Large-picture detection method

The invention relates to the technical field of detection, and particularly relates to a large-picture detection method. The large-picture detection method comprises the steps of providing a grid, wherein the grid is placed in a coordinate system, placing a detected object in the grid, and acquiring images of the object and the grid together by an image acquiring device; transmitting the acquired images to a computer so as to be analyzed and processed, acquiring a contour trace of the detected object, and converting coordinates of a detected point through measuring the distance between the detected point on the contour trace and a nearby grid line. The large-picture detection method does not need to find the center of a lens, the coordinates of the detected point are converted through measuring the distance between the detected point and the nearby grid line, a measurement area is fragmented, the detected point is basically consistent with the nearby grid line in bending deformation, and an error brought about by image bending deformation is effectively reduced. Coordinates of the grid line are fixed values in the coordinate system, and high-precision contour trace coordinates of the detected objected are acquired through conversion processing of the computer. Therefore, the large-picture detection method is convenient and efficient in large-picture detection, and the detection precision is high.