 
For example, the point information of the city hall of HIMEJI (i.e. Himeji) 
City in Japan shown in FIG. 6A is stored in memories 501a-501g in a memory 
table of the semiconductor memory 500 illustrated in FIG. 7. In the 
memories 501a-501c, "HIMEJI" as a geographical information is sequentially 
stored in the form of the codes respectively representative of the 
Japanese "Kana" characters -HI", "ME", and "JI". It is to be noted that 
each of the memories comprises 8 bits. The most significant bits of each 
of the memories 501a-501c serves to indicate the information of a 
geographical name in which the memory 501c having stored therein the last 
character of the geographical name information is assigned "1" while the 
other memories 501a and 501b are assigned "0", as shown in FIG. 7. 
Therefore, the remaining seven bits of each of the memories 501a-501c 
represent a "Kana" character. With seven bits, it is possible to express 
all of the "Kana" characters having a clear sound, a voiced sound, a 
semi-voiced sound, a double sound, and a contracted sound, as illustrated 
in FIG. 5. The memories 501d-501g have stored therein the positional 
information of Himeji City in which the memories 501d and 501e serve to 
store the longitude of Himeji City while the memories 501f and 501g serve 
to store the latitude of Himeji City. Similarly, memories 502a-502g have 
stored therein the point information of, for example, "Kobe" (FIG. 6A) 
which is entered as "Koube" to expdress "Kobe" in a more accurate manner 
in Japanese. 
To obtain the positional information, coordinate axes X (East) and Y 
(North) may be set for the convenience's sake as shown by fthe map of 
Japan in FIG. 6B whereby geographical coordinates (x, y) represented by 
the relative distance on the basis of the coordinate axes may be stored in 
the memories. In this case, Japan is divided into 1700 Km squares in which 
this 1700 Km length is assigned 2 bytes (16 bits) of the memories 501d (or 
502d) and 501e (or 502e) for the abscissa (X-distance) and 2 bytes of the 
memories 501f (or 502f) and 501g (or 502g) for the ordinate. Therefore, 1 
bit is assigned about 26 m which results in a practical unit. 
Meanwhile, there exist about 680 cities all over Japan while by preparing 
about 300 geographical names including the names of wards, towns, 
villages, interchanges, stations, castles, lakes, passes, mountains, and 
peaks per one prefecture, about 13800 geographical names should be 
prepared in total for 46 divisions of Japan (including one Metropolitan 
District and 45 prefectures but not including Okinawa Prefecture). 
Supposing that the number of characters of a geographical name is five on 
the average, one point information requires 9 bytes (i.e. 5 bytes for a 
geographical name; 2 bytes for x coordinate (abscissa); 2 bytes for y 
coordinates (ordinate)) so that 124200 bytes are required to store 13800 
points of Japan. 
In order to store the information of 13800 points, there are required four 
ROM's each of which has the maximum storage capacity of 256K bits as 
commercially available at present. However, with a ROM of 1M bit which is 
expected to be commercially available in the near future, only one ROM 
would be sufficient, in which a small-sized, light, and highly reliable 
semiconductor memory can be utilized. 
The CRT 12 may comprise a conventional one and is assumed to have a 
rectangular screen 12a as shown in FIG. 8. It should be noted that 
coordinate axes U and V are perpendicular to each other to indicate screen 
coordinates (u, v) in the screen 12a on which the marks of a departure 
point, a destination point, passing points and the current position of the 
vehicle are to be indicated, as will be described later. 
The control circuit 400 comprises a well known micro-computer system, and 
includes various I/O interface circuits (not shown). The control circuit 
400 reads out the positional information from the semiconductor memory 500 
on the basis of the information of a geographical name which is entered by 
the activation of the key board 300, and causes the CRT 12 to display 
marks indicative of the points in an adequate reduced scale determined by 
the positional relationship between the departure point, the destination 
point and the passing points of the vehicle. Furthermore, the control 
circuit 400 inputs signals from the running distance sensor 100 and the 
heading sensor 200, computes the current position of the vehicle on the 
basis of said signals, and controls the CRT 12 to display a mark 
indicative of the current position of the vehicle in a predetermined 
reduced scale at the corresponding coordinates on the screen 12a. 
The operation of the control circuit 400 will now be described in detail 
with reference to flow charts illustrated in FIGS. 9A-9N. 
FIG. 9A illustrates the flow chart of a main routine of the program used 
for the control circuit 400. This general flow chart is started by an 
operation such as an electrical supply operation for the control circuit 
400. At Step S1, variables are initialized, and then, a subroutine S2 for 
a preparation processing for setting points, a subroutine S3 for a setting 
processing of a departure point, a subroutine S4 for a setting processing 
of a destination point, a subroutine S5 for a setting processing of a 
passing point A, a subroutine S6 for a setting processing of a passing 
point B, a subroutine S7 for a mark display control processing at the time 
of setting the points, a subroutine S8 for an initializing processing of 
the current position, a subroutine S9 for a diasplay changeover 
(all-points display/sectional display) control processing and a subroutine 
S10 for a section setting processing are sequentially executed repeatedly. 
More specifically, an operator depresses the "CLEAR" key of the key board 
300 before setting a departure point and a destination point. 
Consequently, in a flow chart of FIG. 9B illustrating the details of the 
subroutine S2 for the preparation processing of the point setting, the 
above depression of the key is detected at Steps S21 and S22, and then 
memories Pn, X, Y, Xn, Xs, Ys, Gn, Xg, and Yg (not shown), which will be 
described later, for setting respective points are all cleared and a 
memory K for storing section numbers, which will be also described later, 
is set to "1" at Step S23. 
Then, a departure point is entered, that is, when for example, "Himeji 
City" is to be set, the "DETURE POINT", "HI", "ME", "SHI", "V" (key 
410) and "SET" keys on the key board 300 are sequentially depressed. 
Consequently, in a flow chart of FIG. 9C illustrating the details of the 
subroutine S3 for the setting processing of the departure point shown in 
FIG. 9A, the depression of the "DETURE POINT" key is first detected at 
Steps S31 and S32 whereby a subroutine S33 for a geographical name 
entering processing and a point retrieving processing is executed. At Step 
S301 in a flow chart in FIG. 9D illustrating the details of the subroutine 
S33, the contents of the entered key are read in, and when the contents of 
the entered key are found to be characters at Step S302, they are stored 
in the memory Pn (n=1, 2, - - - ) for storing the characters of 
geographical names. Every time a character key is depressed once, Steps 
S301-S303 are executed so that "HI" is stored in a memory P1, "ME" in a 
memory P2, "SHI" in a memory P3, and "V" in a memory P4, respectively, the 
memories P1-P4 being not shown. Finally, the depression of the "SET" key 
is detected at Steps S302 and S304, and at Step S305 the combination of 
the entered characters "HI", "ME", "SHI", and "V" is retrieved from the 
semiconductor memory 500 whereby a point information having the 
combination of the characters "HI", "ME", "SHI" and "V" (the combination 
of "SHI" and "V" is regarded as "JI" on this retrieval) stored in the 
memories 501a-501g is retrieved and at S306 the positional information of 
the point information stored in the memories 501d-501g is read out. The 
contents of the memories 501d and 501e are stored in the memory X while 
the contents of the memories 501f and 501g are stored in the memory Y. 
Then, the program returns to Step S34 in the flow chart of FIG. 9C where 
the entered information of the geographical name in the memory Pn and the 
retrieved positional information in the memories X and Y are respectively 
transferred to the memories Sn (n=1, 2, - - - ), Xs, and Ys and are 
representative of a departure point. Hereby, the setting processing of the 
subroutine S3 for the departure point has been completed. 
It is to be noted that the contents of the memories Sn (n=1, 2 - - - ), Xs, 
and Ys respectively denote the geographical name of the departure point, 
the X coordinate value of the positional information of the departure 
point, and the Y coordinate value of the positional information of the 
departure point. 
Next, a destination point is entered in the subroutine S4 shown in FIG. 9A. 
When for example, city Kobe which is identical to Koube in Japanese is 
selected, the "DESTINATION POINT", "KO", "U", "HE", "V" keys (key 410), 
and "SET" on the key board 300 shown in FIG. 4 are sequentially depressed. 
Consequently, in FIG. 9E illustrating the detailed flow chart of the 
subroutine S4, the activation of the "DESTINATION POINT" key is detected 
at Steps S41 and S42, and then the proram proceeds to Step S43 which 
corresponds to Step S33 in FIG. 9C so that the description thereof will 
not be repeated. After the execution of Step S43, at Step S44 the 
information of the geographical name in the memory Pn, and the retrieved 
positional information in the memories X and Y are respectively 
transferred to the memories Gn, Xg, and Yg for the destination point. It 
is to be noted that the contents of the memories Gn (n=1, 2 - - - ), Xg, 
and Yg respectively denote the geographical name of the departure point, 
the X coordinate value of the positional information of the destination 
point, and the Y coordinate value of the positional information of the 
destination point. 
Thus, after the execution of the setting processing of the destination 
point (subroutine S4) has been completed, passing points, e.g. Kakogawa 
City and Akashi City (shown in FIG. 6A) which the vehicle 13 transmits 
while running from the departure point to the destination point are set in 
the same process as the subroutine S3 for the departure point setting 
processing. Namely, as illustrated in the flow chart of FIG. 9F 
corresponding to the subroutine S5 for the passing point A setting 
processing, the activation of "PASSING POINT A" key is detected at Steps 
S51 and S52, and then at Step S53 which corresponds to Step S33 
illustrated in FIG. 9C or Step S43 illustrated in FIG. 9E, the 
geographical name of "Kakogawa" is entered and the point information 
thereof is retrieved, whereby the passing point A is set at Step S54. It 
is to be noted that the contents stored in the memories An (n=1, 2 - - - 
), Xa, and Ya respectively denote the geographical name of the passing 
point A, the X coordinate (abscissa) value of the positional information 
of the passing point A, and the Y coordinate (ordinate) value of the 
positional information of the passing point A. 
Next, as illustrated in the flow chart of FIG. 9G corresponding to the 
subroutine S6 for the passing point B setting processing, the activation 
of "PASSING POINT B" key is detected at Steps S61 and S62, and then at 
Step S63 which corresponds to Step S33 illustrated in FIG. 9C or Step S43 
illustrated in FIG. 9E, the geographical name of "Akashi" is entered and 
the point information thereof is retrieved, whereby the passing point B is 
set at Step S64. It is to be noted that the contents stored in the 
memories Bn (n=1, 2 - - - ), Xb, and Yb respectively denote the 
geographical name of the passing point B, the X coordinate (abscissa) 
value of the positional information of the passing point B, and the Y 
coordinate (ordinate) value of the positional information of the passing 
point B. 
It is also to be noted that while the above embodiment limits the number of 
passing points to two, one or three or more passing points may be readily 
set by the addition of subroutines such as the subroutine S5 or S6. 
After the settings of the departure point, the destination point and the 
passing points A and B have been thus processed, the operator depresses 
the "COMPLETION" key. Consequently, the subroutine S7 for the mark display 
control processing at the time of settng the points illustrated in FIG. 9A 
will be executed along a flow chart illustrated in FIG. 9H. In this flow 
chart, at Steps S71 and S72, the depression of the "COMPLETION" key is 
detected. Then, as will be described hereinafter, a reduced scale is 
determined such that marks respectively indicative of the departure point, 
the passing points A and B, and/or the destination point may be displayed 
on the periphery 12c of a rectangular zone 12b, having a lateral length of 
lx and longitudinal length of ly, preliminarily imaginarily set on the 
screen 12a of the CRT 12 shown in FIG. 8. 
Namely, first of all, at Step S73, maximum values Xmax, Ymax and minimum 
values Xmin, Ymin are determined from every component (abscissa, ordinate) 
of the coordinates respectively of the departure point, the destination 
point and the passing points. In this embodiment as shown in FIG. 6A where 
the departure point is Himeji City, the destination point is Kobe City, 
and the passing points A and B are Kakogawa City and Akashi City 
respectively, the following values are given: 
Xmax=Xg 
Xmin=Xs 
Ymax=Ys 
Ymin=Yb 
Then, a subroutine S74 for the processing of the computation of the 
coordinates is executed along a flow chart illustrated in FIG. 9I. In this 
flow chart, at Step S701, the ratio of the lateral length lx of the 
rectangular zone 12b of the screen 12 to a distance (Xmax-Xmin) in the 
lateral direction (from East to West) between the maximum value Xmax and 
the minimum value Xmin on the abscissa X is determined as 
rx=lx/(Xmax-Xmin)=lx/Xg-Xs), and the ratio of the longitudinal length lx 
of the rectangular zone 12b of the screen 12 to a distance (Ymax-Ymin) in 
the longitudinal direction (from North to South) between the maximum value 
Ymax and the minimum value Ymin of the ordinate Y is determined as 
ry=ly/(Ymax-Ymin)=ly/(Ys-Yb). Then, at Step S702, the magnitudes of the 
above ratios rx and ry are compared. If rx.ltoreq.ry, rx is determined to 
be a reduced scale r while if rx&gt;ry, ry is determined to be the reduced 
scale r (Steps S703, S704). It is to be noted that this embodiment gives 
rx&lt;ry as seen from FIG. 6A so that rx is selected as the reduced scale r. 
Then, at Step S705, the coordinates (Xo, Yo) of the middle point of the 
coordinate values Xmax, Ymax and Xmin, Ymin are calculated on the basis of 
the following equations: 
EQU Xo=(Xmax+Xmin)/2 
EQU Yo=(Ymax+Ymin)/2 
and in order that the middle point may correspond to the central point, 
i.e. the origin (u=0, v=0), of the rectangular zone 12b, the conversion of 
the coordinates and the reduction of the reduced scale are calculated at 
Step S706 on the basis of the following equations: 
EQU Us=r(Xs-Xo) 
EQU Vs=r(Ys-Yo) 
EQU Ug=r(Xg-Xo) 
EQU Vg=r(Yg-Yo) 
EQU Ua=r(Xa-Xo) 
EQU Va=r(Ya-Yo) 
EQU Ub=r(Xb-Xo) 
EQU Vb=r(Yb-Yo) 
EQU up=r(xp-Xo) 
EQU vp=r(yp-Yo) 
where the coordinate values Xs, Ys, Xg and Yg respectively indicate the 
contents of the memories Xs, Ys, Xg and Yg, (Us, Vs) represents the 
coordinates of the departure point on the screen 12a, (Ug, Vg) represents 
the coordinates of the destination point on the screen 12a, (Ua, Va) and 
(Ub, Vb) represent the coordinates of the passing points A and B, 
respectively, and (up, vp) represents the coordinates of the current 
position of the vehicle. In this way, the coordinates of the departure 
point and the destination point are respectivey positioned on the outer 
periphery 12c of the rectangular zone 12b. It should be noted that, as can 
be seen from step S73, if one of the points Xmax, Xmin, Ymax, Ymin 
corresponds to one or both of the passing points A and/or B, the 
calculation of the middle point Xo, Yo will be based thereon, and, 
accordingly the two points appearing on the outer periphery 12C will not 
be the departure point and destination point, but one of the passing 
points and either the other passing point, the departure point or the 
destination point. The calculation of the coordinates (up, vp) of the 
current position of the vehicle on the screen 12a after the vehicle has 
started will be described later. 
Thus, the execution of the subroutine S74 for the processing of the 
coordinate calculation has been completed, and then the program returns to 
Step S75 in FIG. 9H in which a display signal is outputed to the CRT 12 
from the control circuit 400 so that a mark 901 of the departure point, a 
mark 902 of the destination point, and marks 903 and 904 respectively 
indicative of the passing points A and B may be displayed on the screen 
12a, shown in FIG. 10A, at the calculated coordinates (Us, Vs), (Ug, Vg), 
(Ua, Va), and (Ub, Vb) respectively of the departure point, the 
destination point, the passing points A and B. Thus, the execution of the 
subroutine S7 of FIG. 9A hs been completed. 
When the vehicle is positioned at the departure point set, the operator may 
immediately depress the "START" key on the key board 300. If the vehicle 
is positioned a little far from the coordinates of the departure point, 
the operator may depress the "START" key when the vehicle has reached the 
geographical coordinates (Xs, Ys) which corresponds to the coordinates 
(Us, Vs) on the screen 12a of the departure point. According to this, the 
subroutine S8 for the initializing processing of the current position of 
the vehicle illustrated in FIG. 9A will be executed along a flow chart 
illustrated in FIG. 9J. In this flow chart, at Steps S81 and S82, the 
depression of the "START" key is detected, and then at Step S83 the 
geographical coordinates (Xs, Ys) of the departure point are set in 
memories "xp" and "yp" (not shown), for the coordinates of the current 
position of the vehicle, used for an integral computation of the current 
position of the vehicle. 
Thus, with the settings of the departure point, the destination point, and 
the current position of the vehicle having been completed and with the 
vehicle being continuously driven, an interrupt command is inputted to the 
micro-computer of the control circuit 300 each time the running distance 
sensor 100 generates a pulse at an interval of a unit running distance dl 
(for example, 1 m), thereby executing an interrupt processing shown in 
FIG. 9K. 
In the flow chart of FIG. 9K, heading signals Ha and Hb are read in by the 
micro-computer of the control circuit 300 at Step S801, and an angle 
.theta. derived from the earth magnetism [H] (vector) shown in FIG. 3 and 
the vehicle's heading 13a is calculated at Step S802 from the following 
equation: 
EQU .theta.=tan.sup.-1 (Hb/Ha) 
Then, heading components dx and dy of the unit running distance d1 with 
respect to the coordinate axes X and Y shown in FIG. 6B are calculated at 
Step S803 according to the following equations: 
EQU dx=dl sin .theta. 
EQU dy=dl cos .theta. 
and are added to the values integrated so far in the memories xp and yp of 
the coordinate components of the current position of the vehicle at Step 
S804. 
Then, at Step S805, the coordinates (up, vp) of the current position of the 
vehicle on the screen 12a are calculated according to the following 
equations: 
EQU up=r(xp-Xo) 
EQU vp=r(yp-Yo) 
on the basis of the reduced scale r, and then at Step S806, a display 
signal is outputtted from the control circuit 300 to the CRT 12 so that a 
mark 905 indicative of the current position of the vehicle may be 
displayed as shown in FIG. 10B at the coordinates (up, vp) on the screen 
12a. 
While the displaying operation shown in FIG. 10B is being done, when a 
driver further desires to known the positional relationship between the 
departure point, the passing point A, and the current position of the 
vehicle, he may operate the system as follows: 
Namely, when the "SECTION" key of the control key portion 302 of the key 
board 300 is depressed, the processing for magnifying the display of a 
section between the departure point and the passing point A is executed in 
accordance with the subroutine S9 for the display changeover control 
(all-points displaying control/sectional displaying control) processing in 
FIG. 9A. It is to be noted that in this embodiment, a geometrical section 
between the departure point and the passing point A is defined as a first 
section, a geometrical section between the passing points A and B is 
defined as a second section, and a geometrical section between the passing 
point B and the destination point is defined as a third section. 
The subroutine S9 is illustrated in detail in the flow chart of FIG. 9L in 
which at Steps S91, S92, S96 the activation of the "SECTION" key is 
detected to execute the subroutine S97 for the sectional displaying 
control processing. 
FIG. 9M illustrates the flow chart of the subroutine S97 in FIG. 9L in 
which at Step S901 the value of a section number K indicating whether or 
not a section where the vehicle is positioned is K is checked. If K=1, 
then the program proceeds to Step S902, if K=2, then the program proceeds 
to Step S905, and if K=3, then the program proceeds to Step S908. It is to 
be noted that at first the value of the section number K is set to "1" as 
its initial value at Step S23 in FIG. 9B, as previously set forth. 
Therefore, Step S902 is executed, in which the maximum values Xmax, Ymax, 
and the minimum values Xmin, Ymin among the coordinates values 
respectively of both end points in the first section, i.e. the departure 
point and the passing point A are determined. In this embodiment shown in 
FIG. 6A, 
EQU Xmax=Xa 
EQU Xmin=Xs 
EQU Ymax=Ys 
Ymin=Ya 
After these values have been determined, the subroutine S903 for the 
coordinate calculation processing is executed. Since the subroutine S903 
(and S906, S909) is identical with the subroutine S74 in FIG. 9H, the 
description thereof will not be repeated. 
Then, at Step S904, marks indicating the points of the departure point, the 
passing point A, and the current position of the vehicle are respectively 
displayed at the coordinates of (Us, Vs), (Ua, Ub), (up, vp), on the 
screen 12a of the CRT 12, which are computed by the subroutine S903. As 
shown in a display example in FIG. 10C, such a simple operation as 
indicated above can readily achieve a magnified display (also called a 
sectional display) of a required portion. 
While the display shown in FIG. 10C is appearing, when the driver desires 
to restore the display state of FIG. 10B, the operation should be as 
follows: 
When the "ALL-POINTS" key of the key board 300 is depressed, the depression 
of this key is detected at Steps S91 and S92 in the flow chart of FIG. 9L 
executing the subroutine S9, and then at Steps S93 and S94 which are 
respectively identical with Steps S73 and S74 in FIG. 9H, the coordinates 
on the screen 12a of the departure point, the destination point, the 
passing points A and B, and the current position of the vehicle are 
computed, and then at Step S95 the marks of all the points as well as the 
current position are displayed at the computed coordinates. Consequently, 
the displaying state returns to the state of FIG. 10B. It is to be noted 
that in FIG. 9L, Step S91, S92, or S96 coordinates to the display 
changeover means 10 in FIG. 1, Step S93, S94, or S95 corresponds to the 
all-points display control means 7 in FIG. 1, Step S97 corresponds to the 
sectional displaying control means 9, and the flow chart of FIG. 9N 
illustrating the subroutine S10 corresponds to the section setting means 
8. 
When the vehicle 13 continues to run and the displaying state of the screen 
12a of the CRT 12 assumes the state of FIG. 10D, the "SECTION" key on the 
key board 300 is depressed in order to display in detail the positional 
relationship between the passing point A, the passing point B, and the 
current position of the vehicle, whereby the processing S97 of the 
sectional displaying control as set forth above is to be executed. 
However, in the flow chart illustrated in FIG. 9M which shows the details 
of the subroutine S97, the section number K remains unchanged as 1 at Step 
S901 so that Steps S902-S904 for a sectional display in the first section 
are again executed unfavourably. Therefore, in order to make a sectional 
display in the second section as desired, the following operations should 
be carried out: 
If it is assumed that the "SECTION" key has been already depressed and the 
sectional display in the first section is being made, when the "SECTION 
CHANGE" key is depressed, the subroutine S10 for the section setting 
processing in FIG. 9A is executed as follows: In the flow chart in FIG. 9N 
illustrating the subroutine S10, it is firstly determined at Step S101 
whether or not the section is being displayed on the screen 12a. If the 
section is displayed, then at Steps S102 and S103 the depression of the 
"SECTION CHANGE" key is detected and then at Step S104 the value of the 
section number K is increased by 1. It is to be noted that the section 
number K is set at Steps S105 and S106 such that if it reaches 4, it is 
reset to 1 again. Finally, at subroutine S107 which is identical with the 
subroutine S97 in FIG. 9L, the processing of the section display control 
is carried out. 
As above described, the section number K has been changed to 2 by the 
execution of Step S104 and therefore, in the flow chart of FIG. 9M 
illustrating the subroutine S107 in FIG. 9N the program proceeds to Step 
S905 through Step S901. In this Step S905, the maximum values Xmax, Ymax, 
and the minimum values Xmin, Ymin along the coordinates respectively of 
both end points, i.e. the passing points A and B are determined, and then 
the subroutine S906, which is identical with the subroutine S903, for the 
coordinate computation processing is executed, and then at Step S907 the 
marks respectively indicating the passing points A, B and the current 
position of the vehicle are displayed on the screen 12a of the CRT 12, as 
shown in FIG. 10E. 
Thus, by activating the "SECTION CHANGE" key while a section is being 
displayed, a magnified display can be made by selecting a desired section 
from among the first to third sections. It is to be noted that Steps 
S908-S910 in FIG. 9M perform the processing of the sectional display of 
the third section in which Step S908 corresponds to Step S902 or S905, 
Step S909 is identical with Step S903 or S906, and Step S910 corresponds 
to Step S904 or S907, whereby the passing point B, the destination point 
and the current position are displayed as the respective marks. 
While in this embodiment a section between two adjacent points has been 
used, a section bridging, for example, three points may be used with the 
same sectional display processings as follows: 
Departure point-passing point A-passing point B: a first section. 
Passing point A-passing point B-destination point: a second section. 
In accordance with the arrangement of the system of this invention, when a 
departure point, a destination point, and passing points of a vehicle are 
designated by their geographical names, the control circuit 400 reads out 
the positional information of a desired point from the point information 
as previously stored. The positional information is set as the coordinates 
of the points which are displayed with respective marks on an adequate 
reduced scale on the CRT and the current position of the vehicle which is 
computed every second is displayed by a respective mark. Furthermore, a 
selection (changeover) may be made between all-points display and a 
sectional display as desired. Consequently, a system having preferable 
navigation functions suitable for boarding on an automobile is provided as 
follows: 
(1) The picture information of an actual map is not stored in the 
semiconductor memory but instead point information consisting of the 
information of given points is stored as a basic unit whereby the 
information of points over a wide range of areas can be stored. 
(2) Since a departure point and a destination point are designated by their 
geographical names and the positional information previously stored is 
read out and set as the coordinates of the points, the positions of the 
points can be accurately set with easy operations. 
(3) Since the marks 901-904 indicative of the points are displayed on 
adequate positions of the screen 12a on the basis of the distance between 
the departure point and the destination point and of the positional 
relationship therebetween and the mark 905 indicative of the current 
position of the vehicle is displayed on a reduced scale determined by the 
marks 901-904, the operator can devote his entire energy to driving the 
vehicle without having to perform cumbersome operations such as the 
settings of the positions of the marks and the reduced scale. 
(4) Since a display on the screen 12a of the CRT is divided into an 
all-point display for displaying all of the departure point, the 
destination point, and the passing points as set and a sectional display 
for displaying two adjacent points of all of the points in which both of 
the displays may be changed over, it is possible to grasp the positional 
relationship between the points and the current position of the vehicle in 
a displaying manner as desired. 
It is to be noted that while the above embodiment of this invention has 
dealth with a semiconductor memory such as a ROM as a point information 
storage means, if a storage of a large capacity such as a floppy disc is 
used, then more positional information can be stored. Also, a voice input 
device may be substituted for a key board. Furthermore, a liquid crystal 
display device of a dot-matrix type may be substituted for a CRT. 
Next, there will be described another display example on the CRT 12 in 
accordance with this invention. In FIG. 11A, a message "ALL-POINTS" is 
displayed below the rectangular zone 12c of the screen 12a which shows all 
of the points entered as in FIG. 10B so that an operator may identify the 
display as showing all of the points entered. This display processing can 
be readily carried out by the addition of a displaying Step S76 or S98 
enclosed by a dotted line, which is quite common to those skilled in the 
art, immediately after Step S75 in FIG. 9H or Step S95 in FIG. 9L, 
respectively. Also, in FIG. 11B, a message "SECTION" is displayed below 
the rectangular zone 12c of the screen 12a which only shows two of all of 
the points entered as in FIG. 10C so that an operator may identify the 
display as showing a sectional one. This display processing may be also 
carried out by the addition of a displaying Step S912 enclosed by a dotted 
line immediately after Step S904, S907, or S910 in FIG. 9M. 
Thus, with the addition of a message of "ALL-POINTS" or "SECTION" to a 
display on the screen 12a, the operator will not erroneously recognize the 
status of the display upon selecting "ALL-POINTS" and "SECTION" keys of 
the control key portion 302 of the key board 300. 
In FIGS. 12A and 12B, there are shown further different display examples 
according to the present invention in which, in FIG. 12A, above the 
rectangular zone 12c of the screen 12a for all of the points entered such 
as shown in FIG. 10B, the geographical names "Himeji City" and "Kobe City" 
respectively representing the departure point and the destination point 
are displayed on either side of an arrow displayed in the direction as 
shown in FIG. 12A. This display processing may be carried out by Step S76 
or S98 immediately after Step S75 in FIG. 9H or Step S95 in FIG. 9L, 
respectively. Also, in FIG. 12B, the sectional display screen 12a shown in 
FIG. 10C is added with the geographical names "Himeji City" and "Kakogawa 
City" respectively representing the departure point and the passing point 
A. This display processing may be carried out by Step S912 immediately 
after Step S904, S907, or S910 in FIG. 9M. 
Thus, with the geographical names of the departure point and the 
destination point being displayed during the displaying of all-points, or 
with the geographical names of the end points of a section set for a 
sectional display being displayed, the operator can easily recognize the 
geographical names of the points being displayed by the marks at any given 
time. 
As described above, in accordance with this invention, a storage means has 
stored therein point information consisting of the information of the 
geographical name of the point as well as the geographical position of the 
point and a departure point, a destination point, the current position and 
passing points of a vehicle are displayed as respective marks at 
coordinates determined by those points according to the point information. 
Therefore, even a storage of a small capacity can be used as a data 
storage means capable of fully displaying the current position of the 
vehicle. Moreover, since the all-points display and the sectional display 
can be changed over therebetween as desired by simple operations, the 
current position of the vehicle can be accurately displayed. As a result, 
an on-board automotive navigation system, which is compact and cheap, 
having a fully practical navigation function is realized. 
It is to be noted that while the present invention has been described with 
reference to the above embodiments illustrated in the accompanying 
drawings, it should not be limited to them and may be applied with various 
modifications thereof without departing from the spirit of the invention.