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去过北京的人,几乎都欣赏过天安门前那对高大的华表。这对用汉白玉雕刻而成的华表,挺拔笔直的柱身上雕有螭龙流云纹饰,上部横插一块石片,石片上有浮雕的祥云,仿佛高大的柱身直插云问。捶顶承露盘中,蹲坐着一头别致的怪兽。 相似文献
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目前,遥感技术广泛应用于国民经济各部门和许多科学领域,我们运用这一新技术进行河南全省国土资源的调查研究,获得了可喜的成果。这项研究得到了河南省人民政府和国家计委的极大关注和支持,并列为省“七五”期间重点攻关项目之一。为保证任务的顺利完成,采取了协作攻关的办法,由省计经委和省科委牵头成立了“河南遥感技术协作委员会”,并交省计经委国土办具体组织实施。先后调动和组织了22个科研机构、大专院校和有关厅局100余名利技工作者参与攻关研究。从1984年10月正式开题,到1988年9月结束,历时四年,圆满地完成了任务,取得了较为丰硕的成果。 相似文献
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内蒙古自治区位于祖国北部边疆,地域辽阔,横跨祖国“三北”(东北、华北、西北)地区,国土面积118．3万平方公里,约占全国总面积的八分之一。内蒙古跨越华北地台与天山-内蒙-兴安地槽褶皱区两个一级大地构造单元,区内地层发育较全,地质构造复杂多样,各期岩浆活动频繁,成矿地质条件优越。经过半个多世纪的地质勘查工作,已查明自治区境内矿产资源比较丰富,而且具有矿种多、分布广的特点,有些资源在国内乃至世界上都占有重要地位。在国家实施西部大开发和振兴东北老工业基地的宏伟战略中,自治区矿产资源必将发挥重要作用。 相似文献
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教学不是教书,而是教学生学,教学生自己学,教学生从"学会"提升到"会学"和"能学"。聪明的学生之所以聪明,在于他们善于独立掌握科学的学习方法;高明的老师之所以高明,在于他们善于放开学生的手脚,引导学生学会学习。下面的这则事例是笔者亲历所为,今记述下来,以资各位地理同行在参考之余能有所启迪。半年前,到学校视导时与一位高三学生谈心,得知其地理学得不好,感知她很郁闷。她说,老师,地理好难学啊!何以见得呢?我问道。不是吗,大家都说地理是文科中的理科?她反问道。是的,有这种说法,我答道,地理你最怕做什么题?她说,我最怕综合题。你语文学得怎么样?我又问道。语文是我学得最好的,她无不 相似文献
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安徽省滁州市地名设标工作通过市场运作取得了好的效果,既筹措了大量资金,又推动了设标进度,为城市基础设施增添了亮点。目前全市筹措社会资金260多万元,政府财政补贴50万元。其中广告位招租筹措设标经费140万元,制作了A级路牌近500块,完成了滁州市和定远县、来安县等城镇主要街、路标牌的设置任务。筹措单位楼门牌的设置经费120万元,完成了84个居民区、6个商业集中区和11个单位办公区楼、门牌、单元牌和户室牌的设置任务。利用财政补贴经费初步完成了部分次要路段和巷的标牌设置任务,完成了部分下岗职工和无业人员住户牌的设置任务。 相似文献
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LiCl的Pitzer参数的优化 总被引：2，自引：6，他引：2
由于锂盐的重要性和氯化锂在电解质中的特殊性，ＬｉＣｌ和Ｃｉ２ＳＯ４的热力学问题一直被化学家所重视。Ｐｉｔｚｅｒ在其关于电解质的系列论文中给出的ＬｉＣｌ参数，适用的最大浓度仅为６ｍ。１９８８年Ｈｅｅ—Ｔａ１Ｋｉｍ等给出了适用于浓度直达饱和的参数。本文根据多年来我们对含锂盐体系的研究结果，经多种处理获得了ＬｉＣｌ和Ｌｉ２ＳＯ４的新Ｐｉｔａｅｒ参数。发现对于０—６ｍ和６ｍ一饱和不同浓度范围，ＬｉＣｌ的Ｐｉｔｚｅｒ参数截然不同。所获得的参数对于溶解度计算特别有意义。作者还从ＬｉＣｌ溶液的结构讨论了造成参数不同的原因。 相似文献
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南极旅游是人类和平利用南极的方式之一。南极旅游始于上世纪五十年代末。在此后的半个多世纪中,南极旅游呈稳步发展趋势,游客人数明显上升,游览路线日渐成熟,交通方式逐步固化,多国经营者合作模式不断完善。与此同时,《南极条约》体系对南极旅游的环保规制也在不断加强。中国涉足南极旅游的时间较短,目前每年只有二三百人员赴南极旅游。鉴于南极旅游有利于提高人们欣赏自然景观、提高环保意识,有利于增进国际文化交流与环保合作,有利于促进产业结构的调整和优化,因此,建议中国加强对南极旅游问题的研究,尽快制订相应的法律法规,使南极旅游的开展与管理有法可依,有序进行;加快对国际规则的熟悉,加快与国际惯例的接轨;按照商业的发展规律去推动南极旅游业。 相似文献
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TANGGuoan ZHAOMudan LITianwen LIUYongmei ZHANGTing 《地理学报(英文版)》2003,13(4):387-394
Slope is one of the crucial terrain variables in spatial analysis and land use planning, especially in the Loess Plateau area of China which is suffering from serious soil erosion. DEM based slope extracting method has been widely accepted and applied in practice. However slope accuracy derived from this method usually does not match with its popularity. A quantitative simulation to slope data uncertainty is important not only theoretically but also necessarily to applications. This paper focuses on how resolution and terrain complexity impact on the accuracy of mean slope extracted from DEMs of different resolutions in the Loess Plateau of China. Six typical geomorphologic areas are selected as test areas, representing different terrain types from smooth to rough. Their DEMs are produced from digitizing contours of 1:10,000 scale topographic maps. Field survey results show that 5 m should be the most suitable grid size for representing slope in the Loess Plateau area. Comparative and math-simulation methodology was employed for data processing and analysis. A linear correlativity between mean slope and DEM resolution was found at all test areas, but their regression coefficients related closely with the terrain complexity of the test areas. If taking stream channel density to represent terrain complexity, mean slope error could be regressed against DEM resolution (X) and stream channel density (S) at 8 resolution levels and expressed as(0.0015S2 0.031S-0.0325)X-0.0045S2-0.155S 0.1625, with a R2 value of over 0.98. Practical tests also show an effective result of this model in applications. The new development methodology applied in this study should be helpful to similar researches in spatial data uncertainty investigation. 相似文献
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Slope is one of the crucial terrain variables in spatial analysis and land use planning, especially in the Loess Plateau area of China which is suffering from serious soil erosion. DEM based slope extracting method has been widely accepted and applied in practice. However slope accuracy derived from this method usually does not match with its popularity. A quantitative simulation to slope data uncertainty is important not only theoretically but also necessarily to applications. This paper focuses on how resolution and terrain complexity impact on the accuracy of mean slope extracted from DEMs of different resolutions in the Loess Plateau of China. Six typical geomorphologic areas are selected as test areas, representing different terrain types from smooth to rough. Their DEMs are produced from digitizing contours of 1:10,000 scale topographic maps. Field survey results show that 5 m should be the most suitable grid size for representing slope in the Loess Plateau area. Comparative and math-simulation methodology was employed for data processing and analysis. A linear correlativity between mean slope and DEM resolution was found at all test areas, but their regression coefficients related closely with the terrain complexity of the test areas. If taking stream channel density to represent terrain complexity, mean slope error could be regressed against DEM resolution (X) and stream channel density (S) at 8 resolution levels and expressed as (0.0015S2+0.031S-0.0325)X-0.0045S2-0.155S+0.1625, with a R2 value of over 0.98. Practical tests also show an effective result of this model in applications. The new development methodology applied in this study should be helpful to similar researches in spatial data uncertainty investigation. 相似文献
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DEM提取黄土高原地面坡度的不确定性 总被引：72，自引：0，他引：72
选择陕北黄土高原6个典型地貌类型区为试验样区,采用野外实测及高精度的1:1万比例尺DEM为基准数据,研究栅格分辨率及地形粗糙度对DEM所提取地面平均坡度精度的影响。结果显示,对于1:1万比例尺DEM,5 m是保证该地区地形描述精度的理想分辨率尺度;多要素逐步回归模拟的方法进一步揭示了DEM所提取的地面平均坡度误差E与栅格分辨率X以及地形起伏的代表性因子-沟壑密度S之间存在的量化关系为E = (0.0015S2+0.031S-0.0325)X-0.0045S2-0.155S+0.1625,该结果也为确定适用的DEM分辨率提供了理论依据。 相似文献
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T. Edwin Chow Michael E. Hodgson 《International journal of geographical information science》2013,27(10):1277-1295
This paper examines the effect of scale (exhibited by spatial sampling) in modeling mean slope from lidar data using two representations of scale: lidar posting density (i.e. post‐spacing) and DEM resolution (i.e. cell size). The study areas selected include six small (i.e. approximately 3 km2) urban drainage basins in Richland County, SC, USA, which share similar hydrologic characteristics. This research spatially sampled an airborne lidar dataset collected in 2000 at a 2 m nominal posting density to simulate lidar posting density at various post‐spacings, from 2 m through 10 m. DEMs were created from the lidar observations at a corresponding cell size using spatial interpolation. Finally, using these DEMs, a sensitivity analysis between modeled terrain slope and lidar post‐spacing was conducted. Results of the sensitivity analyses showed that the deviation between mean slope and modeled mean slope decreases with finer posting density and DEM resolution. The relationship of mean slope with varying cell sizes and post‐spacing suggests a linear and a logarithmic function, respectively, for all study areas. More importantly, cell size has a greater effect on mean slope than lidar posting density. Implications of these results for lumped hydrologic modeling are then postulated. 相似文献
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1 Introduction Automated extraction of drainage features from DEMs is an effective alternative to the tedious manual mapping from topographic maps. The derived hydrologic characteristics include stream-channel networks, delineation of catchment boundaries, catchment area, catchment length, stream-channel long profiles and stream order etc. Other important characteristics of river catchments, such as the stream-channel density, stream-channel bifurcation ratios, stream-channel order, number… 相似文献
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Hydrologic data derived from digital elevation models (DEM) has been regarded as an effective method in the spatial analysis of geographical information systems (GIS). However, both DEM resolution and terrain complexity has impacts on the accuracy of hydrologic derivatives. In this study, a multi-resolution and multi-relief comparative approach was used as a major methodology to investigate the accuracy of hydrologic data derived from DEMs. The experiment reveals that DEM terrain representation error affects the accuracy of DEM hydrological derivatives (drainage networks and watershed etc.). Coarser DEM resolutions can usually cause worse results. However, uncertain result commonly exists in this calculation. The derivative errors can be found closely related with DEM vertical resolution and terrain roughness. DEM vertical resolution can be found closely related with the accuracy of DEM hydrological derivatives, especially in the smooth plain area. If the mean slope is less than 4 degrees, the derived hydrologic data are usually unreliable. This result may be helpful in estimating the accuracy of the hydrologic derivatives and determining the DEM resolution that is appropriate to the accuracy requirement of a particular user. By applying a threshold value to subset the cells of a higher accumulation flow, a stream network of a specific network density can be extracted. Some very important geomorphologic characteristics, e.g., shallow and deep gullies, can be separately extracted by means of adjusting the threshold value. However, such a flow accumulationbased processing method can not correctly derive those streams that pass through the working area because it is hard to accumulate enough flow direction values to express the stream channels at the stream's entrance area. Consequently, errors will definitely occur at the stream’s entrance area. In addition, erroneous derivatives can also be found in deriving some particular rivers, e.g., perched (hanging up) rivers, anastomosing rivers and braided rivers. Therefore, more work should be done to develop and perfect the algorithms. 相似文献
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DEM地形信息量的准确度量是判定DEM数据应用适宜性与限制性关键。以黄土丘陵沟壑区DEM及其派生的坡度、坡向DTM为例进行实验,研究子集划分与分级数对DEM信息量估算精度的影响。结果表明,DEM地形信息量是实际地形信息和子集划分策略共同作用的结果,现有DEM信息量计算存在不确定性,DEM子集划分算法和分级数的选择直接影响DEM信息量的计算结果。文章借助最大熵定理的基本思路构建DEM地形信息量分级判定模型,可客观获得连续型栅格地形数据在信息量计算上最优分级,为有效估算DEM地形信息量提供科学依据。 相似文献
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地形信息对确定DEM适宜分辨率的影响 总被引：2，自引：0，他引：2
分辨率会直接影响基于栅格数字高程模型（DEM）的数字地形分析结果,因此在实际应用中,需要选择适宜的DEM分辨率。目前采取的基本方法,基于某种地形信息定量刻画尺度效应曲线,从而确定DEM适宜分辨率,但对于采用不同地形信息时所产生的影响尚缺乏研究。本文针对该方法中通常采用的坡度、剖面曲率、水平曲率等3 种地形信息,每种地形信息提取时,分别使用两种不同的常用算法,在3 个不同地形特征的研究区中,逐一计算其在不同分辨率下的局部方差均值,以刻画尺度效应曲线,确定相应的DEM适宜分辨率,并进行对比分析。结果表明：① 采用剖面曲率或水平曲率所得适宜分辨率结果基本相同,但采用坡度所得出的适宜分辨率结果则有明显差别,后者所得的适宜分辨率更粗;② 采用不同地形信息时,越是在平缓地形为主的研究区,所得的适宜分辨率结果越相近,在复合地形特征的研究区所得到的适宜分辨率区间均明显较宽;③ 地形属性计算时所用的算法对适宜分辨率结果的影响不明显。 相似文献
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A study on DEM-derived primary topographic attributes for hydrologic applications: Sensitivity to elevation data resolution 总被引：1，自引：0，他引：1
Primary topographic attributes play a critical role in determining watershed hydrologic characteristics for water resources modeling with raster-based digital elevation models (DEM). The effects of DEM resolution on a set of important topographic derivatives are examined in this study, including slope, upslope contributing area, flow length and watershed area. The focus of the study is on how sensitive each of the attributes is to the resolution uncertainty by considering the effects of overall terrain gradient and bias from resampling. Two case study watersheds of different gradient patterns are used with their 10 m USGS DEMs. A series of DEMs up to 200 m grid size are produced from the base DEMs using three commonly used resampling methods. All the terrain variables tested vary with the grid size change. It is found that slope angles decrease and contributing area values increase constantly as DEMs are aggregated progressively to coarser resolutions. No systematic trend is observed for corresponding changes of flow path and watershed area. The analysis also suggests that gradient profile of the watershed presents an important factor for the examined sensitivities to DEM resolution. 相似文献