Determination of accurate paddy field surface profile has great importance to designing the paddy tractor suspension system. With this aim, a new test rig has been designed and developed to measure paddy field surface profiles using static level method (sampled interval of 200mm). The data were analyzed through Matlab/Simulink software to obtain power spectral densities (0.05-3.5c/m) of the measured profiles on a log-log scale and it was found that the amplitude variation of the power spectral density (PSD) at low spatial frequency was higher than at high spatial frequency whereas the undulation of the PSD curve was largely changed from low to high frequency with roughness coefficient of 645.06x10-6 m3/cycle and slope value of 1.2399 representing the paddy field surface roughness under class D of ISO 8608 standards. This classification has great significance in the field of tractor vibration simulation work.
Keywords: Paddy field surface, Rod and Level, Static level method, ISO 8608.