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排序方式: 共有141条查询结果,搜索用时 46 毫秒
41.
Nathaniel G. Plant Kacey L. Edwards James M. Kaihatu Jayaram Veeramony Larry Hsu K. Todd Holland 《Coastal Engineering》2009
Nearshore wave and flow model results are shown to exhibit a strong sensitivity to the resolution of the input bathymetry. In this analysis, bathymetric resolution was varied by applying smoothing filters to high-resolution survey data to produce a number of bathymetric grid surfaces. We demonstrate that the sensitivity of model-predicted wave height and flow to variations in bathymetric resolution had different characteristics. Wave height predictions were most sensitive to resolution of cross-shore variability associated with the structure of nearshore sandbars. Flow predictions were most sensitive to the resolution of intermediate scale alongshore variability associated with the prominent sandbar rhythmicity. Flow sensitivity increased in cases where a sandbar was closer to shore and shallower. Perhaps the most surprising implication of these results is that the interpolation and smoothing of bathymetric data could be optimized differently for the wave and flow models. We show that errors between observed and modeled flow and wave heights are well predicted by comparing model simulation results using progressively filtered bathymetry to results from the highest resolution simulation. The damage done by over smoothing or inadequate sampling can therefore be estimated using model simulations. We conclude that the ability to quantify prediction errors will be useful for supporting future data assimilation efforts that require this information. 相似文献
42.
精密卫星钟差两种插值方法的比较 总被引:1,自引:1,他引:0
介绍了两种GPS精密卫星钟差插值计算方法,采用实际数据进行了计算,与已知精密卫星钟差进行比较,结果显示线性插值方法略优于拉格朗日插值方法。 相似文献
43.
Suzette G. A. Flantua John H. van Boxel Henry Hooghiemstra John van Smaalen 《Climate Dynamics》2007,29(7-8):697-712
Climate changes affect the abundance, geographic extent, and floral composition of vegetation, which are reflected in the
pollen rain. Sediment cores taken from lakes and peat bogs can be analysed for their pollen content. The fossil pollen records
provide information on the temporal changes in climate and palaeo-environments. Although the complexity of the variables influencing
vegetation distribution requires a multi-dimensional approach, only a few research projects have used GIS to analyse pollen
data. This paper presents a new approach to palynological data analysis by combining GIS and spatial modelling. Eastern Colombia
was chosen as a study area owing to the migration of the forest–savanna boundary since the last glacial maximum, and the availability
of pollen records. Logistic regression has been used to identify the climatic variables that determine the distribution of
savanna and forest in eastern Colombia. These variables were used to create a predictive land-cover model, which was subsequently
implemented into a GIS to perform spatial analysis on the results. The palynological data from the study area were incorporated
into the GIS. Reconstructed maps of past vegetation distribution by interpolation showed a new approach of regional multi-site
data synthesis related to climatic parameters. The logistic regression model resulted in a map with 85.7% predictive accuracy,
which is considered useful for the reconstruction of future and past land-cover distributions. The suitability of palynological
GIS application depends on the number of pollen sites, the distribution of the pollen sites over the area of interest, and
the degree of overlap of the age ranges of the pollen records. 相似文献
44.
We describe an objective method for evaluating the spatial distribution of water equivalents of the snow cover within a small catchment. Regression analysis is used to quantify the relationship between elevation, presence or absence of forest, and potential direct solar radiation as independent variables and water equivalent as measured at a number of sites. First, this regression relationship is used to interpolate water equivalent data all over the basin area. Then we interpolate the residuals of the regression using a geostatistical approach. Superimposing the results obtained by interpolating the regression relationship and the interpolated residuals eventually yields the water equivalent distribution over the test area. The advantages of the interpolation method used lie in the optimal (effective, unbiased) estimation of the interpolated values as well as in the possibility to quantify the associated estimation variances. 相似文献
45.
46.
医学图像三维重建的插值方法研究 总被引:9,自引:0,他引:9
本文从算法的形成过程、基本原理和步骤、适用范围和局限性、以及可能的改进方法等对现有三维重建的插值方法作了评述。探讨了各种插值方法之间的内在联系,分析了存在局限性的本质原因。对插值问题的进一步研究方向提出了看法。 相似文献
47.
48.
Understanding and quantifying sediment load is important in catchments draining highly erodible materials that eventually contribute to siltation of downstream reservoirs. Within this context, the suspended sediment transport and its temporal dynamics have been studied in the River Isábena (445 km2, south-central Pyrenees, Ebro basin) by means of direct sampling and turbidity recording during a 3-year dry period. The average flood-suspended sediment concentration was 8 g l− 1, with maximum instantaneous values above 350 g l− 1. The high scatter between discharge and suspended sediment concentrations (up to five orders of magnitude) has not permitted the use of rating curve methods to estimate the total load. Interpolation techniques yielded a mean annual sediment load of 184,253 t y− 1 for the study period, with a specific yield of 414 t km− 2 y− 1. This value resembles those reported for small torrents in nearby mountainous environments and is the result of the high connectivity between the badland source areas and stream courses, a fact that maximises sediment conveyance through the catchment. Floods dominated the sediment transport and yield. However, sediment transport was more constant through time than that observed in Mediterranean counterparts; this can be attributed to the role of base flows that entrain fine sediment temporarily stored in the channel and force the river to carry high sediment concentrations (i.e., generally in the order of 0.5 g l− 1), even under minimum flow conditions. 相似文献
49.
秦岭主脊区年降水量空间插值最优方法研究 总被引:1,自引:0,他引:1
利用ARCGIS软件,以研究区多年平均年降水量为数据源,开展以下研究:(1)采用反距离权重法、普通(泛)克里金法、样条函数法和趋势面法进行直接内插。(2)利用降水量随海拔递增率,再次利用以上方法进行插值。(3)分析站点数量的变化对插值精度的影响。(4)分析插值空间尺度变化对插值精度的影响。针对插值结果,使用交叉验证法来评估插值方法的优劣,旨在找出研究区年降水量空间插值的最优方法。结果表明:(1)研究区多年降水量与纬度呈现出很好的负相关,与其他各地理环境因子相关性很差或无相关性。(2)考虑降水随海拔的递增率后,研究区南坡西段和研究区海拔<600 m和>800 m的大部分观测站的空间内插精度得到有效提高,其它区域以及其它海拔区间的插值精度反而降低,因此使用单一线性数据作为整个研究区降水随海拔的变化率不够科学和严谨。(3)在缺少研究区不同剖面降水观测资料的情况下,权重为0.001 的正规则样条函数法是最优插值方法。(4)像元尺度在50~1 000 m间的变化对降水插值的不确定影响甚微;插值精度与选取的插值点个数无明显相关性,当站点个数为20个时,插值精度最高。 相似文献
50.
以1965—1999年河北省逐月平均气温为研究对象,采用一元线性回归法和IDW(Inverse Distance Weighted)相结合的方法,将温度插值到河北省整个区域,绘制河北省温度空间分布图,实现河北省年内各月平均气温空间填图;同时,分析了河北省冬季和夏季各月的月平均温度的误差精度。结果表明:插值的结果与观测值的相关系数(R)在12个月均大于0.82,显示插值方法具有较好的模拟精度,可用于气温的空间插值和特征分析。 相似文献