Effect of Contour Intervals and Grid Cell Size on the Accuracy of DEMs and Slope Derivatives   总被引：5，自引：0，他引：5  

Feras M Ziadat 《Transactions in GIS》2007,11(1):67-81

Digital Elevation Models (DEMs) are indispensable tools in many environmental and natural resource applications. DEMs are frequently derived from contour lines. The accuracy of such DEMs depends on different factors. This research investigates the effect of sampling density used to derive contours, vertical interval between contours (spacing), grid cell size of the DEM (resolution), terrain complexity, and spatial filtering on the accuracy of the DEM and the slope derivative. The study indicated different alternatives to achieve an acceptable accuracy depending on the contour interval, the DEM resolution and the complexity of the terrain. The effect of these factors on the accuracy of the DEM and the slope derivative was quantified using models that determine the level of accuracy (RMSE). The implementation of the models will guide users to select the best combination to improve the results in areas with similar topography. For areas with variable terrain complexity, the suggestion is to generate DEMs and slope at a suitable resolution for each terrain separately and then to merge the results to produce one final layer for the whole area. This will provide accurate estimates of elevation and slope, and subsequently improve the analyses that rely on these digital derivatives.  相似文献   

Seasonal cycle of topography in the Bohai Sea and Yellow Sea and its relationships with atmospheric forcing and oceanic adjustment based on altimetry data   总被引：1，自引：0，他引：1  

王凡林鹏飞  陈永利唐晓晖 《中国海洋湖沼学报》2004,22(3):256-264

Seasonal cycle is the most significant signals of topography and circulation in the Bohai Sea (BS)and Yellow Sea (YS) forced by prevailing monsoon and is still poorly understood due to lack of data in their interiors. In the present study, seasonal cycles of topography in the BS and YS and its relationship with atmospheric forcing and oceanic adjustment were examined and discussed using TOPEX/Poseidon and ERS-I/2 Sea Level Anomalies (SLA) data. Analyses revealed complicated seasonal cycles of topography composed mainly of 2 REOF modes, the winter-summer mode (WlM) and spring-autumn mode (SAM). The WlM with action center in the BS displayed peak and southward pressure gradient in July, and valley and northward pressure gradient in January, which is obviously the direct response to monsoon with about l-month response time. The SAM with action center in the western south YS displayed peak and northward pressure gradient in October and valley and southward pressure gradient in April. After the mature period of monsoon, the action center in the BS becam eweakened while that in the western south YS became strengthened because of regional convergence or divergence induced by seasonal variations of the Taiwan Warm Current and Yellow Sea Coastal Current. The direct response of topography to monsoon resulted in the WIM, while oceanic adjustment of topography played an important role in the forming of the SAM.  相似文献   

LITH5.0: a revised crustal model for Canada based on Lithoprobe results     

H. K. C. Perry  D. W. S. Eaton  A. M. Forte 《Geophysical Journal International》2002,150(1):285-294

  相似文献   

Gravity-field improvement in the Mediterranean Sea by estimating the bottom topography using collocation   总被引：4，自引：0，他引：4  

D. Arabelos  I. N. Tziavos 《Journal of Geodesy》1998,72(3):136-143

The contribution of bathymetry to the prediction of quantities related to the gravity field (e.g., gravity anomalies, geoid heights) is discussed in an extended test area of the central Mediterranean Sea. Sea gravity anomalies and a priori statistical characteristics of depths are used in a least-squares collocation procedure in order to produce new depths, giving a better smoothing of the gravity field when using a remove-restore procedure. The effect of the bottom topography on gravity-field modeling is studied using both the original and the new depths through a residual terrain modeling reduction. The numerical tests show a considerable smoothing of the sea gravity anomalies and the available altimeter heights when the new depth information is taken into account according to the covariance analysis performed. Moreover, geoid heights are computed by combining the sea gravity anomalies either with the original depths or with the new ones, using as a reference surface the OSU91A geopotential model. Comparing the computed geoid heights with adjusted altimeter sea-surface heights (SSHs), better results are obtained when subtracting the attraction of the new depth information. Similar results are obtained when predicting gravity anomalies from altimeter SSHs where the terrain effect on altimetry is based on the new bottom topography. Received: 10 September 1996 / Accepted: 4 August 1997  相似文献   

Stable Nocturnal Boundary Layers: A Comparison of One-Dimensional and Large-Eddy Simulation Models   总被引：1，自引：1，他引：0  

S. Galmarini 《Boundary-Layer Meteorology》1998,88(2):181-210

  相似文献   

正压模式中大地形作用下的低频波   总被引：1，自引：0，他引：1  

付遵涛  王树涛 《高原气象》1998,17(3):223-230

利用包含大地形和常数纬向基本气流的正压模式方程组,研究了大地形对低频波激发的作用,结果表明：起作用的地形因子主要是地形的最大高度和地形坡度,地形最大高度的作用主要是使Ｒｏｓｓｂｙ波趋向低频,而地形坡度的作用主要是对Ｒｏｓｓｂｙ波的稳定性决定作用。同时,适当地形坡度也可导致低频波的形成。  相似文献   

不同地形下辐射收支各分量的差异与变化   总被引：12，自引：0，他引：12  

傅抱璞 《大气科学》1998,22(2):178-190

给出了确定山区辐射收支各分量的方法,并根据计算结果分析了在不同纬度和季节各种地形下辐射收支各分量的差异及其随坡地倾角或谷地周围地形遮蔽角的变化规律。  相似文献   

可持续发展观与传统发展观的反思与对比   总被引：1，自引：0，他引：1  

任建兰 《地理科学进展》1998,17(3):69-73

本文论述了两种发展观产生的历史背景,在总结传统发展观的基础上,重点分析了可持续发展观的深层和表象特征,提出了人类推动社会持续发展所应坚持的理论与实践准则。  相似文献   

中国古村落景观的空间意象研究^*   总被引：53，自引：6，他引：47  

刘沛林  董双双 《地理研究》1998,17(1):31-38

引入“意象”(image)的概念,借助从感觉形式研究聚落空间形象的方法,对中国古村落景观的多维空间立体图象作了初步研究。文章把中国古村落景观的基本意象概括为:①山水意象,②生态意象,③宗族意象,④趋吉意象等四个方面;并对不同地域古村落景观意象的差异作了比较。  相似文献   

湖北强降水频次时空特征及基于GWR模型的地形关系分析     

谌伟  刘佩廷  徐枝芳  徐迎春  杨海鹏 《热带气象学报》2022,38(2):216-226

利用1983—2017年湖北省汛期74个国家气象站逐小时降水数据,按长、短历时强降水事件分类研究强降水频次的时空特征,并运用普通最小二乘法(OLS)、地理加权回归(GWR)方法定量探讨强降水频次与地形因子之间的关系。(1) 湖北汛期长、短历时强降水年频次周期变化明显,年代际变化(≥10 a)存在1个主振荡模态,年代际以下尺度(＜10 a)存在2个主振荡模态。(2) 长历时强降水旬频次在梅雨期达到顶峰,盛夏期减少,而短历时则在梅雨结束后的7月中旬出现跃升;长、短历时强降水频次日变化曲线都为单峰结构。(3) 湖北长、短历时强降水高频次站点多出现在地面存在准常定中尺度辐合线或涡旋的特定地形条件下。(4) 地理加权回归较传统普通最小二乘法显著提高了强降水频次与海拔高度、坡度的拟合效果。结合拟合系数显著性检验分析,地理加权回归不适用于样本偏少、站点稀疏的鄂西山地,更适用于多中小尺度地形的湖北中东部。(5) 地理加权回归模型中,海拔高度与长历时强降水频次在大别山东麓西侧正相关最大,在大别山西麓南侧负相关最大,坡度则正相反;海拔高度、坡度对短历时强降水频次的最大影响在大别山东麓西侧以及沿长江干流的低洼城市带武汉-黄石地区,武汉站分别为-0.20次/米、6.43次/度,这里地形坡度影响远超海拔高度。   相似文献