机载LIDAR数据处理及其应用综述

机载LIDAR(Light Detection and Ranging)是一种无需任何或仅需少量的地面控制点的安装在飞机上的激光探测和测距系统,用于获得高精度、高密度的三维坐标数据,并构建目标物的三维立体模型。LIDAR具有自动化程度高、受天气影响小、数据生产周期短等特点,为获取高分辨率地球空间信息,可提供一种全新的技术手段。简单介绍机载LIDAR系统组成、特点、发展现状和趋势,详细阐述LIDAR数据处理的过程,并对现在存在的问题进行简单的论述,总结其应用领域,并对未来进行展望。     

基于LIDAR数据融合的数码城市三维重建

对三维激光扫描技术进行了简介,分析了目前数码城市三维重建的各种方法,指出其不足。提出利用机载LIDAR对一座城市进行三维空间数据采集,获取整座城市的LIDAR数据,按数码城市各部分建设的轻重缓急,分期分批地以地面LIDAR为补充获得更详实的数据,将二者所采集的数据进行融合,对3D数码城市三维重建进行探讨。     

基于虚拟三角网与坡度滤波的LIDAR点云数据滤波方法的研究

LIDAR(Light Detection and Ranging)技术由于其在数据获取和处理上的高度自动化,正广泛地被应用于各种地形数据的获取。LIDAR数据是目前最为理想的生产DEM的数据源,利用机载激光雷达获取DEM数据是机载激光雷达最为直接的应用。本文提出了一种将虚拟三角网与坡度滤波相结合处理LIDAR点云数据的方法,该方法将虚拟三角网的概念用于LIDAR滤波,避免了LIDAR点云内插或者平滑造成的信息损失。在虚拟三角网中进行初始地面点的选取,再由初始地面点生成的初始表面模型,通过坡度滤波可快速提取地面点。     

基于LIDAR点云数据插值方法研究

利用机载LIDAR技术可以获取高精度﹑高密度的三维坐标数据,并生成三维立体模型,构建用户感兴趣的DEM和DSM,如今需要快速高效的处理LIDAR点云数据,研究和探讨最合适的插值方法就显得特别重要,本文着重研究了不同插值算法的特点。     

LIDAR点云数据全自动滤波算法研究

提出了一种基于移动最小二乘法的点云数据全自动滤波算法,该方法首先对LIDAR点云数据进行合理分块,并建立分块网格的动态四叉树空间索引,便于数据操作和管理.对分块网格中的点云数据利用精简移动最小二乘法拟合出参考地形,将拟合得到的参考地形用于LIDAR点云高程阈值的迭代计算,将每次迭代前后高差小于阈值的点划为地面点,其余点划分为非地面点,迭代运算直至阈值满足要求为止.实验表明,精简移动二乘法效率高,计算量小,并且精度高,适合点云数据DEM(digital elevation model)拟合,利用该算法对LIDAR点云数据进行滤波的速度快、精度高,能够有效地识别地面点和非地面点,并保留地形的细节信息.     

三维地形信息测量系统的设计

在土地整理工作中,为降低工程土方量估算中三维地形信息测量的成本,同时提高测量精度与效率,设计了一种RTD DGPS与激光测量相结合的三维地形信息测量系统。使用RTD DGPS可以方便快捷地获得米级精度的水平位置数据;而高程的测量则采用激光测量系统完成,在100 m的范围内使用,其测量误差不大于4 cm,弥补了DGPS系统在高程测量中误差较大的不足。为满足野外作业的可靠性与便携性的需要,系统的数据采集部分以ARM7处理器为核心,并将采集的数据存储到U盘中。室外试验结果表明,系统工作稳定,可作为一种工具用于三维地形信息测量。     

LIDAR数据结合特征线获取高精度DEM及DOM

LIDAR点云数据是一种快速提取DEM的方法。但由于LIDAR点云的一些特性和地面上物体的复杂性,很难直接提取出高精度的DEM及获取高质量的DOM。介绍一种LIDAR点和特征线相结合的方式,即新兴技术和传统技术相结合,此方法既克服周期性长的缺点,又保证精度。     

机载激光雷达（LiDAR）技术及其应用

机载LiDAR技术是一种应用越来越广泛的新型测量系统,能够快速地获取高精度三维数据。过去十年,机载LiDAR技术作为精确、快速的地球表面三维测量方法已得到广泛认同。本文介绍了机载LiDAR技术的基本原理、数据处理流程及其应用。     

高效三维遥感信息获取技术的研究

分析了现有三维信息获取技术的现状.随着社会变化的快速需求,体现出了这种获取模式的最大弊端,即其时效性远远满足不了现代社会的应用需求.高分辨率卫星和机载激光扫描技术的出现恰恰弥补了这个不足,开辟了高效三维信息获取的新途径.高分辨率卫星影像不仅能提供具有丰富光谱信息的高质量影像,有的还直接提供DTM(Digital Terrain Model,数字地面模型)数据.激光扫描技术是获取地面三维信息的有效途径.实践表明,高效三维信息获取技术已在许多领域取得了较好的应用效果.     

机载毫米波InSAR测绘困难地区地形测图实践

干涉合成孔径雷达(Interferometric Synthetic Aperture Radar,InSAR)已成为获取高精度数字正射影像图(Digital Orthophoto Map,DOM)和数字表面模型(Digital Surface Model,DSM)的关键技术之一,其不受天气状况的影响,可以全天时、全天候进行数据获取.机载双天线毫米波In SAR不受失相关的影响,具有小体积、高分辨率、机动灵活等特点,可以实现大尺度、高精度成像.本研究利用机载双天线毫米波InSAR通过干涉批处理、区域网平差、地理编码、图像拼接镶嵌等步骤生成了贵州施秉试验区(丘陵、山地)和四川邛崃试验区(高山地)高精度的DOM与DSM,并利用地面控制点(GCPs,Ground Control Points)进行了精度验证,验证结果表明获取的DSM精度符合1∶5 000地形图绘制要求,表明了机载双天线毫米波InSAR具备生成不同地形的DOM/DSM的能力,为解决困难地区DOM/DSM数据缺失问题提供了新的技术手段.     

Effects of laser beam divergence angle on airborne LIDAR positioning errors

The influence of laser beam divergence angle on the positioning accuracy of scanning airborne light detection and ranging(LIDAR) is analyzed and simulated.Based on the data process and positioning principle of airborne LIDAR,the errors from pulse broadening induced by laser beam divergence angle are modeled and qualitatively analyzed for different terrain surfaces.Simulated results of positioning errors and suggestions to reduce them are given for the flat surface,the downhill of slope surface,and the uphill surface.     

Synchronous estimation of DTM and fractional vegetation cover in forested area from airborne LIDAR height and intensity data

We proposed a method to separate ground points and vegetation points from discrete return,small footprint airborne laser scanner data,called skewness change algorithm.The method,which makes use of intensity of laser scanner data,is especially applicable in steep,and forested areas.It does not take slope of forested area into account,while other algorithms consider the change of slope in steep forested area.The ground points and vegetation points can be used to estimate digital terrain model(DTM) and fractio...     

Synchronous estimation of DTM and fractional vegetation cover in forested area from airborne LIDAR height and intensity data

We proposed a method to separate ground points and vegetation points from discrete return, small footprint airborne laser scanner data, called skewness change algorithm. The method, which makes use of intensity of laser scanner data, is especially applicable in steep, and forested areas. It does not take slope of forested area into account, while other algorithms consider the change of slope in steep forested area. The ground points and vegetation points can be used to estimate digital terrain model (DTM) and fractional vegetation cover, respectively. A few vegetation points which were classified into the ground points were removed as noise before the generation of DTM. This method was tested in a test area of 10000 square meters. A LiteMapper-5600 laser system was used and a flight was carried out over a ground of 700–800 m. In this tested area, a total number of 1546 field measurement ground points were measured with a total station TOPCON GTS-602 and TOPCON GTS-7002 for validation of DTM and the mean error value is −18.5 cm and the RMSE (root mean square error) is ±20.9 cm. A data trap sizes of 4 m in diameter from airborne laser scanner data was selected to compute vegetation fraction cover. Validation of fractional vegetation cover was carried out using 15 hemispherical photographs, which are georeferenced to centimeter accuracy by differential GPS. The gap fraction was computed over a range of zenith angles 10° using the gap light analyzer (GLA) from each hemispherical photograph. The R ² for the regression of fractional vegetation cover from these ALS data and the respective field measurements is 0.7554. So this study presents a method for synchronous estimation of DTM and fractional vegetation cover in forested area from airborne LIDAR height and intensity data.

     

Synchronous estimation of DTM and fractional vegetation cover in forested area from airborne LIDAR height and intensity data

We proposed a method to separate ground points and vegetation points from discrete return, small footprint airborne laser scanner data, called skewness change algorithm. The method, which makes use of intensity of laser scanner data, is especially applicable in steep, and forested areas. It does not take slope of forested area into account, while other algorithms consider the change of slope in steep forested area. The ground points and vegetation points can be used to estimate digital terrain model (DTM) and fractional vegetation cover, respectively. A few vegetation points which were classified into the ground points were removed as noise before the generation of DTM. This method was tested in a test area of 10000 square meters. A LiteMapper-5600 laser system was used and a flight was carried out over a ground of 700–800 m. In this tested area, a total number of 1546 field measurement ground points were measured with a total station TOPCON GTS-602 and TOPCON GTS-7002 for validation of DTM and the mean error value is ?18.5 cm and the RMSE (root mean square error) is ±20.9 cm. A data trap sizes of 4 m in diameter from airborne laser scanner data was selected to compute vegetation fraction cover. Validation of fractional vegetation cover was carried out using 15 hemispherical photographs, which are georeferenced to centimeter accuracy by differential GPS. The gap fraction was computed over a range of zenith angles 10° using the gap light analyzer (GLA) from each hemispherical photograph. The R ² for the regression of fractional vegetation cover from these ALS data and the respective field measurements is 0.7554. So this study presents a method for synchronous estimation of DTM and fractional vegetation cover in forested area from airborne LIDAR height and intensity data.     

航空物探试验场地面地球物理场特征分析

航空地球物理探测技术是地质和矿产勘查的重要手段,其探测能力主要取决于测量系统及测量方法的有效性,而测量系统及测量方法有效性的提高,又需要专业的检验平台(航空物探试验场)。因此,在我国建立专业的航空物探试验场十分必要。本文搜集了我国某航空物探试验场的地质地球物理资料,在试验场设计并完成了重力、电阻率测深、瞬变电磁工作。通过对实测资料的处理和研究,将试验场划分为三个大的异常区,确定了试验场内的两个较大的断裂和一个次级断裂。本文在国内首次以专项工作的方式为航空重力及电磁法测量提供了高精度的参考数据,从而为国内航空地球物理测量系统检验和方法研究提供了综合平台。并且通过多种物探方法建立标准场的实践认识到,通过有效的选址,在充分利用已有的地质、地球物理(地面、航空)及测绘等资料的基础上,可以完善建成综合试验场,为航空物探飞行测量提供可靠的高精度对比资料。     

瑞利激光雷达探测中层大气密度和温度

利用瑞利（Rayleigh）散射激光雷达探测中层大气密度和温度的原理和方法,能够探测30~90 km范围的中层大气密度和温度的垂直分布。根据这种方法和实际测量得到的数据,把反演得到的结果与标准大气模型CI-RA86观测结果进行了对比,凸显具有较好的一致性。在一般情况下,30~65 km高度范围内激光雷达获得的大气密度与CIRA86密度偏差≤5%;温度偏差〈3 k,而在75 km以上温度偏差较大。     

利用激光雷达技术制作古建筑正射影像图

为了古建筑的数字化保护和修缮设计,利用激光雷达的方法制作古建筑正射影像图. 讨论了基本原理,论述了数据采集、三维三角网模型构建和正射影像图制作的过程和注意事项,最后制作了古建筑外立面的正射影像图.