地理信息系统发展趋势

本文根据国内外在地理信息系统方面的进展，就地理信息系统的科学概念、基本构成和它的以下一些发展趋势作了讨论：（1）地理信息系统是构成地理学日臻完善的技术体系的重要部分；（2）空间分析功能是系统研究和应用的主要目标；（3）系统最重要的技术问题是管理和存储大量空间数据的数据结构；（4）综合性的发展特色日益明显；（5）标准化和智能型的发展方向已引起关注。     

An alternative deduction of the hill-type surfaces of the spatial 3-body problem

In the present paper, inequalities stronger than Sundman's and the best possible zero velocity surfaces of the spatial 3-body problem first obtained by Saari (1987) are deduced using a modified version of the transformation developed by Zare (1976). The notion of inertia ellipsoid is used to show the equivalence of the present authors' result to that of Saari's.     

Geostatistical analysis of soil moisture measurements and remotely sensed data at different spatial scales

The European remote sensing satellite (ERS-2) synthetic aperture radar (SAR) data was used for temporal monitoring of soil moisture at Sukhothai, Thailand. Higher correlations were found between the observed soil moisture and the radar backscattering coefficient. The soil moisture distribution shows great variation in space and time due to its stochastic nature. In order to obtain a better understanding of the nature and causes of spatial variation of soil moisture, the extensive soil moisture measurements observed in Thailand and also remotely sensed ERS-2 SAR data were used for geostatistical analysis. The observed soil moisture shows seasonal variations with mean varying from 3.33 %v/v (dry season) to 33.44 %v/v (wet season). The spatial geostatistical structure also shows clear seasonal variations in the geostatistical characteristics such as range and sill. The sills vary from 1.00 (%v/v)² for the driest day to 107.57 (%v/v)² for one of the wet days. The range or the correlation lengths varies between 46.5 and 149.8 m for the wettest and driest periods. The nugget effect does not show strong seasonal pattern or trend but the dry periods usually have a smaller nugget effect than the wet periods. The spherical variogram model fits the sample variograms very well in the case of soil moisture observations while the exponential model fits those of the remotely sensed data. The ranges observed from the observed soil moisture data and remotely sensed data at the same resolution are very similar. Resolution degradation affects the geostatistical structure of the data by reducing the sills, and increasing the ranges.     

Soil erosion assessment and its verification using the Universal Soil Loss Equation and Geographic Information System: a case study at Boun,Korea

This study is aimed at the evaluation of the hazard of soil erosion and its verification at Boun, Korea, using a Geographic Information System (GIS) and remote sensing. Precipitation, topographic, soil, and land use data were collected, processed, and constructed into a spatial database using GIS and remote sensing data. Areas that had suffered soil erosion were analysed and mapped using the Universal Soil Loss Equation (USLE). The factors that influence soil erosion are rainfall erosivitiy (R) from the precipitation database, soil erodibility (K) from the soil database, slope length and steepness (LS) from the topographic database, and crop and management (C) and conservation supporting practices (P) from the land use database. Land use was classified from Landsat Thematic Mapper satellite images. The soil erosion map verified use of the landslide location data. Landslide locations were identified in the Boun area from interpretation of aerial photographs and field surveys.     

吉林西部盐碱化土地空间变化及防治措施

运用遥感、GIS等地学信息新技术手段获取了20世纪80年代及90年代中后期吉林西部地区盐碱化土地最新统计数据,通过空间分析,总结了该区近20a来盐碱化土地总体面积不断扩大、质量不断恶化及盐碱化发展具有阶段性时序变化的特点,最后给出了经济管理及生态工程等方面的防治措施。     

Models of sub-grid variability in numerical simulations of solute transport in heterogeneous porous formations: three-dimensional flow and effect of pore-scale dispersion

Modeling transport of contaminants in the earths subsurface relies on numerical solutions over grids with blocks larger than Darcys scale. The hydraulic conductivity is homogenized over the grid blocks and the plumes spreading is reduced as a consequence of the wiped-out variability. To compensate for this loss Rubin et al. (1999) proposed to augment mixing by block-effective dispersion coefficients, and Rubin et al. (2003) showed, by means of two dimensional simulations, how this concept can be applied in practice. In this paper, we present new solutions of the block-effective dispersion tensor for an axisymmetric exponential covariance model. In addition, we discuss the influence of pore-scale dispersion in both two- and three-dimensional applications.     

Eulerian spatial moments for solute transport in three-dimensional heterogeneous,dual-permeability media

A Eulerian analytical method is developed for nonreactive solute transport in heterogeneous, dual-permeability media where the hydraulic conductivities in fracture and matrix domains are both assumed to be stochastic processes. The analytical solution for the mean concentration is given explicitly in Fourier and Laplace transforms. Instead of using the fast fourier transform method to numerically invert the solution to real space (Hu et al., 2002), we apply the general relationship between spatial moments and concentration (Naff, 1990; Hu et al., 1997) to obtain the analytical solutions for the spatial moments up to the second for a pulse input of the solute. Owing to its accuracy and efficiency, the analytical method can be used to check the semi-analytical and Monte Carlo numerical methods before they are applied to more complicated studies. The analytical method can be also used during screening studies to identify the most significant transport parameters for further analysis. In this study, the analytical results have been compared with those obtained from the semi-analytical method (Hu et al., 2002) and the comparison shows that the semi-analytical method is robust. It is clearly shown from the analytical solution that the three factors, local dispersion, conductivity variation in each domain and velocity convection flow difference in the two domains, play different roles on the solute plume spreading in longitudinal and transverse directions. The calculation results also indicate that when the log-conductivity variance in matrix is 10 times less than its counterpart in fractures, it will hardly influence the solute transport, whether the conductivity field is matrix is treated as a homogeneous or random field.     

Spatial statistics of clustered data

Modern spatial statistics techniques are widely used to make predictions for natural processes that are continuously distributed over some convex domain. Implementation of these techniques often relies on the adequate estimation of certain spatial correlation functions such as the covariance and the variogram from the data sets available. This work studies the practical estimation of such spatial correlation functions in the case of clustered data. The coefficient of variation of the dimensionless spatial density of the point pattern of sample locations is suggested as a useful metric for degree of clusteredness of the clustered data set. We show that the common variogram estimator becomes increasingly unreliable with increasing coefficient of variation of the dimensionless spatial density of the point pattern of sample locations. Moreover, we present a modified form of the variogram estimator that incorporates declustering weights, and propose a scheme for estimating the declustering weights based on zones of proximity. Finally, insight is gained in terms of a numerical application of the common and modified methods on piezometric head data collected over an irregular network.Acknowledgments. This work has been supported by grants from the National Institute of Environmental Health Sciences (P42 ES05948-02), the Army Research Office (DAAG55-98-1-0289), and the National Aeronautics and Space Administration (60-00RFQ041). Some of the calculations conducted in support of this work were done on the SGI Origin 2400 at the North Carolina Supercomputing Center, RTP, NC.     

Pattern classification using tabu search to identify the spatial distribution of groundwater pumping

Pattern classification and Tabu Search are integrated to optimize the zonation and associated average groundwater pumping rates. A simulated problem analogous to the Choushui Creek Alluvial in Janghauh county of Taiwan is used to examine the proposed method. Three problems are tested including (1) optimizing zonation patterns with known pumping rates and number of zones, (2) optimizing pumping rates and zonation patterns with a predetermined number of zones, and (3) optimizing all pumping rates, number of zones, and zonation. The results indicate that the proposed method successfully identifies spatial patterns of groundwater pumping for all three cases. However, some initial zonations result only in local optimums. Thus, using more than one initial zonation to increase search diversification is recommended. Application to different problems such as the spatial distribution of hydraulic conductivity values and area weighting of rainfall stations, is encouraged.

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Resumen El patrón de clasificación y la búsqueda tabú están integrados para optimizar la zonificación y las tasas promedio de bombeo de aguas subterráneas asociadas. Se ha utilizado un área diseñada análoga al arroyo aluvial Choushui en la provincia Janghauh en Taiwan para examinar el método propuesto. Se han probado tres problemas que incluyen (1) la zonificación únicamente con las tasas de bombeo y número de zonas dadas, (2) tasa de bombeo y zonificación con un número predeterminado de zonas, y (3) todas las tasa de bombeo, número de zonas y zonificaciones. Los resultados indican que el método propuesto identifica exitosamente los patrones espaciales de bombeo de las aguas subterráneas en los tres casos. Sin embargo, Algunas zonificaciones iniciales solamente resultan en óptimos locales. Por esta razón se recomienda utilizar más de una zonificación inicial para incrementar la diversificación de la búsqueda. Se sugiere la aplicación a problemas diferentes tales como la distribución espacial de conductividades hidraúlicas y la ponderación de áreas de estaciones de monitoreo de precipitación.

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Résumé La classification des patrons et la recherche Tabu sont intégrés pour optimiser la zonation et la moyenne associée du taux de pompage de leau souterraine. Une région analogue à lalluvion du ruisseau Choushui de la région Janghauh en Taiwan a été recrée afin dexaminer la méthode proposée. Trois problèmes sont évalués, incluant loptimisation de (1) la zonation avec seulement un taux de pompage et un nombre de zones donnés, (2) le taux de pompage et la zonation avec un nombre prédéterminé de zones, et (3) tous les taux de pompage, nombre de zones et la zonation. Les résultats indiquent que la méthode proposée identifie avec succès les patrons de pompage de leau souterraine dans les trois cas. Toutefois, certaines zonations initiales résultent seulement en optimums locaux. Par conséquent, lutilisation de plus dune zonation initiale afin daugmenter la diversification de la recherche est recommandée. Lutilisation de la méthode est suggérée pour la résolution de différents problèmes tels que la distribution spatiale de la conductivité hydraulique et la pondération des stations de mesure de précipitations.

     

空间数据库引擎SDE的研究

利用大型关系数据库管理海量的GIS数据,由于空间数据的不定长,造成存储效率低下,此外,现有的SQL并不支持空间数据库检索,需要解决空间数据和DBMS之间数据的存储、读取、检索、管理等基本功能。探讨了空间数据库引擎(SDE)的概念、实质和特点,并对Arc SDE进行了研究,对MAPGIS7.0中的SDE做了简短描述。