Distance image outputted from an image processor is read by a recognition/judgment
computer, in which the distance image is divided into strips having a specified
interval and a histogram is prepared for each strip. Based on the histogram, the
position of solid objects and the distance thereto are obtained and these positional
data of the solid objects are classified into groups of solid object and groups
of side wall. Further, the position of a wall surface forming a boundary of a road
is detected from the data of the groups of side wall. On the other hand, assuming
a wall surface model composed of a series of nodes, respective nodes are determined
and corrected by the data of side wall. Thus obtained nodes form a successive wall
surface along a curved road.
