一种基于DEM汇水累积量的径流节点提取方法

快速有效地提取径流节点,对进行水系的形态和属性特征研究具有重要意义。已有的研究发现:径流节点在汇水累积量上具有显著的突变性和多向汇集性特征,在充分考虑此水文特征的基础上,本文运用GIS窗口分析的方法原理,设计了可行的基于高精度DEM数据的径流节点提取方法,完成了对实验样区DEM数据的径流节点提取。通过与实测的径流节点数量和分布的结果对比,验证了该方法具有理想的精度,同时具有较高的执行效率。     

DEM水文分析中一种有效消除伪水道的简易方法

宽广河谷平坦地形区的存在,对基于DEM提取的水系结构产生了严重影响,目前国内外已提出很多方法来处理这种平坦地形情况。在对这些方法进行总结回顾的基础上,提出一种简易的伪水道消除方法。该方法是在常用的河网提取算法的基础上,采用缓冲区分析和栅格叠置分析原理实现河网的二次有效提取。实例研究表明,该方法原理简单、易于操作实现、效果明显,使基于DEM在宽广河谷区生成的河网结构趋于合理,河网提取结果更加准确。     

基于均值变点分析的三峡库区河网提取研究

均值变点是最常见最直观的一种类型,它以平均值为分析对象,通过计算整个样本数据的方差(S)与分段样本的统计量(Si)之差来确定变点,变点的存在会使S和Si的差距增大。本文以SRTM DEM数据作为基本的地形数据,借助Arc Hydro Tools扩展模块,研究基于地表径流漫流模型的数字河网提取方法,采用均值变点分析法确定提取河网的阈值,并对结果进行分析。经对比发现,提取的主干河网与1∶250 000地形图主干上吻合较好,次流上更具真实性,提取结果可以用于各种地形分析。     

矢量河网渐进式传输的多尺度表达模型

矢量河网数据渐进式传输是制图综合的逆过程,从几何特征出发化简曲线的方法忽略了曲线的形态特征。鉴于此,以曲线轴线为基准,基于曲线弯曲层次化提取河流曲线数据,并将提取的曲线数据分层组织,构建结合目标层和几何细节层的河网多尺度表达模型。基于该模型开发了矢量河网数据的渐进式传输系统,验证了该方法的有效性。     

基于DEM的川西山地河网信息提取

基于DEM数据和D8算法,对研究区河网信息进行提取。这种方法主要是通过研究区集水面积与河网密度、河源密度二阶导数关系确定集水面积的阈值,避免了利用DEM提取流域河网时对阈值确定的反复过程,有助于模拟结果的有效性和准确性;不同集水面积阈值对确定主河道的空间位置影响较小,但对河网提取的详细程度具有重要影响,集水区面积阈值越大,河网就越稀疏。     

基于三维激光扫描的建筑物变形监测方法研究

提出一种基于中轴线上节点坐标偏移的方法提取变形信息,给出利用三维激光扫描进行建筑物变形监测的实施步骤,通过实验分析,结果表明该方法切实可行,精度能够满足变形监测实际要求.     

基于DEM的流域特征提取研究——以贵州省普定县后寨河流域为例

本文以喀斯特后寨河流域为例,探讨了在Arcgis 9.0环境下从数字高程模型(DEM)中提取流域特征的详细过程,包括:DEM的生成和预处理、水流方向的确定、汇流累积量分析、河网的提取和子流域的划分以及落水洞的计算。经分析得到了研究区域河网特征以及研究区其他常用的流域特征信息,与实际河流水系特征基本吻合,从而证明该方法在分析流域的河网水系结构特征时具有一定的应用价值。     

基于流域边界分析的山脊线提取方法研究

针对以往基于DEM数据提取山脊线存在的平行效应或设置参数过多、自动化程度较低等问题,提出了一种基于流域边界分析的山脊线提取方法.实验结果表明,该方法能得到连续的山脊线,且与DEM的地形走向保持一致,避免了脊线段断续以及平坦地段出现平行效应等问题;相同密度的山脊线能与河网相互有效衔接,形成可概括地形的骨架线网络;不同汇流阈值的河网可获得不同面积大小的流域边界,从而形成详略程度不一的山脊线网络,可为地形综合研究提供了新的思路.     

基于ArcSWAT的漓江流域河网水系自动提取对比研究

流域水系提取是山洪预报、分布式水文模拟等研究的基础和关键。基于SRTM_V4 DEM和ASTER GDEM两种数字高程数据,运用ArcSWAT对漓江流域水系进行提取,用河网套合差方式对提取结果进行评价。结果表明,通过引入该地区矢量图层进行胁迫的方法所提取的河网水系精度最高;在无辅助信息胁迫条件下SRTM_V4 DEM数据对地形的表达比较准确,但通过修正后的ASTER GDEM数据更适用于流域水系提取。     

基于DLG水系的DEM修正方法研究

在利用ArcGIS等地形分析软件对DEM数据进行径流网络的自动提取时,由于水流方向算法的局限,在地势较平缓区域往往会出现平行河现象,造成平缓地区水系的误差.本文提出一种通过对原始DEM栅格数据进行河网特征嵌入与高程修正来实现对水系误差快速修正的方法.     

基于对偶拓扑结构的路网路段重要性评估方法

现有的路网路段重要性评估方法考虑的是路网中的路段的统计特性或路网的局部结构对重要性的影响。在路段的重要性与路网的全体路段相关联的基础上,提出m阶邻居节点的复杂路网路段重要度评估方法。为验证算法的有效性,实验仿真采用成都市路网的对偶拓扑结构,在1 484个路段中提取10条关键路径对评估方法进行验证。评估结果显示:与度值法、介数法相比,该方法能显著地区分复杂路网中路段之间的重要性差异,准确地确定网络中的关键路径,具有更高的评估准确性。     

Runoff modelling of a small watershed using satellite data and GIS

This study was conducted for the Nagwan watershed of the Damodar Valley Corporation (DVC), Hazaribagh, Bihar, India. Geographic Information System (GIS) was used to extract the hydrological parameters of the watershed from the remote sensing and field data. The Digital Elevation Model (DEM) was prepared using contour map (Survey of India, 1:50000 scale) of the watershed. The EASI/PACE GIS software was used to extract the topographic features and to delineate watershed and overland flow-paths from the DEM. Land use classification were generated from data of Indian Remote Sensing Satellite (IRS-1B—LISS—II) to compute runoff Curve Number (CN). Data extracted from contour map, soil map and satellite imagery, viz. drainage basin area, basin shape, average slope of the watershed, main stream channel slope, land use, hydrological soil groups and CN were used for developing an empirical model for surface runoff prediction. It was found that the model can predict runoff reasonably well and is well suited for the Nagwan watershed. Design of conservation structures can be done and their effects on direct runoff can be evaluated using the model. In broader sense it could be concluded that model can be applied for estimating runoff and evaluating its effect on structures of the Nagwan watershed.     

Drainage Network Modelling for Water-Sensitive Urban Design

While drainage network models may be relatively easy to assemble as a prerequisite to site selection for infrastructure supporting suburbanisation with Water-Sensitive Urban Design (WSUD), this is unlikely to be the case if the terrain is very subdued. Both ab initio and retro-fit WSUD implementation for such terrain refers, in the first instance, to a drainage network model that includes information on the scope for optimising residential space while conforming to: (1) statutory planning rules about the provision of public open space; and (2) WSUD drainage network design such that runoff waters are retained long enough to allow at least temporary storage. It is shown in this research that a technique applied to condition a LiDAR DEM can accurately model the drainage network of a basin at the land-parcel scale. The drainage network for ab initio WSUD is best defined using multi-flow modelling, with the relative significance of stream segments indicated by their stream order derived using the Strahler method. In contrast, when applying the retro-fit WSUD, the relative significance of segments given by the Shreve stream order method was found to be more useful. The approaches described in this article are designed to support the initial site planning stage and avoid the need for immediate and expensive detailed field survey. At the same time they can be deployed to show how much scope there is for WSUD retro-fit in established housing areas up-stream of an infill development area. Thus, basin-wide appraisal is facilitated and the need for earthmoving is minimised.     

A stream ordering approach based on network analysis operations

Stream ordering is a technique for characterizing the constituent parts of a drainage network. Network analysis remains one of the most popular and persistent research and application areas in geographic information science. In this study, a new stream ordering approach based on geographic information systems tools and network analysis operations is proposed. The new method combines the concepts of modern network analysis operations, which mainly deal with derivations of the best route solution, and the previous stream ordering techniques. In this context, the method readily identifies the channel heads hierarchically in order to derive main stream channel and its tributaries, and assigns a unique order for each stream on the network.     

一种顾及道路复杂度的增量路网构建方法

针对传统路网采集和更新需要昂贵的实地测量以及大量的后续内业处理问题,提出了一种从大规模粗糙轨迹数据中自动生成路网的方法。该方法包含轨迹滤选和路网增量构建两步:第1步通过构建空间、时间、逻辑约束的规则模型,在消除数据中的噪音和冗余的同时,将原始轨迹进行合理分割,滤选形成规范轨迹集合;第2步基于信息熵计算轨迹点周围道路的复杂度,据此自动调节道路分割参数,不断将新产生的路段加入到路网,同时计算道路平均交通流量和速度等路况信息,遍历各规范轨迹的定位点重复以上处理过程,最终得到完整路网。通过昆明市200辆出租车采集的约6851万条轨迹数据进行路网构建试验,并与OpenStreetMap数据比较,证明了本文方法的有效性。与已有典型方法比较,本文方法能用更少节点提取更高质量的路网。     

Catchment storm runoff modelling using the geomorphologic instantaneous unit hydrograph

A lumped empirical model, the Geomorphologic Instantaneous Unit Hydrograph (GIUH) rainfall-runoff model, is developed for the Can Le catchment in the upstream region of the Sai Gon river Basin (Vietnam). This model can serve to simulate catchment runoff into the Dau Tieng Reservoir and can be used as a flood forecasting tool for the ungauged Can Le catchment. The GIUH couples geomorphology and hydrology quantitatively. The obtained Unit Hydrograph is based on Horton's morphometric parameters; bifurcation, length and area ratios. A new functionality within the ILWIS GIS-RS package, namely ‘DEM-hydro processing’, is applied to effectively process a Digital Elevation Model to extract these ratios from the drainage network. To supplement the limited field data available, various satellites images have been used such as ASTER, SRTM (Shuttle Radar Topography Mission) and METEOSAT 5. A short field campaign to collect missing ground data was executed between September and October 2005. The data collected included discharge (and stage – discharge curve), meteorological data, soil, land use information that are used for paramerisation, calibration and validation of the GIUH. The model was successfully applied for the Can Le catchment. Using the Horton's morphometric parameters derived from the DEM with estimated overland and stream flow velocities, the model is easy-to-use.     

构建城市地表产流和汇流模型探讨

本文基于空间离散化理论与方法和DEM技术,将城市地表划分成一系列网格单元,从水平方向和垂直方向研究城市地表空间位置和综合因素的空间离散化描述、表达以及参数模型化处理机制,创新构建出一个特定的以DEM空间离散化解析函数式表达的、综合顾及城市地表地形特征、下垫面物质形态和人工建筑物等因素的地表产流和汇流模型,实施城市地表产流和汇流的路径以及水流累积量的分析计算。     

A Pattern‐Based Approach for Matching Nodes in Heterogeneous Urban Road Networks

This article presents an approach to hierarchical matching of nodes in heterogeneous road networks in the same urban area. Heterogeneous road networks not only exist at different levels of detail (LoD), but also have different coordinate systems, leading to difficulties in matching and integrating them. To overcome these difficulties, a pattern‐based method was implemented. Based on the authors' previous work on detecting patterns of divided highways, complex road junctions, and strokes to eliminate the LoD effect of road networks, the proposed method extracts the local networks around each node in a road network and uses them as the matching units for the nodes. Second, the degree of shape similarity between the matching units is measured using a Minimum Road Edit Distance based on a transformation. Finally, the proposed method hierarchically matches the nodes in a road network using the Minimum Road Edit Distance and eliminates false matching nodes using M‐estimators. An experiment involving matching heterogeneous road networks with different LoDs and coordinate systems was carried out to verify the validity of the proposed method. The method achieves good and effective matching regardless of differences in LoDs and road‐network coordinate systems.     

犯罪网络构建及其时空分析——以入室盗窃为例

提出了一种基于时空影响范围的网络构造方法,构造了一种基于节点影响强度的犯罪传输网络,并引入复杂网络的度、平均度、聚集系数等特征参数分析犯罪传输网络。提取了犯罪预测过程中需要关注的重要节点,分析了其时间分布和空间分布特性,研究结果表明:（1）近邻的时空单元的犯罪率具有一定的关联关系。其中,节点的出度与入度具有正相关性,因此可以引入邻居时空单元的犯罪密度以量化和分析犯罪规律。（2）节点的度分布具有无标度特性,犯罪较少的小区也可能出现度较大的节点,而节点的度与未来犯罪率具有较大的关联性。因此,即便犯罪率较低的小区也要关注节点的度变化情况。（3）犯罪聚集系数大小与未来犯罪率的变化具有一定的关联性,较高的聚集系数意味着未来犯罪状态的变化。