Abstract: A ground contact height sensor for a harvesting header comprises a transverse rotatable shaft, a first rigid arm, a second rigid arm and a connecting member. The rotatable shaft is rotatively mounted to the frame of the header. The first rigid arm is rigidly mounted to the rotatable shaft. The first arm extends downwardly and rearwardly from the rotatable shaft in a curved manner. The second rigid arm is pivotally coupled to the first rigid arm by a hinge joint. The second rigid arm extends upwardly and rearwardly from the second end of the first rigid arm. The first and second rigid arms defining a relatively large radius. The connecting member secures the rearmost end of the second rigid arm to the frame of the header. To maintain the radius of the two pivotally connected rigid arms the hinge joint joining the two rigid arms is provided with a torsion spring.