The factors include ultrasonic wave frequence , condition temperature , ultrasonic converter instrinisic system error , hareware extended time , electricity noise and sonic noise in the spot , city power defmcient pressure and exceeded pressure , city power peak and pour . we adopt the following compensation schemes of error in the system . about ultrasonic wave frequence ' s effect to measurement precision , we can choose appropriate frequence according to the measured distance 在空气和液压缸中影响测距精度的主要因素包括：超声波的频率、环境温度、超声换能器本身的系统误差(即探头固定误差) 、硬件时间延迟、工作现场的电噪声和声噪声、市电的过压、介压噪声以及市电的尖峰和浪涌噪声，在本系统中采取了以下几种误差的补偿方案： ?对于超声波的频率对测量精度的影响，只能根据测距的距离选择合适的超声频率。
The fairly well imaging results indicate that the range - doppler algorithm is effective on the condition of side - looking withoat squillt . after that , we discussed some sources of motion errors and introduced the influence of phase errors to imaging , and came to an conclusion that phase errors is one of the dominating reasons decreasing imaging quality in this dissertation , the experiments of point target imaging were done to explain the problem aroused by quadratic and cubic phase errors influent the imaging . in order to effectively eliminate or reduce the influence of motion ermrs to imaging , thiee representative autofocus a1gorithjns were discussed , i . e . map drift , shift and correlation , phase gradient autofocus 本论文就是以研究运动误差补偿为目的，首先分析了合成孔径雷达的基本原理及其成像原理，应用距离一多普勒（ r d ）成像算法对机载l波段sar实际数据进行了成像，表明r d算法对正侧视的sar数据成像是有效的；然后研究了由运动误差引起的相位误差对成像的影响，得到的结论是：回波数据中的相位误差是导致雷达图象质量下降的主要原因之一；重点针对二阶相位误差的补偿问题，研究了三种具有代表性的自动聚焦算法，用点目标实现了仿真并对实际数据进行了自动聚焦处理，经过自动聚焦前后结果的比较和分析，可以看出：子孔径相关法（ mapnrift ）对二次相位误差估计比较精确、移频相关法侣hiftandcorrelation ）对数据处理速度快、而相位梯度法（ phas 。
