基于三维遥感系统的泥石流土石量计算及影响范围模拟

结合三维遥感影像解译提出一种定量的泥石流土石量计算方法。在泥石流汇水区内对地形进行0次谷与1次谷划分,按可搬运的物质总量和一次降雨所能搬运的物质总量两种方式进行分析,使计算结果更加精细化;以数字高程模型(DEM)与降雨所搬运的土石总量作为影响范围模拟的基础,利用GIS空间分析功能分析泥石流汇水区的横截面面积及区域平面面积等地形参数,判别土石产出量与地形参数关系,实现泥石流影响范围的模拟。分析结果可为潜在泥石流危险区域评价预测提供参考。     

Vegetative succession and controlled fire in a glades ecosystem A geographical information system approach

Abstract

A geographical information system (GIS) approach was used successfully on a federal wilderness area in southwestern Missouri to examine vegetative succession relative to fire management in a glades ecosystem. Maps of vegetation were obtained by interpreting aerial photographs taken in 1938, 1958, 1966, 1975 and 1986. Maps of topography, streams, soils and the location of fires which burned during the period 1938 to 1986 were also procured from a variety of public agencies. All maps were digitized and incorporated into a raster-based GIS with 25 m pixels. It was concluded that (1) both glades and oak-hickory forest have an affinity for distinct physiographic areas and (2) fire can help decrease the rate of processes of natural succession which cause glades to convert to forest. The probable effects of controlled fire on three areas proposed by the Forest Service were evaluated and summarized.     

The smoothness of HASM

To smooth noises inherent in uniformly sampled dataset, the smoothness of high accuracy surface modeling (HASM) was explored, and a smoothing method of HASM (HASM-SM) was developed based on a penalized least squares method. The optimal smoothing parameter of HASM-SM was automatically obtained by means of the generalized cross-validation (GCV) method. For an efficient smoothing computation, discrete cosine transform was employed to solve the system of HASM-SM and to estimate the minimum GCV score, simultaneously. Two examples including a numerical test and a real-world example were employed to compare the smoothing ability of HASM-SM with that of GCV thin plate smoothing spline (TPS) and kriging. The numerical test indicated that the minimum GCV HASM-SM is averagely more accurate than TPS and kriging for noisy surface smoothing. The real-world example of smoothing a lidar-derived Digital Elevation Model (DEM) showed that HASM-SM has an obvious smoothing effect, which is on a par with TPS. In conclusion, HASM-SM provides an efficient tool for filtering noises in grid-based surfaces like remote sensing–derived images and DEMs.     

Measuring the significance of a divide to local drainage patterns

This article presents a framework for estimating a new topographic attribute derived from digital elevation models (DEMs) called maximum branch length (B _max). Branch length is defined as the distance travelled along a flow path initiated at one grid cell to the confluence with the flow path passing through a second cell. B _max is the longest branch length measured for a grid cell and its eight neighbours. The index provides a physically meaningful method for assessing the relative significance of drainage divides to the dispersion of materials and energy across a landscape, that is, it is a measure of ‘divide size’. B _max is particularly useful for studying divide network structure, for mapping drainage divides, and in landform classification applications. Sensitivity analyses were performed to evaluate the robustness of estimates of B _max to the algorithm used to estimate flow lengths and the prevalence of edge effects resulting from inadequate DEM extent. The findings suggest that the index is insensitive to the specific flow algorithm used but that edge effects can result in significant underestimation along major divides. Edge contamination can, however, be avoided by using an appropriately extensive DEM.     

瞬变电磁法探测复杂地形不积水采空区的应用

针对高密度电法在探测煤矿不积水采空区对地形有严格要求的实际情况下,在煤田地表条件较为复杂的地区,采用受地形影响较小的瞬变电磁法反映地下不积水采空区的电性特征的研究与应用就有了重要的实际意义。为此首先从瞬变电磁法的基本原理出发,介绍瞬变电磁法的基本公式和正演方法;其次,结合不积水采空区的地球物理特征,设计正演模型,根据计算结果提出在地形条件复杂,不适合高密度电法施工的地方,采用小线框、配合高发射频率和大发射电流的瞬变电磁方法,探测地下高阻目标体的电性特征,推断不积水采空区的分布;最后,结合实际工程进行瞬变电磁法探测煤矿不积水采空区的实践,得到结论与实际钻探结果相符。应用效果表明,瞬变电磁法在一定程度上能够完成煤矿不积水采空区的探测,对煤矿安全生产起到了的参考作用。     

Delineating groundwater potential zones in a hard-rock terrain using geospatial tool

Abstract

Geospatial techniques have become one of the leading tools in the field of natural sciences for assessment, monitoring and management of natural resources, particularly in groundwater research. The paper discusses the demarcation and assessment of groundwater potential zones using geospatial techniques in the Deccan Volcanic Province of Maharashtra, India, using multi-criteria analyses. The study incorporates integration of thematic information (geomorphology, lithology, drainage density, slope and lineaments) in a GIS environment in order to identify groundwater potential zones. The methodology adopted can be used as a rapid assessment tool in groundwater exploration and is helpful in predictive groundwater resource management. Multi-criteria evaluation techniques were used to integrate all the thematic layers. Individual themes and their corresponding categories were assigned a knowledge base ranking from 1 to 5, depending on their importance for groundwater potential. Using the Raster calculator tool in Arc GIS software, all thematic maps were integrated to produce a composite groundwater potential map of the study area. The identified groundwater potential zones were classified into four classes, from excellent to poor. The generated groundwater potential zones were validated with field checks and borewell/dugwell yield data, and showed consistency with the observations.

Citation Singh, P., Thakur, J. K., and Kumar, S. (2013) Delineating groundwater potential zones in a hard-rock terrain using geospatial tools. Hydrological Sciences Journal, 58 (1), 1–11.     

Cartographically Wordy but not Necessarily Worthy

Abstract

A novel method called multidirectional visibility index (MVI) has been developed and verified. The MVI improves standard cartographic analytical shading with a number of enhancements to topographic detail and prominent structures, i.e. the portrayal of flat areas in lighter tones, the accentuation of morphologic edges, and the multiscale visualisation of morphologic terrain features. The procedure requires a digital elevation model (DEM) and involves the following steps: visibility mask computation; the respective multidirectional altering of the azimuth and elevation angle; the generation of continuous grid MVIs that indicate upper/lower views, quasi-slope, and relative relief; and an appropriate visualisation of the relevant MVI as a standalone technique or in combination with standard hill-shaded relief. The modelling parameters are robust and therefore highly adaptive to different landforms.     

组合法精化胶州市大地水准面

本文利用全球重力位模型、胶州市地面重力观测数据、胶州市GPS水准数据和数字地面模型(DTM),采用组合法应用移去-恢复技术计算剩余大地水准面,并与地球位模型计算的高程异常进行拟合,得到该地区重力似大地水准面,再和布测、计算得到的GPS/水准所构成的几何大地水准面拟合,利用多项式拟合完成系统改正,获得最终的大地水准面结果及相关的精度信息。     

多基线数字近景摄影平面地表测量可行性研究

以非量测性的数码相机高精度几何标定技术和多基线数字近景摄影测量技术为基础,本文设计出用于平面地表测量的可靠方法,经过理论研究和实验分析,验证了近景摄影测量用于平面地表测量的精度和可行性,为平面地表的地面近景摄影测量提供了便捷、可靠的途径,并为地面变形监测提供了有价值的参考方案。     

Validating the use of object-based image analysis to map commonly recognized landform features in the United States

ABSTRACT

The U.S. Geological Survey (USGS) National Geospatial Program (NGP) seeks to i) create semantically accessible terrain features from the pixel-based 3D Elevation Program (3DEP) data, and ii) enhance the usability of the USGS Geographic Names Information System (GNIS) by associating boundaries with GNIS features whose spatial representation is currently limited to 2D point locations. Geographic object-based image analysis (GEOBIA) was determined to be a promising method to approach both goals. An existing GEOBIA workflow was modified and the resulting segmented objects and terrain categories tested for a strategically chosen physiographic province in the mid-western US, the Ozark Plateaus. The chi-squared test of independence confirmed that there is significant overall spatial association between terrain categories of the GEOBIA and GNIS feature classes. Contingency table analysis also suggests strong category-specific associations between select GNIS and GEOBIA classes. However, 3D visual analysis revealed that GEOBIA objects resembled segmented regions more than they did individual landform objects, with their boundaries often failing to correspond to match what people would likely perceive as landforms. Still, objects derived through GEOBIA can provide initial baseline landscape divisions that can improve the efficiency of more specialized feature extraction methods.