The Evaluation of Close-range Photogrammetry for the Modelling of Mouldboard Plough Surfaces

The geometric heterogeneity existing in mouldboard ploughs hinders its inclusion in models in which the redistribution of soil particles is predicted, or the force exerted on the working component is measured. In this study, both the mathematical surface (second-, third- and fourth-order polynomials, both splines and Bezier) and the number of control points required for its adjustment (100, 49, 25, 20, 16), are examined to produce optimal modelling of the mouldboard plough geometry. The three-dimensional coordinates of 193 points on the surface of a plough are measured with great accuracy (root mean square 0·66 mm), using low-cost close-range photogrammetry. The results obtained indicate that the surface of a mouldboard plough can be shaped with an accuracy of approximately 1·30 mm, with the adjustment of a cubic polynomial surface to just 25 control points randomly distributed over the surface of the plough.