大比例尺DEM关键技术指标的探讨

DEM是基础地理信息数字产品的重要组成部分。通过分析国外大比例尺DEM的技术指标,了解和研究国内大比例尺DEM的需求和生产状况,以及当前新技术的发展现状,探讨了基于规则格网的大比例尺DEM的关键技术指标,并分析其与相应比例尺地形图等高线表示高程精度的关系,提出了合理的大比例尺DEM格网间距和高程精度要求,以推进大比例尺DEM成果的标准化和规范化。     

基于地形图的大比例尺DEM精度检查技术

大比例尺DEM成果精度检查是数据质量检查的核心内容,如何全面核查DEM成果精度、快速发现粗差区域对于指导DEM数据生产、提高成果质量有重要意义。结合武汉市大比例尺DEM数据生产及检查工作现状,提出以全要素地形图为基础,采用基于FME的高程信息提取模型和DEM精度检查模型,通过ArcGIS模板和Python自动化处理脚本对DEM成果精度进行检查分析和统计的处理技术。试验结果表明,该方法能提高DEM成果精度检查分析的效率和质量,可广泛应用于DEM数据生产实践。     

无人机影像数据提取大比例尺DEM的方法研究

以新疆某个试验测区为例,介绍了利用Pix4DMapper全自动摄影测量软件结合Terrasolid LDAR点云数据处理软件提取高精度DEM的方法与基本流程。通过实测的路面高程点与获取的DEM高程值做对比进行精度评价,试验结果表明,通过差分GPS无人机影像数据提取的DEM,可满足1∶2 000大比例尺地形图平坦地区DEM的精度要求。     

基于小波多尺度分析的DEM数据综合研究

在同一地区,随着数字高程模型(DEM)分辨率的降低,或者地形图比例尺的缩小,DEM或地形图所描述的地形表面的细节部分不断舍弃而表现出宏观的骨架特征。本文将小波多尺度分析方法和方根模型结合模拟这一过程,由基于1:1万比例尺地形图建立的DEM生成了两种新的较小比例尺DEM,对比不同比例尺等高线可知,较小比例尺保持了较大比例尺的山体轮廓、山脊、谷地走向等地貌形态的塑造。采用坡度和剖面曲率两个参数及信息论的方法,分别对原始DEM和新生成的DEM进行分析和验证,结果表明,DEM经过数据综合,不但地形表面的轮廓越来越平缓,而且地形表面的细节也越来越平滑。利用方根模型作为小波高频系数阈值选取的依据更贴近于传统制图综合方法,能够将比例尺的改变与综合程度结合起来,实现任意比例尺DEM的自动综合。     

DEM数据高程精化方法研究

由于采用不同技术规程规范的原因,目前1∶500比例尺DEM数据高程中误差往往跟1∶500比例尺地形图高程中误差约相差5 cm,为了基础测绘数据的融合和精度统一,笔者在浙江省台州市椒江试验区对DEM数据进行高程精度提升研究,利用实地采集精化点和检核点高程信息,采用克里金插值法理论建立高程差模型,求取DEM格网高程差改正值,实现对DEM高程进行改正,达到DEM数据高程精化的目的,并对精化后的DEM高程进行了检测和验证,实验达到了预期效果。     

倾斜摄影测量技术在大比例尺地形图测绘中的应用

作为国际测绘领域近些年新兴的高新技术,倾斜摄影测量技术已应用于城市快速三维建模中。由于目前常用的大比例尺地形图测绘方法不能同时满足快速成图的时间和成本要求,本文提出了一种利用倾斜摄影测量技术测绘大比例尺地形图方法,充分发挥无人机倾斜摄影测量技术灵活、成本低、高效的优点,倾斜影像可自动生成三维模型和点云,简化了后续绘图工作。评定试验得到的岢岚县大比例尺地形图可知,成果平面精度达到0.140 m,高程精度达到0.150 m,符合大比例尺地形图精度要求,适合快速测绘小区域大比例尺地形图。     

提高大比例尺地形图等高线质量的方法初探

提出利用DEM数据直接生产大比例尺地形图等高线质量的几个技术问题,通过对问题产生根源的分析,探讨并总结出了解决问题的方法,用于批量生产。     

利用ASTER立体像对提取相对DEM及正射影像地图制作

本文探讨在PCIGeomatica软件支持下,应用四川省泸州地区ASTER立体像对数据自动提取DEM及其正射影像地图制作。通过与当地实测地形图(1∶50000)比较,表明在平坦地区ASTER DEM与实测地形图吻合很好;在高程变化较大的区域由于太阳高度、方位影响和ASTER后视成像存在着较大的叠掩和阴影效应,ASTER DEM和实测DEM存在一些差异,但总体上可以满足中小比例尺(1∶500,000到1∶1000,000)地图应用。ASTER的应用为DEM的快速提取和正射影像地图制作提供了一种新的途径。     

利用1:2000数字地形图编制1:10000建库数据的实践与探索

目前,我国很多城市拥有适时更新的大比例尺数字地形图,如何利用已有资源快捷地编制中小比例尺的建库数据,值得研究和探讨.文中给出在MicroStation中利用1:2 000数字地形图编制1:10 000建库数据的方法与技术.使用数字高程模型编制等高线并结合地形和高程模型进行等高线的编辑、裁剪,采取从数字地形图上直接拾取和...     

基于地形图数据库的跨比例尺级别缩编更新方法研究

针对利用1：500地形图快速更新其他比例尺地形图的需求,本文提出了基于地形图数据库的同比例尺级别和跨比例尺级别全自动缩编更新入库的方法。通过设计地形图模板及过渡模板,定义地物要素综合取舍转换规则,开发自动缩编软件模块,定制自动缩编更新任务,利用数据库中测量更新范围线自动下载地形图数据进行缩编及更新入库,实现大比例尺地形图依次缩编更新获取多种比例尺地形图的目标。本文提出的技术方法已在长沙市城市基础地理信息数据库更新工作中得到了验证,为采用缩编方式快速获取多样性地理信息数据提供了技术经验。     

Assessment of Shuttle Radar Topography Mission Elevation Data Based on Topographic Maps in Turkey

Depending on scale, topographic maps depicting the shape of the land surfaces of the Earth are produced from different data sources. National topographic maps at a scale of 1:25 000 (25K maps) produced by General Command of Mapping are used as the base map set in Turkey. This map set, which consists of approximately 5500 sheets, covers the whole country and is produced using photogrammetric methods. Digital Elevation Models (DEMs) created from these maps are also available. Recently, another data source, Synthetic Aperture Radar (SAR) interferometric data, has become more important than those produced by conventional methods. The Shuttle Radar Topography Mission (SRTM) contains elevation data with 3 arc-second resolution and 16 m absolute height error (90 percent confidence level). These data are freely available via the Internet for approximately 80 percent of the Earth's land mass. In this study, SRTM DEM was compared with DEM derived from 25K topographic maps for different parts of Turkey. The study areas, each covering four neighboring 25K maps, and having an area of approximately 600 km², were chosen to represent various terrain characteristics. For the comparison, DEMs created from the 25K maps were obtained and organized as files for each map sheet in vector format, containing the digitized contour lines. From these data, DEMs in the resolution of 3 arc-second were created (25K-DEM), in the same structure as the SRTM DEM, allowing the 25K-DEMs and the SRTM DEM to be compared directly. The results show that the agreement of SRTM DEM to the 25K-DEM is within about 13 m, which is less than the SRTM's targeted error of 16 m. The spatial distribution of the height differences between SRTM-DEM and the 25K-DEM and correlation analysis show that the differences were mainly related to the topography of the test areas. In some areas, local height shifts were determined.     

Accuracy analysis, dem generation and validation using russian tk-350 stereo-images

TK-350 stereo-scenes of the Zonguldak testfield in the north-west of Turkey have been analysed. The imagery had a base-to-height ratio of 0·52 and covered an area of 200 km × 300 km, with each pixel representing 10 m on the ground. Control points digitised from 1:25 000 scale topographic maps were used in the test. A bundle orientation was executed using the University of Hanover program BLUH and PCI Geomatica OrthoEngine AE software packages. Tests revealed that TK-350 stereo-images can yield 3D geopositioning to an accuracy of about 10 m in planimetry and 17 m in height. A 40 m resolution digital elevation model (DEM) was generated by the PCI system and compared against a reference DEM, which was derived from digitised contour lines provided by 1:25 000 scale topographic maps. This comparison showed that accuracy depends mainly on the surface structure and the slope of the local terrain. Root mean square errors in height were found to be about 27 and 39 m outside and inside forested areas, respectively. The matched DEM demonstrated a systematic shift against the reference DEM visible as an asymmetric shift in the frequency distribution. This is perhaps caused by the presence of vegetation and buildings.     

Historic Landscape Reconstruction and Visualisation, West Oxfordshire, England

As part of the Wychwood Project in West Oxfordshire, England, aerial photography and historic maps are being used to reconstruct landscape change in the former medieval Royal Hunting Forest of Wychwood. An important objective of the project is to stimulate local interest in Wychwood and promote understanding of its evolution, thereby encouraging the support of stakeholders in the design of future landscapes. The parish of Leafield was selected to develop and test a method for reconstructing and visualising past and present landscapes to present to the public for evaluation and comparison. Leafield contains fine examples of both early and late enclosure landscapes and underwent large-scale disafforestation following the Enclosure Act of 1856. Ordnance Survey (O.S.) 1:10000 Landform Panorama contour data were used to create a digital elevation model (DEM) of the parish using ArcView 3D Analyst, enabling the user to create perspective views of the landscape from any height and viewing angle. Contemporary aerial photography was scanned and geo-rectified to create an overlay for 'draping' onto the DEM. Historical maps provided the reference for modifying the aerial photography using the PaintShop Pro graphics package. This paper presents and reviews the results and compares the method with other techniques, including VRML.     

关于DEM数据质量检查内容和方法的探讨

生产方式、资料精度、生产人员素质都会影响DEM数据的最终质量。本文结合多年的DEM数据质量检查工作,从检查内容出发,结合检查方法探讨DEM的质量控制。并在此基础上给出了ArcGIS平台下的检查方法,提出了适合程序实现的高程异常值探测新方法,有助于提高DEM数据质量检查的效率,对生产单位在DEM数据生产过程中避免出现一些技术问题有一定的借鉴作用。     

地形特征提取的一种简易算法

地形特征作为基本地理要素,从DEM数据中提取其隐含的地形结构信息是非常重要的。本方法采用距离倒数加权法建立格网DEM,提出一种直接比较高程值来提取地形特征的简易算法,并利用差分算法计算坡度和坡向,通过V isual C++软件平台,编程实现格网DEM地形特征的自动提取,进行三维立体显示。该算法易于编程实现,数据结构简单,程序运行效率高,提取结果与真实地形基本拟合。     

基于RD模型的SAR影像正射纠正研究

介绍了基于RD模型进行SAR影像正射纠正的基本原理,并将不同方案的试验结果进行定量分析.实验研究表明,利用RD模型进行SAR影像正射纠正是正确、有效的,利用稀少控制点便能获得高精度.不使用任何控制点和DEM,只利用卫星参数进行纠正,导致系统误差大,在实际生产中的应用不广泛.高程误差对平面位置误差影响较大,DEM的高程误差越小,DOM精度越高.参考DEM的高程误差是DOM产品精度的关键因素.     

煤层顶底板DEM二维光照渲染制图方法

煤层顶底板等高线图是煤矿企业用于生产决策的一种常用图纸,这种图的直观性较差,难以阅读。参照Tanaka明暗等值线图的方法提出一种基于二维显示的煤层底板DEM的光照渲染制图方法。该方法通过假定光源所处的位置,并计算DEM的三角面片的法向,进而求得三角面片的亮度,然后以填充绘制的方式将所有三角形以二维的方式绘制出来。这种方法具有显示效率高、编程简单、易于图层叠加、效果较Tanaka法逼真等优势。     

A practical method for SRTM DEM correction over vegetated mountain areas

Digital elevation models (DEMs) are essential to various applications in topography, geomorphology, hydrology, and ecology. The Shuttle Radar Topographic Mission (SRTM) DEM data set is one of the most complete and most widely used DEM data sets; it provides accurate information on elevations over bare land areas. However, the accuracy of SRTM data over vegetated mountain areas is relatively low as a result of the high relief and the penetration limitation of the C-band used for obtaining global DEM products. The objective of this study is to assess the performance of SRTM DEMs and correct them over vegetated mountain areas with small-footprint airborne Light Detection and Ranging (Lidar) data, which can develop elevation products and vegetation products [e.g., vegetation height, Leaf Area Index (LAI)] of high accuracy. The assessing results show that SRTM elevations are systematically higher than those of the actual land surfaces over vegetated mountain areas. The mean difference between SRTM DEM and Lidar DEM increases with vegetation height, whereas the standard deviation of the difference increases with slope. To improve the accuracy of SRTM DEM over vegetated mountain areas, a regression model between the SRTM elevation bias and vegetation height, LAI, and slope was developed based on one control site. Without changing any coefficients, this model was proved to be applicable in all the nine study sites, which have various topography and vegetation conditions. The mean bias of the corrected SRTM DEM at the nine study sites using this model (absolute value) is 89% smaller than that of the original SRTM DEM, and the standard deviation of the corrected SRTM elevation bias is 11% smaller.     

基于无人机航测及水下地形测量的水利工程高精度DEM构建研究

DEM是水利行业最主要的基础地理数据之一,本研究根据无人机航测构建密集点云,再对密集点云进行滤波处理,分类地面点,派生出高精度地面DEM,结合水下地形测量,绘制水下地形图,插值得到研究区高精度河道DEM。对地面DEM和河道DEM进行叠加处理,得到研究区整体DEM数据,通过质量检查可知,DEM的高程精度处于较高的水平。本研究工作提出的DEM构建方法,大大减少了野外地面点的测绘工作,作业效率高、DEM精度高,数据具有高时效性,为各项水利工作的开展提供了保障。     

激光雷达测量技术及其应用研究

对激光雷达测量技术的发展进行了概括 ,介绍了激光雷达测量技术的原理 ,探讨了利用激光雷达进行堆体体积测量的技术和方法 ,在此基础上发展了一个激光雷达测量系统 ,并在实际测量工作中进行了应用。实验表明 ,激光雷达测量技术与传统的测量方法相比 ,在测量精度、自动化程度和测量数据可视化等方面具有明显的优点 ,并且极大地减轻了劳动强度 ,提高了工作效率。