A new GIS-compatible methodology for visibility analysis in digital surface models of earth sites

As a GIS tool,visibility analysis is used in many areas to evaluate both visible and non-visible places.Visibility analysis builds on a digital surface model describing the terrain morphology,including the position and shapes of all objects that can sometimes act as visibility barriers.However,some barriers,for example vegetation,may be permeable to a certain degree.Despite extensive research and use of visibility analysis in different areas,standard GIS tools do not take permeability into account.This article presents a new method to calculate visibility through partly permeable obstacles.The method is based on a quasi-Monte Carlo simulation with 100 iterations of visibility calculation.Each iteration result represents 1%of vegetation permeability,which can thus range from 1%to 100%visibility behind vegetation obstacles.The main advantage of the method is greater accuracy of visibility results and easy implementation on any GIS software.The incorporation of the proposed method in GIS software would facilitate work in many fields,such as architecture,archaeology,radio communication,and the military.

A TECHNIQUE OF DIGITAL SURFACE MODEL GENERATION

It is usually a time-consuming process to real-time set up 3D digital surface model(DSM) of an object with complex surface.On the basis of the architectural survey project of"Chilin Nunnery Reconstruction",this paper investigates an easy and feasible way,that is,on project site,applying digital close range photogrammetry and CAD technique to establish the DSM for simulating ancient architectures with complex surface.The method has been proved very effective in practice.

An Adaptive and Image-guided Fusion for Stereo Satellite Image Derived Digital Surface Models

The accuracy of Digital Surface Models(DSMs)generated using stereo matching methods varies due to the varying acquisition conditions and configuration parameters of stereo images.It has been a good practice to fuse these DSMs generated from various stereo pairs to achieve enhanced,in which multiple DSMs are combined through computational approaches into a single,more accurate,and complete DSM.However,accurately characterizing detailed objects and their boundaries still present a challenge since most boundary-ware fusion methods still struggle to achieve sharpened depth discontinuities due to the averaging effects of different DSMs.Therefore,we propose a simple and efficient adaptive image-guided DSM fusion method that applies k-means clustering on small patches of the orthophoto to guide the pixel-level fusion adapted to the most consistent and relevant elevation points.The experiment results show that our proposed method has outperformed comparing methods in accuracy and the ability to preserve sharpened depth edges.

Using UAVs for detection of trees from digital surface models

A difficult problem in forestry is tree inventory.In this study, a GoProHero attached to a small unmanned aerial vehicle was used to capture images of a small area covered by pinus pinea trees. Then, a digital surface model was generated with image matching. The elevation model representing the terrain surface, a ‘digital terrain model’,was extracted from the digital surface model using morphological filtering. Individual trees were extracted by analyzing elevation flow on the digital elevation model because the elevation reached the highest value on the tree peaks compared to the neighborhood elevation pixels. The quality of the results was assessed by comparison with reference data for correctness of the estimated number of trees. The tree heights were calculated and evaluated with ground truth dataset. The results showed 80% correctness and 90% completeness.

Study on the Digital Manufacturing System of Ship Model Surface

Because a ship model surface (SMS) is a large double-curved 3-D surface,the machining efficiency of the cur- rent handcraft manufacturing method are very low,and the precision is difficult to control also.In order to greatly improve the machining efficiency and precision of SMS,based on the CAD/CAM/CNC technology,this paper proposed a model of SMS digi- tal manufacturing system,which is composed of five functional modules (preprocess module,CAD module,CAM module,post- process module and CNC module),and a twin-skeg SMS as an example,the key technologies & design principle of the nodtules were investigated also Based on the above research works,the first set of 4-axis SMS Digital Manufacturing System in China has been successfully developed,which can reduce the machining time of the twin-skeg SMS from 30 working days needed for the cur- rent handcrafting manufacturing method to 8 hours now,and which can control more effectively the precision of SMS also.

Primary safe criterion of earth-brushing flight for flying vehicle over digital surface model

In modern terrain-following guidance it is an important index for flight vehicle to cruise about safely and normally. On the basis of a constructing method of digital surface model (DSM), the definition, classification and scale analysis of an isolated obstacle threatening flight safety of terrain-following guidance are made. When the interval of vertical-and cross-sections on DSM is 12. 5 m, the proportion of isolated obstacles to the data amount of DSM model to be loaded is optimal. The main factors influencing the lowest flying height in terrain-following guidance are analyzed, and a primary safe criterion of the lowest flying height over DSM model is proposed. According to their test errors, the lowest flying height over 1:10 000 DSM model can reach 40. 5 m^45. 0 m in terrain-following guidance. It is shown from the simulation results of a typical urban district that the proposed models and methods are reasonable and feasible.

Evaluating the Impacts of Using Different Digital Surface Models to Estimate Forest Height with TanDEM-X Interferometric Coherence Data

In our previous studies, we demonstrated the usefulness of TanDEM-X interferometric bistatic mode with single polarization to obtain forest heights for the purposes of large area mapping. A key feature of our approach has been the use of a simplified Random Volume Over Ground(RVOG) model that locally estimates forest height. The model takes TanDEM-X interferometric coherence amplitude as an input and uses an external Digital Surface Model(DSM) to account for local slope variations due to terrain topography in order to achieve accurate forest height estimation. The selection of DSM for use as a local slope reference is essential, as an inaccurate DSM will result in less accurate terrain-correction and forest height estimation. In this paper, we assessed TanDEM-X height estimates associated with scale variations in different DSMs used in the model over a remote sensing supersite in Petawawa, Canada. The DSMs used for assessments and comparisons included ASTER GDEM, ALOS GDSM, airborne DRAPE DSM, Canadian DSM and TanDEM-X DSM. Airborne Laser Scanning(ALS) data were used as reference for terrain slope and forest height comparisons. The results showed that, with the exception of the ASTER GDEM, all DSMs were sufficiently accurate for the simplified RVOG model to provide a satisfactory estimate of stand-level forest height. When compared to the ALS 95th height percentile, the modeled forest heights had R2 values greater than 80% and Root-Mean-Square Errors(RMSE)less than 2 m. For a close similarity in slope estimation with the ALS reference, coverage across Canada and open data access, the 0.75 arc-second(20 m) resolution Canadian DSM was selected as a preferred choice for the simplified RVOG model to provide TanDEM-X height estimation in Canada.

Three-Dimensional TIN Algorithm for Digital Terrain Modeling

The problem of taking an unorganized point cloud in 3D space and fitting a polyhedral surface to those points is both important and difficult. Aiming at increasing applications of full three dimensional digital terrain surface modeling, a new algorithm for the automatic generation of three dimensional triangulated irregular network from a point cloud is pro- posed. Based on the local topological consistency test, a combined algorithm of constrained 3D Delaunay triangulation and region-growing is extended to ensure topologically correct reconstruction. This paper also introduced an efficient neighbor- ing triangle location method by making full use of the surface normal information. Experimental results prove that this algo- rithm can efficiently obtain the most reasonable reconstructed mesh surface with arbitrary topology, wherein the automati- cally reconstructed surface has only small topological difference from the true surface. This algorithm has potential applica- tions to virtual environments, computer vision, and so on.

Numerical Calculation of Channel Dredging Volume Using 3D Digital Stratum Model

Prediction of channel dredging volume is critical for project cost estimation. However, many proposed approximate methods are not accurate. This paper presents a novel numerical method to accurately calculate the dredg- ing volume using a 3D stratum model (DSM) and a channel surface model. First, the 3D DSM is constructed rapidly yet accurately from non-uniform rational B-splines (NURBS) surfaces through Boolean operation between a physical terrain model and a stratum surfaces model. Then, a parametric channel surface model is built from cross-section data and a channel center line using code implemented in the VC++ programming language. Finally, the volumes of different types of physical stratums can be calculated automatically and hierarchically to determine the dredging volume. Practical application shows that the DSM method is more precise and faster compared to the section method, and that the implementation of the developed software provides an interactive graphical user interface and visual presentation.

Facets of Uncertainty in Digital Elevation and Slope Modeling

This paper investigates the differences that result from applying different approaches to uncertainty modeling and reports an experimental examining error estimation and propagation in elevation and slope, with the latter derived from the former. It is confirmed that significant differences exist between uncertainty descriptors, and propagation of uncertainty to end products is immensely affected by the specification of source uncertainty.

DTM在开采沉陷可视化预计中的应用

数字地面模型(DTM)具有强大的三维可视化分析和空间模拟功能,它可以代替等高线对地形表面的描述,能满足对等高线数据相同的各种需求。为了充分地利用地质、矿山等许多领域的三维原始数据,以开采沉陷预计为研究对象,首先提出了将DTM用于地表移动变形可视化预计的意义,然后对其DTM构造的思路和方法进行了研究,最后,结合实例,介绍了将DTM用于开采沉陷可视化预计可以得到的最终成果。

基于体素的森林地区机载LiDAR数据DTM提取

机载LiDAR是一种能够直接、快速获取被测目标三维空间信息的主动式遥感技术,被广泛用于获取高精度的数字地面模型,但是在植被比较密集、地势比较陡峭的森林地区,能够穿透植被到达地表的激光脚点数量较开阔区域少,对于提取精确的DTM有一定难度。该文提出一种继承式多分辨率体素滤波算法,从机载激光扫描数据中获取森林地区的DTM。该方法将激光点云数据划分为不同分辨率等级的体素,以体素为单位通过与邻域体素的高程加权均值比较,剔除植被点,保留地面点,从而获取森林地区的DTM。实验证明该滤波方法能够有效地提取森林地区的DTM。

基于非均匀B样条曲面的DTM内插模型

对非均匀B样条曲面在数字地面模型(DTM)内插中的应用进行了研究,首先探讨了非均匀B样条曲面基本理论及其最小二乘解法,然后提出了基于非均匀B样条曲面的DTM内插算法,最后利用提出的B样条算法与目前一些常用的内插算法,对数学曲面与实际地形进行了试验和比较.试验结果表明B样条算法具有良好的精度和稳定性,能较好地改善在构建DTM时常出现的“梯田”现象.

基于DTM的矿山排土场设计

针对矿山排土场(废石场)设计的方法和要求,探讨了将地理信息系统的数字地面模型(digitalterrain model,DTM)技术运用于矿山排土场的选址设计方案的可行性。以矿区地形数字高程模型以及排土场设计要素为依据,模拟出设计面的数字高程模型,并且计算出了相应的排土场容量。采用该技术可提高矿山排土场设计的工作效率并具有较高的准确性和智能化水平。

基于DTM的城市网格化管理部件数据的质量评价

城市网格化管理是一种数字化城市管理模式,是我国数字城市技术应用领域的重大突破,在国际上处于领先地位,对其部件数据质量评价与控制具有重要的现实意义。针对城市网格化管理部件数据的地域性分布特点,运用空间插值算法,提出一种基于数字地面模型(DTM)的城市网格化管理部件数据质量评价方案(以上海市为例)。实验结果表明,该方案更能准确的度量整体数据的质量。

考虑边界约束的DTM三角网模型生成算法研究

无约束的数字地面模型(DTM)空间三角网算法生成的三角网外围边界是一个凸壳,这对于实际区域为凹多边形的区域(如公路弯道)会有较大的模拟失真。文章提出一种改进的算法,通过分析实际边界多边形的精细度影响因素,导出确定区域相邻离散点平均边长的计算方法,进而确定一个边界多边形边长的最大值。以该边长最大值对无约束的三角网外围边界进行边长约束,最终生成新的空间三角网。实验表明,该算法是有效可行的。

基于LIDAR点云海岛的DTM生成算法研究

提出一种基于LIDAR点云的海岛DTM生成算法。先将LIDAR点云数据规则格网化,对每个格网内的点云数据进行三次曲面拟合,在拟合基础上初步区分每一格网内的地面点与非地面点。若靠近格网边缘处有足够多的地面点,则认为此格网内地面点与非地面点可分,记录其中被初步归为地面类的点;若格网四周没有足够多的地面点,则用其邻域格网内初步确定的地面点推测本格网地面信息,并以推知的地面信息确定本格网内点的归属。初步确定的地面点决定了初始地形,在初始地形上对点云进行迭代曲面拟合滤波,从而精确识别地面点及非地面点,平滑地面点数据得到最终的DTM。

DTM在开采沉陷可视化预计中的应用研究

以开采沉陷为研究对象,提出了将数字地面模型DTM(Digital Terrain Model)用于地表移动变形可视化预计的意义、DTM构造的思路和方法,以及将DTM用于开采沉陷可视化预计的应用进行了研究。

遥感影像与DTM的复合及其在矿山的应用

遥感 (RS)影像和数字地面模型 (DTM )的复合包括三方面 :由遥感影像生成数字地面模型 ;用数字地面模型来纠正遥感影像 ;遥感影像和数字地面模型配准应用。将遥感影像和数字模型复合可用于矿山测绘、地表沉陷监测、矿区土地复垦与生态重建、露天矿边坡监测、矿山三维仿真等方面 ,地理信息系统(GIS)是实现这些应用的技术平台。

三维数字地形图制作技术与DTM建模精度控制

针对传统纸上定线方法效率低及制约公路多方案比选的问题,通过对地形图数字化的原理分析,提出直接在AutoCAD平台制作三维数字地形图的实用技术,并研究应用纬地道路CAD软件构建不规则三角网DTM的建模精度控制。应用结果表明:地形图三维数字化技术可快捷完善地制作精度可靠的数字地形图,据此构建数字地面模型,可实现公路设计的内外业自动化作业,对缩短道路勘测设计周期、提高设计质量有实际意义。