地图目标移位的面目标变形约束及其处理(英文)     

毛建华  曾齐红  刘学锋 《地球空间信息科学学报》2009,12(2):117-122

The displacement operator is an important and still a hot topic in map generalization. In the generalization product, symbols must be unambiguous and easily perceived and readily understood, which makes space competition among features an important obstacle in the process of map objects displacement. Space conflict between objects, through propagation process, may be spread and more objects may drift into it. In order to maintain symbols equilibrium and spatial relationship between objects, some unimportant symbols or parts of symbols should be distorted under constraints according to visual graphic resolution thresholds to figure out space competition among map features. Three constraints including position, legibility and characteristics are important for the maintenance of symbols equilibrium and spatial relationship, which are discussed in this paper. The skeleton is introduced to represent area objects figure characteristic, in which an area object can be separated to parts hierarchically according to their importance in the construction. Then, the finite element method is applied to the map objects’ displacement and distortion, in which a strategy for the parameters of finite element method is discussed. Supported by the National Science Foundation of China (No.40401050), the Leading Academic Discipline Project of Shanghai Educational Committee (No.J50104), the Science Foundation of Shanghai Education Department (07ZZ09).  相似文献   

NUMERICAL EXPERIMENTS ON MULTI-LEVEL STATISTICAL ESTIMATION OF DYNAMIC BALANCE CONSTRAINTS IN GRAPES-3DVAR     

王瑞春  龚建东  张林  薛谌彬 《热带气象学报(英文版)》2015,21(4):417-427

This paper further explores the estimating and expressing of dynamic balance constraints using statistical methods in GRAPES-3DVAR (Version GM). Unlike the single-level scheme which only considers the coupling between mass and wind at one level, the multi-level scheme considers the coupling between their vertical profiles and calculates the balanced mass field at each layer using the rotational wind at all model levels. A reformed ridge regression method is used in the new scheme to avoid the multicollinearity problem and reduce the noises caused by unbalanced mesoscale disturbances. The results of numerical experiments show that the new scheme can get more reasonable vertical mass field, reduce the magnitude of the adjustment by the initialization, and improve the potential temperature analysis performance. Furthermore, the results of forecast verification in January (winter) and July (summer) both confirm that the new scheme can significantly improve the temperature forecast accuracy and bring slight positive effects to the pressure and wind forecast.  相似文献   

综合线面特征分布的点目标多尺度聚类方法     

余莉  甘淑  袁希平  杨明龙 《测绘学报》2015,44(10):1152-1159

考虑空间数据分布的复杂性与不连续性,提出了一种点目标聚类方法。算法利用全要素Voronoi图准确识别与表达点目标与线面实体的空间相关性;根据点目标位置分布特征计算面积阈值来控制聚类的粒度,同时以空间尺度变化下面积阈值的恒定作为判断尺度收敛的条件,实现点目标的多尺度划分,时间复杂度为O(nlogn)。经试验验证,聚类尺度随点目标分布特征自适应收敛,算法无须自定义参数,能够有效地发现受线面目标约束的任意形态点目标集群,对异常值处理稳健。  相似文献   

基于土地供需关系对北京城市拓展中土地资源约束条件的初步分析(英文)     

樊杰  张有坤 《资源与生态学报(英文版)》2012,(3):253-261

土地资源作为重要的自然环境载体,对城市发展既起到了支撑作用,同时也会制约城市的盲目扩张。本文以北京市为例,从供给与需求两方面,总结了北京城市发展的土地资源约束特征,初步测算了其城市空间的上限规模。一方面,分析了产业用地和生活居住用地等土地资源需求主导因素的特征和变化趋势,基于不同的土地利用效率情景,初步测算得出北京城市发展对土地资源的需求规模区间为[1596 km2,2846 km2]。另一方面通过分析北京地区农业空间、生态空间及其他用地空间的占用、消耗特征,测算得出不同情景下土地资源对北京城市发展的供给规模区间为[1673 km2,2821 km2]。可以看出,当前北京城市发展的土地需求明显大于供给。同时指出了未来北京城市拓展受到土地资源供给的总量约束、空间约束及城市功能定位决定的用地结构性约束等限制。最后尝试提出解决当前城市发展面临的资源环境瓶颈和城市病等问题的思路。  相似文献   

Assessing parameter identifiability for multiple performance criteria to constrain model parameters     

Björn Guse  Jens Kiesel  Matthias Pfannerstill  Nicola Fohrer 《水文科学杂志》2020,65(7):1158-1172

ABSTRACT

Reliable simulations of hydrological models require that model parameters are precisely identified. In constraining model parameters to small ranges, high parameter identifiability is achieved. In this study, it is investigated how precisely model parameters can be constrained in relation to a set of contrasting performance criteria. For this, model simulations with identical parameter samplings are carried out with a hydrological model (SWAT) applied to three contrasting catchments in Germany (lowland, mid-range mountains, alpine regions). Ten performance criteria including statistical metrics and signature measures are calculated for each model simulation. Based on the parameter identifiability that is computed separately for each performance criterion, model parameters are constrained to smaller ranges individually for each catchment. An iterative repetition of model simulations with successively constrained parameter ranges leads to more precise parameter identifiability and improves model performance. Based on these results, a more consistent handling of model parameters is achieved for model calibration.  相似文献   

攀西特色水果产业发展面临的限制、问题与建议     

沈茂英 《山地学报》2004,(Z1)

以攀西特色水果产业发展动态为主,分析指出技术和市场是约束该产业进一步发展壮大的双因子。其形成因素多,包括劳动者素质低下和家庭经营规模小、生产与市场之间的联系渠道不畅和农村技术服务体系发育滞后等;并提出促进特色水果产业壮大的建议。  相似文献   

A method for the interpolation of nonnegative functions with an application to contaminant load estimation     

A. M. Michalak  P. K. Kitanidis 《Stochastic Environmental Research and Risk Assessment (SERRA)》2005,19(1):8-23

The objective of this work is to extend kriging, a geostatistical interpolation method, to honor parameter nonnegativity. The new method uses a prior probability distribution based on reflected Brownian motion that enforces this constraint. The work presented in this paper focuses on interpolation problems where the unknown is a function of a single variable (e.g. time), and is developed both for the case with and without measurement error in the available data. The algorithms presented for conditional simulations are computationally efficient, particularly in the case with no measurement error. We present an application to the interpolation of dissolved arsenic concentration data from the North Fork of the Humboldt River, Nevada.  相似文献   

主成分估计与附加条件的参数平差     

宋力杰 《测绘工程》1997,6(1):24-27

证明了主成分估计实质上是附着条件的参数平差，并根据此性质结合算例分析了主成分估计的局限性，提出了改进方法。  相似文献   

Stress constraints and hydrofracturing stress data for the continental crust   总被引：1，自引：0，他引：1  

F. Rummel  G. Möhring-Erdmann  J. Baumgärtner 《Pure and Applied Geophysics》1986,124(4-5):875-895

Faulting and seismicity in the upper continental crust require considerable differential stresses. Application of experimentally developed friction, fracture and flow laws shows that high differential stresses can only exist in the uppermost crust. Direct hydraulic fracturing measurements in deep boreholes seem to support this rock mechanics conclusion. The experimental data base presently consists of approximately 500 hydrofrac tests conducted in about 100 boreholes at about 30 different geographical locations. To illustrate the variation of measured stresses with depth, the data are expressed as dimensionless horizontal stresses in the formS _H,h/S_v=(/z)+, whereS _v=gz Extrapolation of the experimental data to greater depth shows that the minor horizontal stress approaches the valueS _h/S_v=0.5 which limits friction on wet faults, and that the major horizontal stress approaches a value close toS _H/S_v=1 at rather shallow depth (5 to 10 km.). This limits faulting and seismicity in most of the upper crust to either strike-slip or normal faults. The lower boundary for seismicity is mainly dependent on tectonic strain accumulation and rock creep at the environmental conditions at depth.  相似文献   

A cross entropy method for flood frequency analysis     

N. C. Lind  H. P. Hong  V. Solana 《Stochastic Environmental Research and Risk Assessment (SERRA)》1989,3(3):191-202

The cross-entropy method with fractile constraints has been developed to estimate a random variable when the data are a set of independent observations of the variable. The method can claim several advantages over existing methods. It uses a reference distribution like the prior distribution in Bayesian analysis and likewise generates a posterior distribution.The method is of interest, in particular, because it satisfies two fundamental requirements for selfconsistency in the analysis of a probabilistic system based on data: a principle of invariance and a principle of data monotonicity.The method is applied to flood analysis. Robustness of the minimum cross-entropy method is compared with other methods: the methods of moments and the maximum likehood.  相似文献