On the influence of RF absorbing material on the GNSS position

Reflections of the GNSS signal around the antenna induce an error in the measurement of the satellite–receiver distance and therefore should be avoided as much as possible. One solution often used to mitigate these reflections is to apply radio frequency (RF) absorbing material to the antenna, its support or its site. Such material could however alter the antenna phase delay and, in turn, alter the position as calculated from the GNSS observations. We explain under which conditions the RF material will or will not alter the antenna phase delay, and hence in which conditions a re-calibration of the antenna is necessary after the installation of absorbing material. Furthermore, rules of thumb are given to install the material in such a way that re-calibration can be avoided. Some basic theory and measurements of the influence of RF material are reviewed. An application to a real life absorber setup similar to one of the International GNSS Service reference stations is then discussed, and the position offset due to the absorbing material is demonstrated. The topics discussed can serve station managers to limit effects of absorbing material and take precautions to avoid a position bias.     

Spectral identification of materials by reflectance spectral library search

Spectral library search is emerging as a viable approach for material identification and mapping by reusing spectral knowledge gained from hyperspectral remote sensing across space and time. The potential of retrieving meaningful spectral material identifications in the presence of reflectance of spectra of various material types and with various similarity metrics has been assessed in this study. Test reflectance spectra of various vegetation, minerals, soils and urban material types are identified by searching through the composite reflectance spectral library obtained by combining various institutional reflectance spectral libraries. The accuracy of material identifications under various conditions: (i) in the presence of identical, similar and dissimilar spectra; (ii) in the presence of only identical and dissimilar spectra; and (iii) in the presence of only dissimilar spectra has been assessed with several similarity metrics. Results indicate the possibility of obtaining 100% accurate material identifications by library search if the spectral library contains identical spectra. However, the presence of a large number of similar spectra, despite the presence of identical spectra, is found to increase false positives, thereby reducing the accuracy of retrievals to 82% at best. Further, the accuracy of material identifications in the presence of similar spectra is similarity metric-dependent and varied from about 52% (obtained from Binary Encoding) to 82% (obtained from Normalized Spectral Similarity Score). Overall, results support the possibility of using independent reflectance spectral libraries for material identification while calling for robust spectral similarity metrics.     

“岩浆期后矿床”的成矿原理与环形构造成矿

本文应用数学物理的方法对“岩浆期后矿床”的成矿原理和环形构造的控矿机制进行了研究,得出:“岩浆期后矿床”的成矿原理是:成矿物质是以早期气态分离的形式贮存于岩浆源顶部,“岩浆期后矿床”是由早期气态物质上升到地表后汇集而成;环形构造控制“岩浆期后矿床”,但是并不是所有环形构造都控制“岩浆期后矿床的形成,只有那些与早期气态物质上升高度相当的截面并由早期气态物质爆破形成的环形构造才有可能控制“岩浆期后矿床”的形成。     

基于已有资料的自动质检技术研究与实现

基础地理信息数据和专题资料数据等在测绘质检领域的应用越来越广,如果还是仅仅依靠质检人员使用这些资料数据进行手工检查已不能满足需要,因此,研发一套利用资料数据进行自动质检的软件系统是非常有必要的。本文通过分析当前常见的资料数据在质检领域的应用,以ArcGIS Engine为开发组件,设计实现了一个基于已有资料的自动化质检软件,该系统实现了道路编码属性项检查、行政区划代码检查等功能,提高了成果数据质检的效率。     

3D激光扫描应用于开采沉陷相似材料模型观测

根据开采沉陷相似材料模型实验的特点,采用了三维激光扫描仪对开采沉陷相似材料模型进行观测,得到了测点的拟合与建模两种三维坐标数据,分析了模型的下沉曲线,实现了用三维激光扫描仪对开采沉陷相似材料模型观测新方法的研究.     

Geomorphological units,their geohydrological characteristic and vertical electrical sounding response near Munger,Bihar

Geomorphological mapping through satellite remote sensing coupled with geophysical electrical resistivity survey (vertical electrical sounding) gives very useful information about spatial and depth-wise variation of aquifer’s material, respectively. The present study area broadly falls between the Ganga river and Kharagpur hills (a northern limit of Chotanagpur plateau). These hills are highly folded and consist of quartzites and phyllites of Precambrian age group In the study area, cover material above the basement is the product of weathering, colluvial and fluvial processes of different ages. Geomorphologically, study area has been categorised into different classes i.e. denudo-structural hill, buried pediment, younger alluvial plain, recent flood plain and older alluvial plain. Broadly these classes represent the general ground-water prospects, but in detail, possibility of variation in ground-water prospects cannot be ruled out. In alluvial plain (younger/older) main target for ground-water exploration is sandy horizon. Similarly in buried pediment the main target is coarse-grained weathered material with fractured basement, not the total general thickness of cover material on the basement. In the present paper, authors have tried to analyse the spatial distribution of geomorphic classes and depth-wise variation of aquifer material within the same class for determining the target horizon for further detailed investigation, using remote sensing and electrical sounding.     

论战场环境的区域特性

文章从战场景观、战场地域结构、战场物资潜力 3个方面研究战场环境的区域特性。阐述了景观、地域结构、物资潜力的概念内涵 ,并分析它们对战役活动的影响和制约。     

材质和倾角属性筛选的光伏屋顶提取

针对城市光伏屋顶类型多样致使样本不平衡,高空间分辨率卫星影像光伏屋顶提取问题,提出了一种材质和倾角属性筛选的方法.通过选取天津市南开区、红桥区、和平区、河东区卫星影像,利用标注于光伏屋顶的材质和倾角两种属性筛选出样本均衡的数据集,借助TensorFlow框架下集成的U-Net算法并合理设置参数,得到了光伏屋顶提取结果,...     

基于RS的林芝-加查段泥石流源地信息提取

为研究泥石流灾害对西藏雅鲁藏布江林芝-加查段沿线的影响与危害,基于遥感手段开展了林芝-加查段沿线泥石流源地物源及冰川水文信息特征的提取研究与分析。研究结果表明:林芝-加查段沿线泥石流源地物源分布具有不均匀性;源地冰川分布具有不平衡性;沿线泥石流源地的物源在冰川融水及冰川型泥石流过后更加发育,积累的松散物质更加丰富,导致泥石流源地物源进一步复活并产生大量新物源,从而使沿线泥石流发生频率增高,规模增大。     

Identification of groundwater prospective zones by using remote sensing and geoelectrical methods in and around saidnagar area,dakor block,jalaun district,uttar pradesh

The study area around Saidnagar falls in Bundelkhand granitic terrain forming buried pediplain (granite derived material). The occurrence and movement of groundwater is restricted to the unconsolidated material, weathered and fractured rock. For the selection of tube-well sites, geoelectrical resistivity investigations have been carried out at the sites which are found suitable based on remote sensing and hydrogeological studies. Twenty six Vertical Electrical Soundings (VES) have been carried out by using Schlumberger electrode configuration, which have brought out 3 and 4 layered sub-surface sections. The resistivity of water-bearing weathered/fractured rocks varies from 10 to 20 ohm m, with thickness ranging from 3.4 to 75.0 m. The depth to the basement is found ranging between 6.8 and 93.0 m The integrated studies have revealed that the northern part of the study area forms groundwater prospective zone, consisting of unconsolidated water-bearing weathered material, In the southern part of the study area, weathered layer is either thin or absent and the groundwater movement and storage is restricted to the weathered/fractured zone only. This zone extends down to a depth of 3.4 to 75.0 m and may yield sufficient amount of water since it gets recharged by direct infiltration due to precipitation and percolation through Nalas.     

基于Oracle Spatial的GIS数据一体化存储模型及在城镇地籍调查中的应用

本文主要围绕Oracle Spatial的对象-关系模型阐述了GIS数据一体化存储模型,并用具体实例分析了模型在城镇地籍调查中的应用。     

机助DTM计算体积的方法

利用全站仪测得的堆物表面离散特征点的”三维坐标（Ｘ，ｙ，ｈ），通过计算机自助排序的方法建立三角形覆盖网，再用平面切割的方法求定任一高度的面积，最后求得堆物体积。     

对地质灾害隐患早期识别相关问题的认识与思考

泥石流物源识别与计算是科学评估泥石流规模、危害程度以及综合治理的基础,而传统的地面调查和光学遥感手段难以有效识别山区植被茂密覆盖下的泥石流物源。机载激光雷达（light detection and ranging,LiDAR）技术能有效去除植被获取真实的地表形态,为泥石流物源的识别提供了新的解决方案。以九寨沟震区的日则沟泥石流为例,基于高分辨率机载LiDAR数据结合震前卫星影像,开展泥石流物源识别研究,根据物源所处位置和在山体阴影图像上的色彩及纹理差异,将物源分为崩滑物源、坡面物源和沟道物源,并建立各类型物源的机载LiDAR识别标志与遥感解译方法。共解译出日则沟泥石流物源155处,总面积达1.06 km²,占流域总面积的31.56%,在此基础上分析了各类型物源的发育分布规律。为泥石流物源的精确计算提供理论参考和数据支撑,进一步服务于九寨沟震区泥石流的防治与风险评价。

     

台海西岸电子沙盘系统的设计与实现

电子沙盘作为可交互操作的实时虚拟现实环境,是一种既具有传统沙盘的特点,又集成了多种高新技术的产品。首先分析了沙盘制作技术的变化与发展,即从传统的实物沙盘向现代的电子沙盘转变;然后提出了台海西岸电子沙盘制作的技术方案,并介绍了数据处理、地形模拟与要素匹配等关键技术;最后以数字高程模型（DEM）和卫星遥感图像为数据源．用MapGIS开发环境实现了该地区电子沙盘的制作。     

利用激光强度信息分类激光扫描测高数据

三维机载激光扫描测高数据中不仅含有每个激光脚点的位置和高程信息,而且越来越多的系统同时能提供激光脚点回波信号的强度信息。不同反射面介质对激光信号的反射特性不一样,用实测的数据对激光回波信号的强度信息进行统计标定,并基于标定结果,实现了联合激光强度信息和高程信息进行分类的算法,获得了较为满意的结果。     

Confirmation of soil physiographic units through soil mineralogy studies in Yamuna alluvial plain,India

A confirmatory study of soil physiographic units identified through aerial photo interpretation technique, in Yamuna alluvial plain, Haryana is presented here. The area under study is part of Yamuna alluvial plain in Sonepat district, Haryana. Shanwal and Malik (1980) studied and mapped this area (semi-detailed) on 1:25,000 scale through areial photo interpretation technique. The soil profile samples of major soil physiographic units of the area were fractionated into sand, silt and clay. Detail mineralagical studies were carried out through electron microscopic and X-ray diffractometer studies in order to know their nature and origin of the parent material. X-ray diffraction data shows that mineralogy of different fractions (Sand, silt and clay) of soils samples, of different physiographic units were similar except Lavee. In this area mica is the dominant day mineral in the soils followed by Kaolinite, chlorite, vermiculite and smectite in decreasing order of their abundances. The occurance of fibrous minerals in coarse clay and silt fraction of soil samples of Lavee physiographic unit is the interesting feature of this area. The presence of fibrous minerals indicates that this overlain material designated as natural Levee in this area is not the alluvium brought down by the river Yamuna but is aeolian material flown from adjoining deseret of Rajasthan and deposited as stabilized sand dune. The fibrous minerals have been reported earlier in the desert of Rajasthan.     

基于WebGIS的农资运输监控系统设计与实现

与工业品运输相比,农资运输的时效性更强,对运输环境的要求更为苛刻,如何对运输途中的车辆进行有效监控对农资企业来说尤为重要。本文根据农资运输的具体情况及特定要求,集成GPS,GIS,GPRS/3 G等技术,基于J 2 EE平台并采用Flex技术设计实现了WebGIS农资运输监控系统,实现了对农资运输过程的全程监控管理。目前,系统已在相关农资企业示范运行,为农资物流保障发挥了重要的作用。     

数字高程模型在坡耕地调查中的应用

以1:1万比例尺地形图(H-48-72-24)为例,采用地理信息系统软件Arc/Info数字化地形图生成数字高程模型,并通过DEM计算派生出坡度图,再结合土地利用现状图和相关资料,应用地理信息系统空间分析功能,自动提取坡耕地数据。整个过程主要由计算机进行处理,人工干预少,效率高。     

FBX三维模型自动转换为OBJ三维模型方法研究

本文研究实现了一种FBX三维模型自动转换为OBJ三维模型的方法,包括几何信息和材质信息的自动转换,所述方法包括获取数据、几何信息处理、材质信息处理、OBJ格式输出和材质库文件输出等步骤。     

武汉九峰地震台重力变化与地壳垂直形变分析

长期的重力变化和地壳形变观测是研究地下物质运动的重要手段。基于武汉九峰地震台2013—2020年的绝对重力和全球卫星导航系统（global navigation satellite system,GNSS）观测数据,计算了长期的重力与地壳垂直形变的变化趋势,并以1年、2年和3年的时间间隔分段,进行线性趋势拟合,分别获得不同时间段的绝对重力年变化率、地壳垂直形变速率以及对应的比值。研究结果表明,武汉九峰地震台长期的重力年变化率为0.479 9 μGal/a,地壳垂直形变速率为-1.2 mm/a, 两者的比值为-0.399 9 μGal/mm,与理论值存在一定的偏差,可能与该区域的地下水活动有关。将不同时间段的重力变化与地壳垂直形变的数据展布在一张图中,发现数据点离散分布在不同区域,由此可初步判断地下物质运动过程,为区域动力学机制解释提供参考。