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101.
Three‐dimensional architecture and hydrostratigraphy of cross‐cutting buried valleys using airborne electromagnetics,glaciated Central Lowlands,Nebraska, USA
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Buried valleys are characteristic features of glaciated landscapes, and their deposits host important aquifers worldwide. Understanding the stratigraphic architecture of these deposits is essential for protecting groundwater and interpreting sedimentary processes in subglacial and ice‐marginal environments. The relationships between depositional architecture, topography and hydrostratigraphy in dissected, pre‐Illinoian till sheets is poorly understood. Boreholes alone are inadequate to characterize the complex geology of buried valleys, but airborne electromagnetic surveys have proven useful for this purpose. A key question is whether the sedimentary architecture of buried valleys can be interpreted from airborne electromagnetic profiles. This study employs airborne electromagnetic resistivity profiles to interpret the three‐dimensional sedimentary architecture of cross‐cutting buried valleys in a ca 400 km2 area along the western margin of Laurentide glaciation in North America. A progenitor bedrock valley is succeeded by at least five generations of tunnel valleys that become progressively younger northward. Tunnel‐valley infills are highly variable, reflecting under‐filled and over‐filled conditions. Under‐filled tunnel valleys are expressed on the modern landscape and contain fine sediments that act as hydraulic barriers. Over‐filled tunnel valleys are not recognized in the modern landscape, but where they are present they form hydraulic windows between deep aquifer units and the land surface. The interpretation of tunnel‐valley genesis herein provides evidence of the relationships between depositional processes and glacial landforms in a dissected, pre‐Illinoian till sheet, and contributes to the understanding of the complex physical hydrology of glacial aquifers in general. 相似文献
102.
应用矩形辐射体航空伽玛辐射场理论,研究应用于复杂地形条件下的航空伽玛能谱资料的地形改正方法,并针对该方法进行验证. 本文利用航空物探测量过程中获得的DTM数据(达到了地形改正所需的地形起伏数据精度),应用矩形辐射体航空伽玛辐射场理论,根据地面辐射体与航空伽玛场分布之间的正演关系,对航空伽玛能谱解释方法的原理进行了正演分析和反演推导. 探索出一种按影响角进行地形改正的方法. 该方法特点是适合于任意飞行方式(缓地形和水平飞行均可)和任意地形条件航空伽玛能谱的逐点地形改正. 结果表明该地形改正方法能够基本消除航空伽玛能谱测量中的地形起伏产生的影响,经地形修正后的航空伽玛能谱异常能较正确地反映地面辐射体的真实情况. 相似文献
103.
Airborne infrared imagery is shown to provide preliminary evidence of surface thermal expressions associated with internal waves that become unstable and break over the continental shelf. These expressions include a narrow wave front that is warmer than the ambient; a wide, spatially intermittent ‘wake’ that is colder than the ambient; and ∼O (10 m) diameter surface-renewal ‘boils’ that populate the wake. These thermal signatures might be useful in assessing the spatial distribution and structure of breaking internal waves. 相似文献
104.
Ekaterina Batchvarova Xiaoming Cai Sven-Erik Gryning Douw Steyn 《Boundary-Layer Meteorology》1999,90(1):1-20
The purpose of this paper is to test the ability of two quite different models to simulate the combined spatial and temporal variability of the internal boundary layer in an area of complex terrain and coastline during one day. The simple applied slab model of Gryning and Batchvarova, and the Colorado State University Regional Atmospheric Modelling System (CSU-RAMS) are tested by comparison with data gathered during a field study (called Pacific '93) of photochemical pollution in the Lower Fraser Valley of British Columbia, Canada. The data utilised here are drawn from tethered balloon flights, free flying balloon ascents, and downlooking lidar operated from an aircraft flown at roughly 3500 m above sea level. Both models are found to represent the temporal and spatial development of the internal boundary-layer depth over the Lower Fraser Valley very well, and reproduce many of the finer details revealed by the measurements. 相似文献
105.
106.
建立地震灾害损失评估数据库是以ILWIS和PCARC/INFOGIS软件为工作平台。它能支持矢量格式的专题图件、栅格形成的遥感数据及关系表中的属性数据;它还可以实现矢量-栅格转换;而且数据库中的属性数据作为一个独立的关系表格存贮,并对应于其相关的空间单元。该数据库是以1976年唐山地震的航空遥感资料为基础,主要分3步进行。第一:建立地震区的基础地理数据库,包括:地理坐标、河流水系、县级行政区、公路、铁路和居民点;第二:应用航空遥感数据(航空影象)进行震区建筑物倒毁、生命线工程破坏及场地震害的分类分级,建立地震灾害数据库;第三:在GIS支持下,生成高烈度区包络线,并进行地震灾害据失评估。 相似文献
107.
108.
A comparison of the midlevel kinematic characteristics of a pair of supercell thunderstorms observed by airborne Doppler radar 总被引:1,自引:0,他引:1
The midlevel kinematic characteristics of two supercell thunderstorms observed during the Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX), one tornadic and the other nontornadic, are compared using airborne pseudo-dual-Doppler wind retrievals. The most significant difference between the two cases was that a midlevel rear-inflow jet was observed in the nontornadic supercell (12 May 1995), whereas such rear-to-front, storm-relative flow was absent at midlevels in the tornadic supercell (16 May 1995). The midlevel jet in the nontornadic supercell was located on the north flank of a prominent region of anticyclonic vertical vorticity. Some speculations are provided pertaining to the possible importance of the midlevel kinematic differences between the two storms. 相似文献
109.
高分辨率机载SAR影像空中三角测量模型 总被引:2,自引:0,他引:2
目前,我国西部地区近2000000km2的国土面积还缺乏相应比例尺的地形图,由于西部多云多雾天气条件的限制,采用高分辨率机载SAR遥感影像成为遥感技术测图实施中的重要数据源之一。同时,为了减少地面控制点的外业测量工作,研究如何获取足够数量及精度的控制点也成为当务之急。本文分析了高分辨率机载SAR影像空三应用的条件,并在测区稀少控制点的条件下,讨论DGPS/INS辅助机载SAR影像空三向量模型以及相应的数据处理方法,为机载SAR影像获取地面控制点的实际应用提供理论依据。 相似文献
110.
徕卡ADS 80数字航空相机采用POS/GPS精确导航定位技术进行航空摄影,通过对GPS差分数据进行常规布设控制点、少量布设控制点甚至无控制点的内业空三解算结果的对比分析,探讨外业像片控制点的布设方案对IMU/DGPS辅助航空摄影测量加密精度的影响,利用不同地形类别的加密数据,分析在保证成图精度的情况下如何减少外业工作量,降低生产成本,缩短生产周期。 相似文献