Fig. 12. Asymmetry in weights of healthy cow (ID: 55) and lame cow (ID: 123). Detecting Lameness from Hoof Landing Positions With the onset of hoof disease and lameness, certain spatial parameters such as the stride length of the cow start to change. Stride length is the distance between two consecutive imprints of the same hoof, as shown in Fig. 13. The stride length measurements are passed to the inference engine which evaluates the change over time to infer if lameness has set in. A snapshot of stride length measurement of the healthy cow (ID: 55) and the lame cow (ID: 123) are shown in Fig. 14. Lameness results in the movement of a limb away from the midline of the body. Hence, another useful spatial parameter for the inference engine is the abduction. It is the sideways distance between the front hoof and the hind hoof on the same side. An example is shown in Fig. 15. The abduction is calculated for the left side, the right side and as an average. Asymmetry in the left and right abduction indicates uneven swaying of the body weight during walking. Fig. 16 shows the abduction measurements for the healthy cow (ID: 55) and the lame cow (ID: 123). Using the four-segment platform, the abduction is measured twice for each side for every walk of the cow over the platform. Large scale testing showed average abduction has strong significance, indicating that a lame cow tends to walk with her back legs slightly further apart. A healthy cow's hind leg would be an average of 20 mm outside of the front hoof placement, compared to 30 mm for a lame cow's leg. Although 10 mm does not seem like much Fig. 13. Example of a stride length measurement. Fig. 14. Stride lengths for a healthy cow (ID: 55) and lame cow (ID: 123). Fig. 15. Example of abduction (right side). September 2020 IEEE Instrumentation & Measurement Magazine 39