PROBLEM TO BE SOLVED: To provide a mechanism capable of performing automatic travel control without destroying a ridge planted with a crop.SOLUTION: An imaging section 110 images from an obliquely upper side an area of a crop land 200 containing a passage located between ridges planted with crops in a state in which an imaging direction is set in a travel direction of a work implement 100 and obtains an original image of the area. An image processing section 140 performs image processing of the original image obtained by the imaging section 110 and thereby calculates an angle of the work implement 100 in the travel direction with respect to the ridge and a position deviation amount from a center position of the ridge in the work implement 100.SELECTED DRAWING: Figure 2
