Claims [Claim 1] A vehicle determination apparatus comprising:
a direction identification unit to identify a traveling direction in which a surrounding vehicle travels in a partial region of a region indicated by image information obtained by photographing by a camera;
a feature amount acquisition unit to acquire a reference feature amount being a feature amount computed from a reference image corresponding to the traveling direction identified by the direction identification unit; and
a vehicle determination unit to compute an image feature amount being a feature amount of the image information of the partial region and compare the computed image feature amount with the reference feature amount acquired by the feature amount acquisition unit, thereby determining whether or not the surrounding vehicle is present in the partial region. [Claim 2] The vehicle determination apparatus according to claim 1,
wherein the direction identification unit identifies the traveling direction, based on a position of the partial region in the region indicated by the image information. [Claim 3] The vehicle determination apparatus according to claim 2,
wherein the direction identification unit identifies the traveling direction, based on a position of a partial region in which a surrounding vehicle was determined to be present by the vehicle determination unit in the past. [Claim 4] The vehicle determination apparatus according to claim 2, further comprising:
a lane identification unit to identify a travel lane in which a vehicle with the camera mounted thereon travels,
wherein the direction identification unit identifies the traveling direction,

based on the travel lane identified by the lane identification unit. [Claim 5] The vehicle identification apparatus according to claim 2,
wherein the direction identification unit identifies a region of a parallel lane with a same traveling direction as a traveling direction of a vehicle with the camera mounted thereon and a region of an opposite lane with a traveling direction opposite to the traveling direction of the vehicle with the camera mounted thereon, thereby identifying the traveling direction. [Claim 6] The vehicle determination apparatus according to claim 1, further comprising:
a lane identification unit to identify a travel lane in which a vehicle with the camera mounted thereon travels and an associated lane associated with the partial region,
wherein the feature amount acquisition unit acquires the reference feature amount computed from a reference image corresponding to a relative position of the associated lane with respect to the travel lane identified by the lane identification unit. [Claim 7] The vehicle determination apparatus according to claim 6,
wherein the feature amount acquisition unit acquires the reference feature amount computed from a reference image corresponding to a position of the partial region in an upper or a lower direction of the region indicated by the image information. [Claim 8] The vehicle determination apparatus according to claim 1, further comprising:
a shielding determination unit to determine whether or not the partial region is a region including a shielded region overlapping with a different partial region determined by the vehicle determination unit that a surrounding vehicle was present,
wherein the feature amount acquisition unit acquires the reference feature amount computed using a reference image corresponding to whether or not the partial region has been determined to be the region including the shielded region by the

shielding determination unit.
[Claim 9] A vehicle determination method comprising:
identifying a traveling direction in which a surrounding vehicle travels in a partial region of a region indicated by image information obtained by photographing by a camera;
acquiring a reference feature amount being a feature amount computed from a reference image corresponding to the identified traveling direction; and
computing an image feature amount being a feature amount of the image information of the partial region and comparing the computed image feature amount with the acquired reference feature amount, thereby determining whether or not the surrounding vehicle is present in the partial region. [Claim 10] A vehicle determination program to cause a computer to execute:
a direction identification process of identifying a traveling direction in which a surrounding vehicle travels in a partial region of a region indicated by image information obtained by photographing by a camera;
a feature amount acquisition process of acquiring a reference feature amount being a feature amount computed from a reference image corresponding to the traveling direction identified by the direction identification process; and
a vehicle determination process of computing an image feature amount being a feature amount of the image information of the partial region and comparing the computed image feature amount with the reference feature amount acquired by the feature amount acquisition process, thereby determining whether or not the surrounding vehicle is present in the partial region.