In this research, the automatic level measurement system used in leveling for direct planting of rice is developed. A laser transmitter and a receiver are used as measuring equipments. The method for automatic level measurement is devised and the problem of level measurement on irregular land surface is discussed. This problem, inclination error can be compensated by attaching rotating mass. Using dynamic equations of this system, the value of design variables are determined.
The level measuring experiment is performed about three level change shapes. This system can measure step shape level change of which amplitude is 40mm in 0.8sec, random shape level change within ±5mm(maximun measurement error) and sine shape level change of which spatial frequency is $0.5m^{-1}$ accurately. To verify performance of the inclination error compensation system, frequency transfer function(acceleration input vs. inclination error) is computed by spectural analysis. The Inclination error is decreased about 20dB by error compensation system.
