In order to reduce velocity measurement error,a novel laser Doppler velocimeter(LDV) based on Janus configuration is presented.The variation of the inclination angle was calculated by two detected Doppler frequencies and the inclination angle,and then the measured velocity of the vehicle was compensated.The results of the theory and experiments show that the LDV based on Janus configuration is insensitive to the inclination angle,and its measurement accuracy is better than that of conventional reference-bea...