针对现有直升机机载光电稳瞄系统高精度角度测量和角速率测量的特点，提出一种利用测量目标相对角度和角度变化率等参数实现目标实时被动测距的方法。建立了机载稳瞄平台对地面固定目标定位的数学模型，提出利用系统旋转变压器测量目标角度，利用惯性速率陀螺测量目标角度变化率。该方法使得目标角度变化率的测量精度(优于0.1mrad/s)比一般光学方法提高了一个数量级。利用扩展卡耳曼滤波(EKF)算法提高目标距离估算精度，保证测量结果的稳定性。理论仿真和外场验证实验结果表明，该方法可以实时估算目标相对载机的距离，适合于武装直升机快速实时目标定位。

Since the angle and angular rate measurement of the existing helicopter-borne stabilized sight system is very accurate, a real-time target passive ranging method is put forward based on these measurements. The mathematical model for locating fixed ground target by helicopter-borne stabilized sight system was established, a rotary variable differential transformer was used to measure target angle and an inertial gyroscope was used to measure target angle variation rate. The measurement accuracy is better than 0.1mrad/s, which is ten times accurate than before. The stability and precision of ranging measurement system are improved by extend Kalman filter (EKF). The simulation and experiment results indicate, it can make real-time target range estimation, which is suitable for the real time target position of attack helicopter.