DTM法土方量计算的工区边缘高程点选取问题与精度分析

DTM法土方量计算是工程施工中较为常用的一种方法,选取不同的高程点将获得不同的DTM,进而会影响到工区内土方量计算的精度。本文对不同工区的多种高程点选取方式进行了实验及分析,从中总结了一种较为有效的并兼顾精度的工区边缘高程点选取方法。     

The effect of short ground vegetation on terrestrial laser scans at a local scale

Terrestrial laser scanning (TLS) can record a large amount of accurate topographical information with a high spatial accuracy over a relatively short period of time. These features suggest it is a useful tool for topographical survey and surface deformation detection. However, the use of TLS to survey a terrain surface is still challenging in the presence of dense ground vegetation. The bare ground surface may not be illuminated due to signal occlusion caused by vegetation. This paper investigates vegetation-induced elevation error in TLS surveys at a local scale and its spatial pattern. An open, relatively flat area vegetated with dense grass was surveyed repeatedly under several scan conditions. A total station was used to establish an accurate representation of the bare ground surface. Local-highest-point and local-lowest-point filters were applied to the point clouds acquired for deriving vegetation height and vegetation-induced elevation error, respectively. The effects of various factors (for example, vegetation height, edge effects, incidence angle, scan resolution and location) on the error caused by vegetation are discussed. The results are of use in the planning and interpretation of TLS surveys of vegetated areas.     

Recovery of elevation from estimated gradient fields constrained by digital elevation maps of lower lateral resolution

Depth measurement techniques like stereo analysis and laser range scanning often yield a lateral resolution below image resolution. In contrast, shading-based methods estimate the elevation model at image resolution. We present a computationally efficient approach to recover a surface of high vertical and high lateral resolution from a noisy gradient field and independently measured elevation data of lower lateral resolution, relying on a minimization of the mean squared difference between the low-pass component of the surface obtained based on shading information and that of the independently measured elevation data. The presented method is compared to a reference approach that minimizes a weighted sum comprised of the mean squared difference between the low-pass components of the estimated gradient field and the optimized model, respectively. The presented algorithm is applied using lunar orbital image data and stereo elevation data and is evaluated regarding orbital laser altimeter measurements of high vertical accuracy.     

不同 Delaunay 三角网构建方法对土石方量计算差异研究

为了分析不同Delaunay三角网构建方法对土石方量计算的影响,叙述了目前三类Delaunay三角网构建方法---逐点插入法、三角网生长法和分而治之法的特点,建立了三角网土石方量计算公式。采用C＋＋语言进行了程序实现,分别计算了某建筑场地土石方量,三种方法生成三角形数目相同,土方量存在一定差异,但均在规范对土方计算要求的允许范围之内。三种三角网构建方法不同导致生成三角网局部的不同是土方量计算不一致的主要原因。这一研究成果具有重要的现实作用及意义。     

Semi-automatic Process for Hybrid DTM Generalization based on Structural Elements Multi-analysis

Abstract

The generalization of digital terrain models (DTMs) is a tool of great potential for simultaneous cartographic and photogrammetry generation processes at different scales, the main object of which is to feed different geographic information systems (GIS). These GIS enable multi-scale analysis and visualization through different data bases. This research proposes a semi-automatic DTM generalization process conditioned by a series of predefined parameters resulting in the generation of hybrid DTMs at different scales starting from a single cloud of points obtained through large-scale massive data acquisition processes. The generalization results obtained, applied on different areas of different relief, offer specific application ranks for each parameter with great precision, in contrast with DTMs obtained directly in each scale.     

最小二乘曲面拟合的LiDAR数据滤波方法

机载激光扫描技术(LiDAR)可直接获取数字表面模型,但要获得高精度的数字地面模型(DTM)需要滤波去除地物点,这是一项十分复杂和耗时的工作。本文提出一种基于二次多项式的局部最小二乘拟合滤波算法,对数据进行规则格网化处理,对每个格网的数据进行局部最小二乘拟合滤波处理,并缩小格网大小迭代进行滤波。实验结果表明提出的方法能得到很好的效果。     

Simulations using terrestrial geological analogues to assess interpretability of potential geological features of the Hermean surface restituted by the STereo imaging Camera of the SIMBIOSYS package (BepiColombo mission)

The BepiColombo space mission is one of the European Space Agency's cornerstone projects; it is planned for launch in 2013 to study the planet Mercury. One of the imaging instruments of BepiColombo is a STereo Camera (STC), whose main scientific objective is the global stereo mapping of the entire surface of Mercury. STC will permit the generation of a Digital Terrain Model (DTM) of Mercury's surface, improving the interpretation of morphological features at different scales and clarifying the stratigraphic relationships between different geological units.To evaluate the effectiveness of the STC-derived DTM for geological purposes, a series of simulations has been performed to find out to what extent the errors expected in the DTM may prevent the correct classification and interpretation of geological features. To meet this objective, Earth analogues (a crater, a lava cone and an endogenous dome) of likely components of the Hermean surface, small enough to be near the detection limit of the STC, were selected and a photorealistic three-dimensional (3D) model of each feature was generated using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) stereo images. Stereoscopic pairs of synthetic images of each feature were then generated from the 3D model at different locations along the BepiColombo orbit. For each stereo pair, the corresponding Hermean DTM was computed using image correlation and compared to the reference data to assess the loss of detail and interpretability. Results show that interpretation and quantitative analysis of simple craters morphologies and small volcanic features should be possible all along the periherm orbit arc. At the apoherm only the larger features can be unequivocally distinguished, but they will be reconstructed to a poor approximation.     

基于CASS的土石方多种计算方法与比较

对传统常规计算土方量的具体方法、算法原理、应用范围、计算步骤等进行对比分析,对其注意问题进行探讨,研究并总结常规方法的优缺点.     

应用DTM改善煤层自燃的热红外探测

根据遥感物理基础，提出了应用ＤＴＭ计算出地表的太阳辐射强度，并以此为依据校正ＴＭ第６波段的象元值，消除地形的影响，突出由煤层自燃引起的地表热异常，为灭火工程及火区动态监测提供信息和指导。文中选择了新疆准南煤田的硫磺沟火区为试验区，展示了研究的成果。     

曲面样条函数在DTM中的分析应用研究

本文介绍了曲面样条的数学原理，分析了其在DTM中的应用方法，即可用于空间内插和坡度，坡向分析。