Claims [Claim 1] A driving support apparatus comprising:
a map generation unit to generate a first map being a three-dimensional map indicating three-dimensional positions of objects around a vehicle;
a coordinate synchronization unit to convert at least one of the first map generated by the map generation unit and a second map so that the first map and the second map become three-dimensional maps in a same coordinate system, the second map being a three-dimensional map indicating three-dimensional positions of objects around an external apparatus, the external apparatus being one of a roadside apparatus and a different vehicle from the vehicle; and
a synthesizing unit to generate a composite map by synthesizing the first map and the second map after the conversion by the coordinate synchronization unit. [Claim 2] The driving support system according to claim 1,
wherein the coordinate synchronization unit converts the second map so that a second coordinate system being a coordinate system of the second map matches a first coordinate system being a coordinate system of the first map. [Claim 3] The driving support apparatus according to claim 2,
wherein the coordinate synchronization unit includes:
a target point extraction unit to repeatedly extract, from a plurality of points indicating the three-dimensional positions of the objects in the first map, three target points, as a point al, a point a2, and a point a3 and to repeatedly extract, from a plurality of points indicating the three-dimensional positions of the objects in the second map, three target points respectively made to correspond to the point al, the point a2, and the point a3, as a point bl, a point b2, and a point b3;
a likelihood computation unit to compute a likelihood when the point al and

the point bl indicate a same position, the point a2 and the point b2 indicate a same position, and the point a3 and the point b3 indicate a same position;
a conversion amount computation unit to compute a conversion amount for matching the second coordinate system to the first coordinate system, assuming that, with respect to the target points repeatedly extracted by the target point extraction unit and having a high likelihood computed by the likelihood computation unit, the point al and the point bl indicate the same position, the point a2 and the point b2 indicate the same position, and the point a3 and the point b3 indicate the same position; and
a coordinate conversion unit to convert the second map, using the conversion amount computed by the conversion amount computation unit. [Claim 4] The driving support apparatus according to claim 3,
wherein the likelihood computation unit includes:
a second point position computation unit to compute, using a distance between the point bl and the point b2, the position of the point b2 when the point bl is placed at the same position as the point al in the first coordinate system and the point b2 is placed on a straight line X passing through the point al and the point a2;
a third point position computation unit to compute, using a distance between the point b2 and the point b3, the position of the point b3 when the point b3 is placed on a straight line Z in the first coordinate system, the straight line Z being obtained by moving a straight line Y passing through the point a2 and the point a3 in parallel so that the straight line Y passes through the position of the point b2 computed by the second point position computation unit; and
an inter-third-point distance computation unit to compute a distance between the point a3 and the position of the point b3 computed by the third point position computation unit, as the likelihood.

[Claim 5] The driving support apparatus according to claim 3,
wherein the likelihood computation unit includes:
a rotation computation unit to compute a rotation amount when a straight line Y passing through the point bl and the point b2 in the second coordinate system is converted to a straight line parallel to a straight line X passing through the point al and the point a2 in the first coordinate system;
a translation amount computation unit to compute a translation amount in the conversion amount when a rotation amount in the conversion amount for matching the second coordinate system to the first coordinate system is assumed to be the rotation amount computed by the rotation computation unit;
a converted position computation unit to compute the positions of the point bl, the point b2, and the point b3 in the first coordinate system, based on the rotation amount computed by the rotation computation unit and the translation amount computed by the translation amount computation unit; and
a distance computation unit to compute a sum of a distance between the point al and the position of the point bl computed by the converted position computation unit, a distance between the point a2 and the position of the b2 computed by the converted position computation unit, and a distance between the point a3 and the position of the point b3 computed by the converted position computation unit, as the likelihood. [Claim 6] The driving support apparatus according to claim 3,
wherein the likelihood computation unit includes:
an inter-point distance computation unit to compute a distance al2 between the point al and the point a2, a distance a23 between the point a2 and the point a3, a distance al3 between the point al and the point a3, a distance bl2 between the point bl and the point b2, a distance b23 between the point b2 and the point b3, and a distance

bl3 between the point bl and the point b3; and
a difference computation unit to compute a sum of a difference between the distance al2 and the distance bl2, a difference between the distance a23 and the distance b23, and a difference between the distance al3 and the distance M3, as the likelihood. [Claim 7] The driving support apparatus according to claim 3,
wherein the target point extraction unit extracts, as the point bl, a point indicating the position of the object having an attribute being the same as an attribute of the object whose position is indicated by the point al, extracts, as the point b2, a point indicating the position of the object having an attribute being the same as an attribute of the object whose position is indicated by the point a2, and extracts, as the point b3, a point indicating the position of the object having an attribute being the same as an attribute of the object whose position is indicated by the point a3. [Claim 8] The driving support apparatus according to claim 1,
wherein the coordinate synchronization unit converts the first map so that a first coordinate system being a coordinate system of the first map matches a third coordinate system, and converts the second map so that a second coordinate system being a coordinate system of the second map matches the third coordinate system, the third coordinate system being different from the first coordinate system and the second coordinate system. [Claim 9] The driving support apparatus according to claim 1, further comprising:
a receiving unit to receive a plurality of the second maps from an externally mounted apparatus mounted on the external apparatus; and
a time synchronization unit to identify, among the plurality of the second maps received by the receiving unit, the second map generated from data acquired at a

same time as an acquisition time of data used for generating the first map,
wherein the synthesizing unit synthesizes the first map and the second map identified by the time synchronization unit. [Claim 10] The driving support apparatus according to claim 9,
wherein when there is not the second map generated from the data acquired at the same time as the acquisition time, the time synchronization unit estimates the second map to be generated from the data acquired at the same time as the acquisition time, using the plurality of the second maps, and
wherein the synthesizing unit synthesizes the first map and the second map estimated by the time synchronization unit. [Claim 11] The driving support apparatus according to claim 1, further comprising:
a route determination unit to determine a travel route, based on the composite map generated by the synthesizing unit; and
a vehicle control unit to control the vehicle so that the vehicle travels on the travel route determined by the route determination unit. [Claim 12] The driving support apparatus according to claim 1, further comprising:
a display unit to display the composite map generated by the synthesizing unit.
[Claim 13] A driving support system comprising a driving support apparatus installed on a vehicle and an externally mounted apparatus mounted on an external apparatus being one of a roadside apparatus and a different vehicle from the vehicle,
wherein the externally mounted apparatus includes:
a transmitting unit to transmit data regarding positions of objects around the external apparatus to the driving support apparatus, and
wherein the driving support apparatus includes:

a map generation unit to generate a first map being a three-dimensional map indicating three-dimensional positions of objects around the vehicle;
a receiving unit to receive the data regarding the positions transmitted by the transmission unit;
a coordinate synchronization unit to convert at least one of the first map generated by the map generation unit and a second map obtained from the data regarding the positions received by the receiving unit so that first map and the second map become three-dimensional maps in a same coordinate system; and
a synthesizing unit to generate a composite map by synthesizing the first map and the second map after the conversion of a coordinate system by the coordinate synchronization unit. [Claim 14] A driving support method comprising:
generating a first map being a three-dimensional map indicating three-dimensional positions of objects around a vehicle;
converting at least one of the first map and a second map being a three-dimensional map indicating three-dimensional positions of objects around an external apparatus so that first map and the second map become three-dimensional maps in a same coordinate system, the external apparatus being one of a roadside apparatus and a different vehicle from the vehicle; and
generating a composite map by synthesizing the first map and the second map after the conversion. [Claim 15] A driving support program to cause a computer to execute:
a map generation process of generating a first map being a three-dimensional map indicating three-dimensional positions of objects around a vehicle;
a coordinate synchronization process of converting at least one of the first

map generated by the map generation process and a second map being a three-dimensional map indicating three-dimensional positions of objects around an external apparatus so that first map and the second map become three-dimensional maps in a same coordinate system, the external apparatus being one of a roadside apparatus and a different vehicle from the vehicle; and
a synthesis process of generating a composite map by synthesizing the first map and the second map after the conversion by the coordinate synchronization process.