Satellite navigation system of which map data are partially updateable

[0002] 1. Field of the Invention

[0003] The present invention relates to a satellite navigation system comprising a server and on-vehicle navigating terminals communicably connected to the server via a communication network, wherein map data supplied to the navigating terminals are partially updateable.

[0004] 2. Description of Related Art

[0005] In recent years, a satellite navigation system has become popular. The satellite navigation system guides a user (driver) to a user's desired destination with a map shown on a navigating terminal. A practical configuration of such satellite navigation system is configured as now described. In response to a user's request, map data stored in a server placed at a map data base site are transmitted to such a navigating terminal as an on-vehicle navigation unit, mobile navigation unit, PDA (personal digital assistants), or mobile phone, through communication means. The communication means is composed of for example a computer network (e.g., the Internet) or a mobile communication network. The navigating terminal includes a GPS (global-positioning system) to detect a vehicle's current position, and provides a map on a monitor thereof using both the vehicle's current position and the received map data.

[0006] Such a satellite navigation system is advantageous in that it is able to enable each navigating terminal (i.e., a user) to make reference to the newest versions of maps. In order to gain the advantage, a user has to have the newest map data by reloading map data stored in a block in the navigating terminal, whatever the map data handled in the server is updated.

[0007] Practically, in each navigating terminal participating in the satellite navigation system, all the map data in one block should be downloaded to renew the map data when the map data is updated in the server.

[0008] However, in the conventional satellite navigation system, even when a unit of map data is partially updated in the server, the entire map data in each block should be downloaded due to the above downloading way on the one-block basis. As a result, amounts of data to be reloaded become extremely large, resulting in that a communication load imposed on a communication line becomes high as well. This necessitates a longer time to process map data in the reloading operation and a high communication cost.

[0009] The present invention has been made in view of the above circumstances. An object of the present invention is, therefore, to greatly reduce an amount of data to be re-loaded so that a load imposed on a communication line can be lowered when map data is updated.

[0010] The present invention is reduced into practice in various aspects, such as a server incorporated in a satellite navigation system, a terminal in the system, and a method of updating map data in the system.

[0011] In order to achieve the above object, as one aspect of the present invention, there is provided a method of updating map data in a satellite navigation system comprising a server storing the map data to be used by a navigating terminal to perform navigation; the method comprising the steps of: causing the server to produce the map data divided into a plurality of sets of map data that are mutually-independent set by set; causing the server to transmit, to the navigating terminal, information including a set of updated map data; and causing the navigating terminal to use the received set of updated map data to update map data temporarily stored in the navigating terminal for the navigation.

[0012] Further, it is preferred that the information to be transmitted from the server to the terminal includes information indicating a type of operation to be carried out by the terminal for the update.

[0013] As a result, in the server, the map data can be updated partially, that is, every set of divided data map, in an easier manner. This partially updateable configuration is also effective in reloading map data from the server to each navigating terminal. For reloading the map data, it is sufficient that only one or more sets of map data that has been updated are delivered from the server to the navigating terminal. Hence an amount of map data to be downloaded can be reduced greatly. Each navigating terminal is therefore able to update, set by set, map data temporarily stored for navigation by using both of only the received set of map data and the operation of a specified type. Therefore, for updating the map data used in each navigating terminal, a communication load imposed on the communication means can be lessened noticeably.

[0014] Further, because the map data are divided into a plurality of sets independent of each other, each certain set of map data can be replaceable with no effect on the other sets of map data in terms of data connections.

[0015] According to another aspect of the present invention, there is provided a server for storing map data to be supplied to a terminal for performing navigation, both of the server and the terminal being incorporated in a satellite navigation system, the server comprising: a storage for storing the map data divided into a plurality of sets of map data that are mutually-independent set by set; an updating unit configured to update, every set of the divided map data, the map data stored in the server; and a transmitting unit configured to transmit, to the navigating terminal, information including a set of updated map data.

[0016] As a result, when the map data used in each navigating terminal is updated, a communication load imposed on the communication means can be lessened noticeably, because it is enough that only a set of map data that has been updated is transmitted from the server to each navigating terminal via the communication means.

[0017] It is also preferred that the information to be transmitted from the server to the terminal includes information indicating a type of operation to be carried out by the terminal for the update. This transmission enables each navigating terminal to perform more complicated updating operations in an easier way.

[0018] By way of example, the type of operation to be carried out by the terminal is one selected from a group of processes including replacing the entire map data with new data, partially replacing the map data by new data, partially deleting map data from the map data, and partially adding new map data to the map data, the partially replacing, partially deleting, and partially adding operations being carried out set by set.

[0019] It is also preferred that the map data consists of different kinds of map data formed into a layered structure of map data. Practically, as one example, the layered structure of map data includes a first layer formed by data of a plurality of objects, a second layer formed by a plurality of blocks, each block consisting of one or more objects of the same kind, and a third layer formed by a plurality of layers, each layer consisting of data of a plurality of blocks for the same type of depiction of map data. For example, each set of the map data is composed of one of each layer of map data, each block of map data, and each object of map data.

[0020] The above layered structure of map data makes it easier to divide entire map data into a plurality of sets of map data classified according to their natures.

[0021] Still, according to another aspect of the present invention, a recording medium for storing map data is provided, which is incorporated in a server of a satellite navigation system, the map data being divided into a plurality of sets of map data that are mutually-independent set by set, updateable every set of the divided map data, and configured to have different kinds of map data formed into a layered structure of map data, wherein the layered structure of map data includes a first layer formed by data of a plurality of objects, a second layer formed by a plurality of blocks, each block consisting of one or more objects of the same kind, and a third layer formed by a plurality of layers, each layer consisting of data of a plurality of blocks for the same type of depiction of map data. By using this recording medium, the server is able to provide a configuration in which map data for navigation can be updated partially.

[0022] Still, according to another aspect of the present invention, there is provided a navigating terminal for performing navigation based on map data supplied from a server through communication means, both of the server and the terminal being incorporated in a satellite navigation system, the navigating terminal comprising: a receiving unit configured to receive, from the terminal though the communication means, information including a set of updated map data and selected from the map data divided into a plurality of sets of map data that are mutually-independent set by set; an updating unit configured to update map data temporarily stored in the terminal for the navigation, by using the received information including the set of updated map data.

[0023] Preferably, the information to be received from the server includes information indicating a type of operation to be carried out by the terminal for the update. It is also preferred that the type of operation to be carried out by the terminal is one selected from a group of processes including replacing the entire map data with new data, partially replacing the map data by new data, partially deleting map data from the map data, and partially adding new map data to the map data, the partially replacing, partially deleting, and partially adding operations being carried out set by set.

[0024] It is therefore enough for each navigating terminal to update the stored map data using only one or more received sets of map data. An amount of data that is involved in the update processing is reduced largely compared to the conventional. A load to calculate data by each navigating terminal diminishes as well, thus making the update faster and reducing a cost of the update.

[0025] Other objects and aspects of the present invention will become apparent from the following description and embodiments with reference to the accompanying drawings in which:

[0026] FIG. 1A shows the entire block diagram of a navigation system according to an embodiment of the present invention;

[0027] FIG. 1B details the block diagram of a server incorporated in the navigation system;

[0028] FIG. 1C details the block diagram of a terminal incorporated in the navigation terminal;

[0029] FIG. 2 is a flowchart showing processing for retrieving a map in the embodiment;

[0030] FIG. 3A is a flowchart showing processing for computing a desired route, which is carried out as part of route processing according to the embodiment;

[0031] FIG. 3B is a flowchart showing processing for guiding the route, which is carried out as part of route processing according to the embodiment;

[0032] FIG. 4 shows a flowchart for information retrieval processing according to the embodiment;

[0033] FIGS. 5A and 5B pictorially illustrates the structures of map data stored in a storage of the server;

[0034] FIG. 6 pictorially illustrates a replacement of one layer using the map data shown in FIGS. 5A and 5B;

[0035] FIG. 7 pictorially illustrates a deletion and an addition of blocks using the map data shown in FIGS. 5A and 5B;

[0036] FIG. 8 explains processing required for the delivery of map data from the server to a certain terminal;

[0037] FIG. 9 shows the format of a header for map data in the server; and

[0038] FIG. 10 shows a format for updating operations carried out in the server.

[0039] A preferred embodiment according to the present invention will now be described with reference to accompanying drawings.

[0040] In the following embodiment, a satellite navigation system to which the present invention is applied will now be described. The satellite navigation system includes on-vehicle terminals, a server, and a network such as the Internet connecting the server to the terminals, in which both of the terminals and the server are able to communicate to each other through the network. The satellite navigation system is able to give guide information to a user on a vehicle on which each terminal is mounted.

[0041] (I) Entire Configuration and its Operations

[0042] First, referring to FIGS. 1A to 1C, to 4, the entire configuration and its operations of a navigation system according to the present embodiment.

[0043] FIGS. 1A to 1C show in block forms the configurations of the navigation system, while FIGS. 2 to 4 show navigation processing performed by the navigation system.

[0044] As shown in FIG. 1A, the satellite navigation system S is equipped with plural terminals T mounted on users' vehicles, the Internet IN serving as communication means, and a server SV serving as a control for the entire system.

[0045] Each terminal T is configured to send a terminal signal St through the Internet IN to the server SV and receive another terminal signal St from the server SV. The terminal signal St sent from each terminal T to the server SV includes pieces of information for requesting information concerning the current position and current driving direction of a vehicle as well as information that should be provided to a driver on the vehicle. Further, the terminal information St sent from the server SV to each terminal T is composed of various types of information necessary for navigating processing sent through the Internet IN in response to the request information.

[0046] The server SV is configured to receive, as a server signal Ssv, the terminal signal St sent from each terminal T by way of the Internet IN. Based on the server signal Ssv, the server SV performs various kinds of processing, which includes, as will be detailed later, processing to retrieve various kinds of information, such as map data, that will be presented on a certain terminal T for user's viewing and processing to retrieve a guide route for each terminal-mounted vehicle. In addition, the server SV sends out, as another server signal Ssv, results of the processing to a specified terminal T via the Internet IN. Incidentally, the server SV has the capacity of transmitting and receiving necessary information to and from a plurality of terminals T on the basis of, for example, a time sharing technique.

[0047] The server SV and each terminal T will now be detailed in terms of their configurations.

[0048] As shown in FIG. 1B, the server SV is equipped with a CPU 1 responsible for control means, a display 2, an input device 3, a storage 4 composed of a hard disk unit and others, which serves as individual information registering means, and an interface 5.

[0049] The interface 5 is formed to perform predetermined processing as an input interface on the server signal Ssv sent through the Internet IN so that a processing server signal Sc is outputted from the interface 5 to the CPU 1. Further, the interface 5 performs predetermined processing as an output interface on the processing server signal Sc sent from the CPU 1 to each terminal T so that a server signal Ssv is provided to the terminal T via the Internet IN.

[0050] The storage 4 memorizes various type of information necessary for navigation processing executed in this embodiment. Such information includes map information to be displayed on the terminal T, a variety of kinds of information used for route processing described later, spot information required for performing navigation processing, and individual information about each user who uses the terminal T. The spot information further includes positional information in relation to spots to be indicated on a map displayed by the terminal T and content information that explains each spot. These pieces of information are outputted from this storage 4 to the CPU 1, as a memory signal Sm, when they are requested. The storage 4 constitutes individual information registering means of the present invention.

[0051] The CPU 1 is functionally composed of a map outputting element 1a, route processing element 1b, and retrieving element 1c. Of these constituents, the map outputting element 1aresponds to the request information, that is, the processing server signal Sc that has been received. Practically, this element 1aretrieves all the pieces of map information stored in the storage 4 to search for map information corresponding to the request information, and reads out a searched result as a memory signal Sm. Then the element 1aprovides a designated terminal T with the memory signal Sm incorporated into the processing server signal Sc through the interface 5 and the Internet IN.

[0052] In response to the processing server signal Sc that composes request information, the route processing element 1buses the map information stored in the storage 4 so as to search for (compute) both of a route along which a vehicle runs and map information including the searched route. The element 1breads out a retrieved result as the memory signal Sm, and then provides a designated terminal T with the memory signal Sm, which is incorporated in the processing server signal Sc, via the interface 5 and the Internet IN.

[0053] In parallel with this processing, the route processing element 1bcreates route guide information needed to guide a vehicle with a specified terminal T along the retrieved route. The element 1bsupplies the terminal T with the created information in the form of the processing server signal Sc by way of the interface 5 and the Internet IN.

[0054] Further, on the basis of the request signal that has been received as the processing server signal Sc, the retrieving element 1csearches for the information, including spot information, stored in the storage 4 so that a searched result is read out as the memory signal Sm. The retrieving element 1cincorporates this memory signal Sm into the processing server signal Sc, which is then provided to a designated terminal T through the interface 5 and the Internet IN.

[0055] On the other hand, the input device 3 is placed to allow an operator to input necessary information into the CPU 1. On responding to such input processing, the input device 3 generates an input signal Sin indicative of such information-inputting processing, and provides the signal Sin to the CPU 1. The CPU 1 receives the input signal Sin and performs predetermined processing specified by the input signal Sin.

[0056] When the CPU 1 carries out processing specified by the input signal Sin, information which should be given an operator who operates the server SV is produced in the server SV. Such information that has been produced is handed over to the display 2 in the form of a display signal Sdp. Thus, the display 2 executes information given by the display signal Sdp.

[0057] Each terminal T has, as shown in FIG. 1C, a processor 10 serving as processing means, which includes a CPU and memories, a memory 11, a sensor 12 serving as a measurement member, a display 13, an audio output member 14, a transmitter/receiver 15 composed of for example a portable phone, and an input device 16.

[0058] Of these constituents, the transmitter/receiver 15 is responsible for two kinds of processing. That is, when the terminal signal St is received through the Internet IN, the transmitter/receiver 15 performs predetermined input-interface processing with the terminal signal St so as to produce a processing terminal signal Stt sent to the processor 10. Further, the transmitter/receiver 15 carries out predetermined output-interface processing with a processing terminal signal Stt that has been received from the processor 10, so that the terminal signal St is sent to the server SV through the Internet IN.

[0059] The sensor 12 is provided with, by way of example, a GPS (Global Positioning System) receiver, a speed sensor, and an acceleration sensor, though not shown in FIG. 1C. The GPS receiver receives a GPS electric wave that has been sent from GPS satellites travelling along their orbits. Because the GPS electric wave contains positional information, the sensor uses the positional information to compute information indicative of an absolute position of each vehicle on which each terminal T is mounted. The absolute positional information, which is expressed by both latitude and longitude information, is then sent from the sensor to the processor 10. The speed sensor is constructed in such a manner that it computes the mileage on each vehicle and speed thereof using a speed pulse signal coming from a not-shown pulse sensor to detect the rotation of a wheel of the vehicle, and outputs the computed mileage and speed information to the processor 10. Further, the acceleration sensor detects turn angles and slants in the up-and-down direction of each vehicle so as to output information representing the running direction of each vehicle to the processor 10. Thus, the above receiving and sensing elements allow the sensor 12 to provide the processor 10 with a sensor signal Ssc that corresponds to information in relation to a current position and an attitude of each vehicle and others.

[0060] The input device 16 of each terminal T is used by a crew to specify a desired map area to be displayed on the display 13, a desired destination, and others. This specification urges the navigation system to perform navigation processing in response to the specified information, so that the input device 16 produces an input signal Sin in which the specified information is reflected, and provides it to the processor 10.

[0061] The processor 10 operates on the received signals. That is, the processor 10 generates not only, based on the sensor signal Ssc, current positional information showing the current position of each vehicle on which each terminal T is mounted but also information about a request in which the input signal Sin is reflected. These pieces of information are transmitted, as the processing terminal information Stt, to the server SV via the transmitter/receiver 15.

[0062] The processor 10 receives the processing terminal signal Stt that has been transmitted from the server SV via the Internet IN and the transmitter/receiver 15. This processing terminal signal Stt indicates results that the server SV produces based on both the request information and the current positional information. Then the processor 10 extracts map information to be displayed from the processing terminal signal Stt and provides its extracted information to the display 13 as a display signal Sdp. The map information is displayed on the display 13. The information that will be displayed on the display 13 includes, in addition to the foregoing map information, map information along a route or route information according to route guide information, which are produced by the route processing element 1bof the server SV.

[0063] Of the route guide information, information which should be informed of a driver of each vehicle by a voice massage is outputted to the voice generator 14 as a voice signal Sad. This enables the voice generator 14 to utter a necessary voice message to guide the driver.

[0064] In addition, the map information and others which have been transmitted from the server SV, which are required to temporarily be stored, are sent from the processor 10 to the memory 11 in the form of a memory signal Sm for temporary storage therein. This memory signal Sm is read out, if required, for display or other purposes.

[0065] Referring to FIGS. 2 to 4, navigation processing carried out by the server SV of the foregoing navigation system S will now be described.

[0066] First, processing for retrieving a map (map retrieval processing) will be explained with the flowchart shown in FIG. 2. This processing is performed by the server SV in order to display a desired map on the display 13 of a designated terminal T.

[0067] When the CPU 1 starts the map retrieval processing, it is determined whether or not command information for a certain map has been received from each terminal T (step S1). If there has been no request information (No at step S1), the processing is continued with monitoring the reception of the request information. When such information has been received from a certain terminal T (Yes at step S1), the certain terminal T that has issued the request information is subjected to authentication processing which is carried out by the CPU 1 (step S2).

[0068] After the authentication processing has been completed, the CPU 1 (i.e., the retrieving element 1c) uses the received request information to retrieve map information from the storage 4. Namely, map information required by the map outputting element 1ais searched from all the pieces of map information stored by the storage 4 (steps S3, S4). When the retrieval is completed (Yes at step S4), the searched map information is transmitted to the certain terminal T through the interface 5 and the Internet IN (step S5).

[0069] During the transmission of the searched map information, it is monitored if or not all the pieces of information have been transmitted (step S6). When the monitoring shows that the transmission has not completed yet (No at step S6), the transmission is kept to continue. By contrast, when the transmission of all the pieces of necessary map information has been completed (Yes at step S6), the map retrieval processing is terminated.

[0070] Referring to FIG. 3A, route-calculating processing will now be described. This processing is prepared for calculating a route for guiding a vehicle on which the terminal T is mounted.

[0071] When this route-calculating processing is activated, the CPU 1 first checks whether or not information indicative of a request for route calculation has been received (step S20). Such request information includes a starting place, a destination place, and route conditions (for example, a preference is given to highways or a particular road is necessarily included) which are used to calculate a desired route by the CPU 1. This determination is continued until the reception of such request (No at step S20). On the other hand, in cases where such request for route calculation has been received from a certain terminal T (Yes at step S20), the certain terminal T that has issued the request is subjected to authentication processing which is carried out by the CPU 1 (step S21).

[0072] After the authentication processing, individual information about a user who owns the certain terminal T is extracted from the storage 4 (step S22). Then, based on both of various conditions, such as a destination place, included in the request information and the individual information acquired, the CPU 1 (i.e., the route processing element 1b) carries out route calculation processing in a predetermined manner (steps S23 and S24). On completing the route calculation processing (Yes at step S24), the calculated results are temporarily stored in a not-shown memory in the server SV, then the processing is ended. Another example may be configured such that the calculated results of requested route is transmitted to the certain terminal that issued the request to present it on the display 13 of the terminal T.

[0073] Referring to FIG. 3B, route-navigating processing will now be described, which is performed to guide, along the calculated route, a vehicle on which the above certain terminal T is mounted.

[0074] When this route-navigating processing is activated, the CPU 1 first checks whether or not information indicative of a request for starting a route guide has been received from the above certain terminal T (step S25). This determination is continued until the reception of such request (No at step S25). On the other hand, in cases where such request for a route guide has been received from the certain terminal T (Yes at step S25), the certain terminal T that has issued the request is subjected to authentication processing which is carried out by the CPU 1 (step S26).

[0075] After the completion of the authentication processing, individual information about a user who owns the certain terminal T is extracted from the storage 4 for confirmation (step S27). Then, in response to the request information, the CPU 1 (i.e., the route processing element 1b) carries out route-navigating processing necessary for navigation (step S28 and S29). The route-navigating processing is kept continuing until its completion is issued (step S29). Incidentally, the route-navigating processing carried out at step S28 includes processing for acquiring from the certain terminal T information indicative of the current position of the vehicle, processing for determining whether or not the current position is along the route calculated in advance, and processing for not only calculating geographical relationships between the vehicle's current position and well-known positional targets existing along a remaining part of the route along which the vehicle runs from now on but also transmitting the geographical relationships to the certain terminal T through the Internet TN for reference to the driver. The well-known positional targets are for example an intersection at which the vehicle should turn or a landmark toward which the vehicle should run.

[0076] Referring to FIG. 4, information retrieval processing carried out by each terminal T will now be described. This information retrieval processing is to retrieve information which should inform a driver on each terminal T and which relates to the navigation processing.

[0077] In this information retrieval information, first, it is checked whether or not a request for information to be informed has been transmitted from a certain terminal T (step S10). When such a request has not been received (No at step S10), the above checking process will be repeated. By contrast, in cases where it is determined that such a request has been issued from a certain terminal T (Yes at step S10), the processing is moved to authentication processing for the certain terminal T (step S11).

[0078] After completing the authentication processing, the request that has been transmitted is used by the CPU 1 (i.e., the retrieving element 1c) for retrieving necessary information form all the pieces of information stored in the storage 4 (steps S12 and S13). On completion of such information retrieval (Yes at step S13), the retrieved information is sent back to the certain terminal T through the Internet IN (step S14).

[0079] During the above transmission, it is then checked if all pieces of information to be transmitted to the certain terminal T has been transmitted or not (step S15). When there are left pieces of information to be transmitted from now on (No at step S15), the transmission processing is continued until the completion of transmission of all the pieces of information (Yes at step S15).

[0080] (II) Map data partially updateable

[0081] (Configuration)

[0082] As shown in FIG. 5A, a volume of map data M is stored in the storage 4 of the server SV. The map data M includes a group of data of layers L and data of a header H. The group of data of layers L is divided into a plurality of layers 1, 2, . . . , and each layer is further divided into a plurality of blocks B (1, 2, . . . ). Each block contains one or more objects O, thus being formed into a layered structure. That is, the first layer is composed of the layers L, the second layer is composed of the blocks B, and the third layer is composed of the objects O. For instance, as shown in FIG. 5A, the layer 1, which is one of the first layers L, is divided into plural blocks 1—1, 1-2, . . . , and one block 1—1 is further divided into plural objects 1—1—1, 1—1-2, . . .

[0083] In detail, as shown in FIG. 5B, each object O represents one road, one building, or others. The same type of objects O are collected to form each block B, thus, in the case of the road, providing a national road block, a principal district road block, or others. The blocks B are layered so that the highest-concept layers B, such as a road layer or a building layer, are provided.

[0084] Each layer L is constructed into an independent structure that is irrelevant to the other layers. Similarly, each block B is constructed into an independent structure that is irrelevant to the other blocks and each object O is constructed into an independent structure that is irrelevant to the other objects. Hence, in cases where one layer L is replaced, no effect is given to the other layers. The same is true of the blocks B and objects O. It is therefore possible to replace data, layer by layer, block by block, or object by object, by manipulating data only within or toward the storage 4. Thus, the storage 4 constitutes a computer-readable recording medium according to the present invention.

[0085] The header H shown in FIG. 5A contains the version of data, the version of a format, the type of data, a train of layer information, and a train of block information.

[0086] (Operations)

[0087] Referring to FIG. 6, a replacement of one layer will now be described.

[0088] In cases where a layer k in the current map data M1 is replaced, a new layer k′ is first prepared as a new set of data, as pictorially shown in FIG. 6. The current layer k is then replaced by the new layer k′, thereby providing an updated newest map data M2. The old layer k is different in a data size from the new layer k′. The replaced old data k is discarded.

[0089] Although not shown in FIG. 6, the same replacement as the above can be applied to the blocks B and the objects O, so that each block and each object can be replaced by new ones, block by block and object by object, respectively.

[0090] Referring to FIG. 7, a deletion and addition of a certain block will now be described.

[0091] In the case of the addition, as shown in FIG. 7, a new block x is first prepared, and then inserted into a location next to the block k in the current map data M1. In cases where a block l is deleted, a new block x is first prepared, the block x is inserted into a location next to the block k, and then discard the block l that should be deleted, thereby providing the newest updated map data M2. The above deletion and addition manners are true of the layers L and the objects O, so that the layers L and the objects O can be deleted or added every layer and every object, respectively.

[0092] In the present embodiment, when a certain layer L is deleted, it is required that all the corresponding blocks B to the certain layer L be deleted as well. When one or more layer L are added, it is needed to count the number of blocks existing in the map data so as to make information indicative of the number of layers. Additionally, when one or more blocks B are deleted or added, information indicative of the number of layers existing after the deletion or addition is renewed.

[0093] In the case that one or more objects O are deleted so as to make a certain block B vacant, layer information is renewed. Moreover, when an object O is added to the last of a certain block B, a terminator bit is updated.

[0094] (III) Update of delivered map data

[0095] Each terminal T has the memory 11 as shown in FIG. 1C. This memory 11 memorizes codes (unit codes) indicting blocks in a map and data dates (versions).

[0096] As shown in FIG. 8, when the server SV receives both the unit code and the data dates from a certain terminal T through the Internet IN, the server SV replies by sending back one or more sets each consisting of both of a data processing operand and primary data, to the certain terminal T through the Internet IN. Since there is a possibility that a plurality of such sets exist in the server, a terminator operand is used to detect the end of the data. In this detection, the way of previously defining the number of pieces of data may be adopted.

[0097] As to whether an update of map data is necessary or not, another modified configuration may be adopted. That is, when the unit codes (in general, a plural number) indicative of blocks in a map are transmitted to the server SV, a set of date codes (referred to as version codes) indicative of the versions are delivered successively to the server SV for the determination.

[0098] The header of data transmitted from the server SV is constructed based on a format shown in FIG. 9. In the header shown in FIG. 9, a data version is described using a production data (year, month and day) of map data, in which more than one up-versions per day will not be performed. A format version represents the number of format versions, and the type of data represents various categories of data with respect to a map. A series of bits of layer information, which are used to divide the map blocks into layers, is provided for each layer. A series of bits of block information are arranged in the order of depictions, and provided by an amount corresponding to a total number of blocks described by the layer information. In this layer information, the number of blocks belonging to each layer is described. Even when there is always no need for being divided into plural layers, a minimum of one layer is produced to satisfy the format. Adding all the numbers of blocks in the layer information provides the number of bits of block information.

[0099] After having received the unit codes and data dates from the certain terminal T through the Internet IN, if the server SV determines as shown in FIG. 8 that there is no need for an update of map data, the first operand becomes a terminator operand (operand is abbreviated as “OP”). In cases where the server SV determines that all the map data should be updated, the server SV is configured to transmit sets of both an all-data-update OP and all data to the certain designated terminal T via the Internet IN. Moreover, if the server SV determines that the map data should be updated in a partial manner, the server SV is configured to transmit, to the designated terminal T, sets of both a date-update OP and date data, and sets of both a data operation OP and primary data via the Internet IN. Accordingly, the server SV is able to update data in accordance with the operands in cases where the map data is partially updated, which allows only updated map data to be transmitted to the certain designated terminal T.

[0100] In cases where map data is partially replaceable for its update, update operations carried out by the server SV are based on a format shown in FIG. 10. Data processed on this format is delivered in a block-data structure at any time, in which data relevant to a data size is not stored.

[0101] In the satellite navigation system, it is frequent that data such as map data are required via a lower-speed communication line in which a mobile phone intervenes. In most cases, this data is not divided into packets. It is also probable that a vehicle (that is, a terminal T) is located outside a communicable range, which will not allow connections with the server SV even if a connection is required. In addition, the connection always involves a long period of time to authenticate a user, and this time for this authentication is relatively longer when taking vehicle's speeds into account.

[0102] In such a satellite communication system, it is therefore necessary for to acquire a mass of data at each of a plurality of positions and then turn off each connection. The various data are thus produced in the block-data structure to cope with the foregoing data acquisition carried out at each of the discontinuous locations.

[0103] The operations conducted on the format of FIG. 10 are directed to the primary data and include a replacement of deleting number-specified data and then inserting new data for the deleted data, a deletion of number-specified data, an insertion of new data before number-specified data, and an addition of new data after number-specified data.

[0104] Assigned data on the format shown in FIG. 10 show data to which the update operations are applied, and consist of dates, layers L, blocks B, and objects O. A data number size appearing in the foregoing format specifies the number of bytes in a field for the data number. The data number is specified by serial numbers. In the case that a plurality of updated data are applied to the same unit, the data number for the old data used before the update is specified. For each of the layers L, blocks B, and objects O, the data number starts from that of each of the top layer, the top block, and the top object.

[0105] Further, the primary data are present toward update operations other than the deleting operation. When the operations of deletion, insertion, and addition are performed, data present in other necessary locations are changed as well.

[0106] As a result, since the present embodiment adopts the data structure which is updateable partially, the update of map data can be realized such that only part of data, not the entire data, is transmitted to each terminal for the update thereat. It is thus possible to reduce an amount of data to be transmitted from the server SV to each terminal T, lightening a load on the communication line. This will lead to a lower cost in communication for the update as well as a shower time for the update.

[0107] Incidentally, the data to be transmitted to each terminal T for updating the map data thereat includes, in addition to map data, information showing operations required for the update. The update processing can be done in more complicated ways, such as entire data rewriting, partial data replacement, partial data deletion, and partial data addition.

[0108] Advantages

[0109] As a result, there are various advantages in the satellite navigation system of the present embodiment.

[0110] In detail, in the server SV, the map data can be updated partially, that is, every set of divided data map, in an easier manner. This partially updateable configuration is also effective in reloading map data from the server SV to each terminal T. For reloading the map data, it is sufficient that only one or more sets of map data that has been updated are delivered from the server SV to a certain terminal T. Hence an amount of map data to be downloaded can be reduced greatly.

[0111] Each terminal T is therefore able to update, set by set, map data temporarily stored for navigation by using both of only the received set of map data and the operation of a specified type. Therefore, for updating the map data used in each terminal T, a communicating load imposed on the Internet IN can be lessened noticeably, thus making the update faster and reducing a cost of the update.

[0112] Further, because the map data are divided into a plurality of sets independent of each other, each certain set of map data can be replaceable with no effect on the other sets of map data in terms of data connections. In addition, information indicating the type of an operation for update is transmitted to each terminal T together with updated map data. This transmission enables each navigating terminal to perform more complicated updating operations in an easier way.

[0113] Further, the layered structure of map data makes it easier to divide entire map data into a plurality of sets of map data classified according to their natures. By using the storage 4 (i.e, the recording medium), the server SV is able to provide a configuration in which map data for navigation can be updated partially.

[0114] It is enough for each terminal T to update the stored map data using only one or more received sets of map data. An amount of data involved in the update processing is reduced largely compared to the conventional. A load to calculate data by each terminal T diminishes as well, thus making the update faster and reducing a cost of the update.

[0115] The present invention is not limited to the above embodiment, but may be modified into various other forms. For example, the Internet IN adopted as the communication means in the above embodiment can be replaced by a communication network that uses a leased line or a public line.

[0116] Moreover, the terminal T can be composed of, other than the satellite navigation terminal like in the foregoing embodiment, a PDA (personal digital assistants), mobile phone, universal personal computer, various types of mobile terminals with communication interfaces, or home electronic devices with communication interfaces.

[0117] The present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The above embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the present invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

[0118] The entire disclosure of Japanese Patent Application No. 2001-232555 filed on Jul. 31, 2001 including the specification, claims, drawings and summary is incorporated herein by reference in its entirety.