Data communication device, data communication system, and recording medium

A data communication system in which a data communication device communicates data with a server, comprising:

• the data communication device, capable of being mounted on a vehicle, including:
• a first memory storing road map information indicating locations of a plurality of nodes assigned with numbers in a road network that is represented by the nodes and a plurality of links each connecting two adjacent ones of the nodes,
• a second memory storing a time when the vehicle enters a link, and identification data about the link,
• a third memory storing a location of the vehicle at a certain time, and identification data about the link corresponding to the location,
• a position measuring unit periodically acquiring position data indicating a location of the vehicle,
• a determining unit identifying a link corresponding to an acquired latest position data based on the road map information every time position data is acquired, and comparing the identified link with the link stored in the third memory to determine whether the vehicle has passed through a node,
• a first updating unit receiving a determination result indicating that the vehicle has not passed through a node, and rewriting the position data and acquired time stored in the third memory to the last acquired position data and acquired time,
• a calculating unit receiving a determination result indicating that the vehicle has passed through a node, determining the latest exit time based on the acquired time stored in the third memory and the time when the position measuring unit has last acquired position data, and calculating a travel period indicating a time required for the vehicle to pass through the link from which the vehicle has last exited, based on the determined exit time and the entry time stored in the second memory,
• a second updating unit writing the exit time last determined by the calculating unit as an entry time in place of the entry time stored in the second memory after the end of the travel period calculation, and rewriting the link identification data stored in the second memory to the identification data about the link last identified by the determining unit, and
• a transmitting unit transmitting the calculated travel period and the identification data about the corresponding link to the server;
• and
• the server including:
• a receiving unit receiving the calculated travel period and the identification data.

A computer-readable recording medium storing a computer program for causing a computer to function as a data communication device capable of being mounted on a vehicle via a wireless network, the computer program causing the computer to execute an operation comprising:

• periodically acquiring position data indicating a location of the vehicle;
• identifying a link corresponding to an acquired latest position data based on road map information every time position data is acquired, and comparing the identified link with a link stored to determine whether the vehicle has passed through a node, the road map information indicating a location of each of a plurality of nodes in a road network that is represented by the nodes assigned with numbers stored and a plurality of links connecting each two adjacent ones of the nodes;
• executing a first rewriting of the position data and acquired time stored in the third memory to the last acquired position data and acquired time, upon receipt of a determination result indicating that the vehicle has not passed through a node;
• determining, upon receipt of a determination result indicating that the vehicle has passed through a node, the latest exit time based on the acquired time stored in the third memory and the time when the acquiring of the position data has last acquired position data, and calculating a travel period indicating a time required for the vehicle to pass through the link from which the vehicle has last exited, based on the determined exit time and an entry time stored in a second memory;
• executing a second writing of the exit time last determined through the calculating as an entry time in place of the entry time stored in the second memory after the end of the travel period calculation, and rewriting link identification data stored in the second memory to identification data about the link last identified through the acquiring;
• and
• transmitting the calculated travel period and the identification data about the corresponding link to a given communication destination.

An information gathering method for gathering information from a data communication device capable of being mounted on a vehicle in a traffic information providing system, the information being gathered by a server in the traffic information providing system, the method causing the data communication device to execute an operation, comprising:

• storing road map information in a first memory, the road map information indicating locations of a plurality of nodes assigned with numbers in a road network that is represented by the nodes and a plurality of links each connecting two adjacent ones of the nodes;
• storing a time when the vehicle enters a link, and identification data about the link in a second memory;
• storing a location of the vehicle at a certain time, and identification data about the link corresponding to the location in a third memory,
• the data communication device carrying out an operation including:
• periodically acquiring position data indicating a location of the vehicle;
• identifying a link corresponding to an acquired latest position data based on the road map information every time position data is acquired, and comparing the identified link with the link stored in the third memory to determine whether the vehicle has passed through a node;
• updating the position data and acquired time stored in the third memory to the last acquired position data and acquired time, when the vehicle has not passed through the node;
• determining the latest exit time based on the acquired time stored in the third memory and the time when the position measuring unit has last acquired position data, and calculating a travel period indicating a time required for the vehicle to pass through the link from which the vehicle has last exited, based on the determined exit time and the entry time stored in the second memory, when the vehicle has passed through the node;
• writing the last determined exit time as an entry time in place of the entry time stored in the second memory after the end of the travel period calculation, and rewriting the link identification data stored in the second memory to the identification data about the last identified link;
• and
• transmitting the calculated travel period and the identification data about the corresponding link to the server.