Analysis of performance and study of data acquirement in airborne laser bathymetry

机载激光测深雷达是利用机载的蓝绿激光发射和接收设备，通过发射大功率窄脉冲激光，探测海洋水深三维地理信息的一种先进的、主动遥测系统。它具有很高的效率和探测点密度，强机动性，低运行成本以及操作简便等许多优点。本论文是国家863高技术计划机载激光测深系统专项课题的研究内容，该课题将研制一套机载、高空间分辨率、高精度浅海海底立体探测系统。本论文重点研究该系统的实时数据采集系统及相关理论问题分析。论文首先对机载激光测深系统进行系统的阐述，详细分析了当前发展概况；接着在第二部分详细讨论与机载海洋激光测深系统最大测量深度相关的各因子之间的关系，并利用最小可探测信噪比为判据，对机载海洋激光测深系统在白天和晚上工作进行了数值模拟，通过比较最大测量深度与激光脉冲峰值功率、接收视场角、接收口径和光谱接收带宽等关系，来确定系统的主要参量数值，使系统具有白天49m和晚上65m的最大测量深度同时介绍了测深精度相关问题。第二部分还针对椭圆形（圆形）扫描方式来分析激光测深雷达的水平分辨力特性和其变化规律，通过考察码盘转速、激光脉冲重复频率、飞机航高以及飞机航速等因素对水平分辨力的影响，找出改善激光测深雷达系统水平分辨力的最佳途径，使得系统具有sxsm的空间分辨力。作为论文的另一个重要组成部分，设计和研制了一套大数据量、高中断频率的机载激光测深雷达的实时数据采集系统。论文根据数据系统的硬件组成，时序关系，同步关系，设计了一套高速、实时的数据采集软件系统；该系统基于用户友好的Willdows98操作系统，利用硬件中断方式，成功实现中断频率为100OHz的多路数据采集，能以约为16Mb／s的速率实时接收并存储到计算机硬盘中。软件成功通过了测试，可以满足机载激光测深系统的要求。Airborne laser bathymetry (ALB) is a kind of system to measure sea depth using airborne laser transiver. It's an advanced technique with many virtues such as high spatial resolution, excellent flexibility, low cost and easier operation. This thesis is mainly emphasized on the studies of real-time data acquirement system design and the performance evaluation in ALB. It is also one part of works in the 863 project of airborne laser depth mapping. At first, histroy, principle and developing status of ALB are generally overviewed. The performance of ALB is discussed and evaluated in the second chapter of this thesis. The relationship between parameters of ALB and its maximum penetration depth is discussed; The minimum ratio of signal to noise is taken as the criteria of choosing parameter; The relationships between maximum penetration depth, transmitted peak power, receiver area, field of view, and spectral bandwidth of filter are demonstrated. Results showed that ALB system with the chosen parameters has a penetrability of 49m in daytime and 65m in nighttime. In addational, some factors which affecting the accuracy of depth are discussed. The scanning pattern, spatial resolution are also analysed with the different scanner speed, the repetition rate of laser, the altitude and speed of aircraft. Results show that the system can gain a spatial resolution as small as 5 * 5m. As another main work in this thesis, a high interrupt-frequency and high volume data real-time acquirement system of ALB is designed. Based on the information of hardare devices, the signal sequence and synchronization relationship in system, a high speed and real-time software is developed. This software system successes in muti-channel data acquirement with 1000Hz and the hard disk saving rate of 16Mb/s by hardware interrupting under Winows98 OS. the software is tested successfully, which can fulfil the desire of ALB system