Filtering errors when a rigid wheel is used to measure ground roughness

Measurement of ground roughness is needed for a very wide range of studies concerning vehicles traversing rough ground. Where a rolling wheel is used to follow a profile of rough ground during measurement there is the problem that short wavelength components of a profile may be attenuated, a wheel acting like a low-pass filter. Previous attempts to analyse the complete frequency response of a wheel filter have not been adequate to quantify the measurement errors it introduces. This paper presents a universal graph for estimating a cut-off wavelength of a wheel filter so enabling the probable effect of measurement errors to be judged. It is expected that, apart from ground roughness measurement, the graph will be used in metal surface measurement.