A visual programming language for spatial modelling in GIS

An integration between a visual programming environment and GIS has been developed to create and run spatial models. The visual programming environment provides graphical objects to create flowchart-like models of spatial phenomena using GIS data. The integrated system is object-oriented and designed to lessen the technical burdens of GIS programming. The system capabilities are demonstrated using a hydrological model example, and the model execution speed is compared with an equivalent model implementation in a traditional raster-based modelling system.     

A GIS FOR THE ANTARCTIC SPECIALLY MANAGED AREA OF ADMIRALTY BAY,KING GEORGE ISLAND,ANTARCTICA

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GIS 优化 SRM 储流函数模型变量与参数方法研究

水文模型的结构确定后,模型参数的选择对水文模型整体性能和水文预报结果的好坏有着至关重要的影响。为使得模型的输出值能够尽可能地接近实际值,文中结合数字高程模型(DEM)和流域地质资料,使用GIS方法分别从优化数据源和加入地质因素影响分析优化模型参数两方面入手,对SRM储流函数模型进行优化,并以北海道沙流川流域为例对上述方法进行检验,结果说明了方法的可行性。     

中国兰坪地区铜﹑铅﹑锌矿潜在分布的GIS预测模型(英文)

Mineral resource potential mapping is a complex analytical process,which requires the consideration and the inte-gration of a number of spatial evidences like geological,geomorphological,and wall rock alteration.The aim of this paper is to establish mineral exploration model for copper,lead,and zinc in Lanping basin area using the capability of analytical tools of Geographic Information System(GIS) and remote sensing data to generate maps showing favorable mineralized area.The geo-exploration dataset used f...     

Groundwater potential modelling using remote sensing and GIS: a case study of the Al Dhaid area,United Arab Emirates

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) DEM and LANDSAT images of spatial resolution 30?m were used to construct groundwater potential zones (GPZ) map by integrating geological fractures, drainage network, slope and relief, and convergence index maps of the study area. Weight and score of each map were developed according to their level of contribution toward groundwater accumulation and spatial distribution of groundwater wells. The area that has very high potential for groundwater is located at the foot of Oman Mountains and Al Dhaid Depression covering an area of about 59.33?km², which is 4.40% of the study area. Further hydrological map and data on hydraulic properties of shallow aquifer, as recorded from observation wells in the regions, have been used to validate the produced GPZ map. The validation result showed sufficient agreement between the produced GPZ map.     

Land evaluation studies in semi-arid central alluvial plains area in district Rohtak,Haryana

The study deals with making land evaluation for sugarcane, wheat and paddy cultivation in the semi-arid central alluvial plains in district Rohtak, Haryana. The special feature of this study is the use of soil survey data obtained from the interpretation of aerial photographs (1∶25,000) with limited field checks for making soil classification. Methodology of land evaluation is based on F.A.O. frame work and an attempt has been made to extricate land qualities from the information contained in the texa of soil Taxonomy identified in the surveyed are. The study successfully demonstrates a systematic, fast and economic way of making land evaluation for sound landuse planning in an area for agriculture development. On the basis of this study, highly suitable (S1), moderately suitable (S2), marginally suitable (S3) and currently not suitable (N1) land mapping units for the cultivation of sugarcane, wheat and paddy have been identified and their respective percentage area calculated for the study area.     

Groundwater investigation in semi-arid developing countries, using simple GIS tools to facilitate interdisciplinary decision making under poorly mapped conditions: The Boteti area of the Kalahari region in Botswana

Locating additional long-term groundwater resources in semi-arid regions of developing countries with growing populations is an expensive undertaking. Simple geographic information system (GIS) techniques can be utilised to facilitate efficient application of expensive geophysical techniques and test-drilling by functioning as an interdisciplinary integration and decision-making tool, especially in data-poor and poorly mapped environments where more sophisticated GIS techniques are not applicable. The paper demonstrates this in the context of the search for groundwater alternatives to the dwindling river water supply in the Boteti area of the Kalahari region in Botswana.     

Error model of curves in GIS and digitization experiment

IntroductionCurves are the fundamental geometric elementsin GIS. The uncertainty of their positions has ani mportant influence on those outputs from GISandis the reliable basis for reasonably evaluatingthose outputs .In contrast to measurement error theor…     

Error model of curves in GIS and digitization experiment

A stochastic error process of curves is proposed as the error model to describe the errors of curves in GIS. In terms of the stochastic process, four characteristics concerning the local error of curves, namely, mean error function, standard error function, absolute error function, and the correlation function of errors, are put forward. The total error of a curve is expressed by a mean square integral of the stochastic error process. The probabilistic meanings and geometric meanings of the characteristics mentioned above are also discussed. A scan digitization experiment is designed to check the efficiency of the model. In the experiment, a piece of contour line is digitized for more than 100 times and lots of sample functions are derived from the experiment. Finally, all the error characteristics are estimated, on the basis of sample functions. The experiment results show that the systematic error in digitized map data is not negligible, and the errors of points on curves are chiefly dependent on the curvature and the concavity of the curves.     

Mobile GIS occupancy audit of Ulana informal settlement in Ekurhuleni municipality,South Africa

ABSTRACT

Relocating people in informal settlements and upgrading the lives of those people require consistent commitment, good strategies, and supporting systems. In South Africa, in order to allocate subsidized housing to beneficiaries of an informal settlement, beneficiary administration needs to determine the number of people who qualify for subsidized houses. Without geo-spatial data-based technical verification, conventional methods of occupancy audits are often cumbersome, are unreliable, and do not promote smart and evidence-based decision making. Accordingly, the aim of this study is to propose and develop an Oracle-based mobile GIS tool to conduct an occupancy audit for Ulana, an informal settlement in Ekurhuleni Municipality in South Africa. Android-based tablets were used to collect the geographic and socio-economic attributes of the informal dwelling units (DU). Spatial analysis (in ArcGIS software and geo-spatial modeling environment) and statistical analysis were conducted to produce the occupancy audit. The results indicated that the use of mobile GIS provides up-to-date, accurate, comprehensive, and real-time data so as to facilitate the development of smart and integrated human settlements. The results of this audit also indicated that only 57% of the households residing in Ulana could potentially benefit from receiving a subsidized house. Accordingly, the occupancy audit enables planners to plan appropriate upgrading and housing development strategies for informal settlement. This study demonstrates that successful planning of housing delivery for post independent integrated neighborhoods is not a mere political rhetoric but is viable when it is based on reasonable geo-spatial techniques and information. The use of mobile GIS therefore needs to be extended to other informal settlement upgrading projects in South Africa as well as other cities in the global south. However, proper professional training is required to ensure the successful usage of smart mobile GIS tools.     

基于GIS的丘陵区耕地景观格局时空演变特征分析

以四川省绵阳市涪城区为例,运用景观格局原理与GIS空间分析方法,分析1996--2009年期间耕地景观时空格局及其演变机理（驱动力）。结果表明：13年间,研究区耕地面积呈急剧减少的趋势,变化率明显高于省内丘陵区平均水平;耕地景观空间格局稳定性逐步降低,格局时空变化的地形分异特征显著;变化趋势受坡度、新增建设用地、人口密度、高程、城镇化水平、GDP、起伏度等负向驱动力与灌溉条件、等级公路水平、土地整理程度等正向驱动力因子共同影响。     

GIS中面的游程编码表达、实现与应用

游程编码是一种常用的压缩和表达栅格数据的技术,GIS中面状要素的栅格化有时也采用这种方法。本文主要研究面的游程栅格化方法,设计并实现了一种扫描线算法,主要思路为:计算扫描线与面边界的交点并组织为有序断点链表形式,然后根据扫描行上断点序号的奇偶性建立有序游程链表。为降低栅格化过程中位置精度的损失,提出用实数值记录游程边界的方法。论文还探讨了游程编码的常见操作及其实现,通过实例说明其在GIS面操作中的应用与优势。     

A general framework for error analysis in measurement-based GIS Part 4: Error analysis in length and area measurements

This is the final of a series of four papers on the development of a general framework for error analysis in measurement-based geographic information systems (MBGIS). In this paper, we discuss the error analysis problems in length and area measurements under measurement error (ME) of the defining points. In line with the basic ME model constructed in Part 1 of this series, we formulate the ME models for length and area measurements. For length measurement and perimeter measurement, the approximate laws of error propagation are derived. For area measurement, the exact laws of error propagation are obtained under various conditions. An important result is that area measurement is distributed as a linear combination of independent non-central chi-square variables when the joint ME vectors of vertices coordinates are normal. In addition, we also give a necessary and sufficient condition under which the area measurement estimator is unbiased. As a comparison, the approximate law of error propagation in area measurement is also considered and its approximation is substantiated by numerical experiments.This project was supported by the earmarked grant CUHK 4362/00H of the Hong Kong Research grant Council.     

Using InfoVal method and GIS techniques for the spatial modelling of landslide susceptibility in the upper catchment of river Meenachil in Kerala

A GIS-based statistical methodology for landslide susceptibility zonation is described and its application to a study area in the Western Ghats of Kerala (India) is presented. The study area was approximately 218.44 km² and 129 landslides were identified in this area. The environmental attributes used for the landslide susceptibility analysis include geomorphology, slope, aspect, slope length, plan curvature, profile curvature, elevation, drainage density, distance from drainages, lineament density, distance from lineaments and land use. The quantitative relationship between landslides and factors affecting landslides are established by the data driven-Information Value (InfoVal) — method. By applying and integrating the InfoVal weights using ArcGIS software, a continuous scale of numerical indices (susceptibility index) is obtained with which the study area is divided into five classes of landslide susceptibility. In order to validate the results of the susceptibility analysis, a success rate curve was prepared. The map obtained shows that a great majority of the landslides (74.42%) identified in the field were located in susceptible and highly susceptible zones (27.29%). The area ratio calculated by the area under curve (AUC) method shows a prediction accuracy of 80.45%. The area having a high scale of susceptibility lies on side slope plateaus and denudational hills with high slopes where drainage density is relatively low and terrain modification is relatively intense.     

Integration of remote sensing and GIS in monitoring the dynamics of land cover in Oroba-Kibos catchment area, Kenya

Land cover in Kenya is in a state of fl ux at different spatial and temporal scales. This compromises environmental integrity and socioeconomic stability of the population hence increasing their vulnerability to the externalities of environmental change. The Oroba-Kibos catchment area in western Kenya is one locality where rapid land use changes have taken place over the last 30 years. The shrubs, swamps, natural forests and other critical ecosystems have been converted on the altar of agriculture, human settlement, fuel wood and timber. This paper presents the results of a study that aimed at providing spatially-explicit information for effective remedial response through (a) Mapping the land cover; (b) Identifying the spatial distribution of land cover changes; (c) Determining the nature, rates and magnitude of the land cover changes, and; (d) Establishing the drivers of land use leading to land cover changes in Oroba-Kibos catchment area. Bi-temporal Landsat TM imagery, fi eld observation, household survey and ancillary data were obtained. Per-fi eld classifi cation of the Landsat TM imagery was performed in a GIS and the resultant land cover maps assessed using the fi eld observation data. Post-classifi cation comparison of the maps was then done to detect changes in land cover that had occurred between 1994 and 2008. SPSS was used to analyze the household survey data and attribute the detected land cover changes to their causes. The fi ndings showed that 9 broad classes characterize the catchment area including the natural forests, swamps, natural water bodies, woodlands, shrublands, built-up lands, grasslands, bare lands and croplands. Croplands are dominant and accounted for about 65% (57122 ha) of the total land in 1994, which increased at the rate of 0.89% to 73% (64772 ha) in 2008, while natural water bodies has the least spatial coverage accounting for about 0.6% (561 ha) of the total land in 1994, which diminished at the rate of 3.57% to 0.3% (260 ha) in 2008. Climate, altitude, access and rights to land, demographic changes, poverty, political governance, market availability and economic returns are the interacting mix of proximate and underlying factors that drive the land cover changes in Oroba-Kibos catchment area.     

GIS发展瓶颈、理论及万象GIS实践

阐述了GIS发展中的 3个瓶颈问题:输入、更新、全面的空间概念,并分析了产生这些瓶颈的理论背景,提出了GIS对象结构、系统空间数学基础及结构,矢量、栅格结合的 3个重要理论问题,最后介绍了万象GIS的实践。     

A comparison of the tesseroid,prism and point-mass approaches for mass reductions in gravity field modelling

The calculation of topographic (and iso- static) reductions is one of the most time-consuming operations in gravity field modelling. For this calculation, the topographic surface of the Earth is often divided with respect to geographical or map-grid lines, and the topographic heights are averaged over the respective grid elements. The bodies bounded by surfaces of constant (ellipsoidal) heights and geographical grid lines are denoted as tesseroids. Usually these ellipsoidal (or spherical) tesseroids are replaced by “equivalent” vertical rectangular prisms of the same mass. This approximation is motivated by the fact that the volume integrals for the calculation of the potential and its derivatives can be exactly solved for rectangular prisms, but not for the tesseroids. In this paper, an approximate solution of the spherical tesseroid integrals is provided based on series expansions including third-order terms. By choosing the geometrical centre of the tesseroid as the Taylor expansion point, the number of non-vanishing series terms can be greatly reduced. The zero-order term is equivalent to the point-mass formula. Test computations show the high numerical efficiency of the tesseroid method versus the prism approach, both regarding computation time and accuracy. Since the approximation errors due to the truncation of the Taylor series decrease very quickly with increasing distance of the tesseroid from the computation point, only the elements in the direct vicinity of the computation point have to be separately evaluated, e.g. by the prism formulas. The results are also compared with the point-mass formula. Further potential refinements of the tesseroid approach, such as considering ellipsoidal tesseroids, are indicated.     

Mapping waterholes and testing for aridity using a remote sensing water index in a southern African semi-arid wildlife area

Abstract

Waterholes are a key resource that influences wildlife distribution in semi-arid ecosystems. Mapping waterholes can guide intervening decisions for supplementing water resources and managing wildlife distribution patterns. Although remote sensing provides a key to mapping distribution of waterholes, efficiency of existing remotely sensed methods for detecting waterholes have to be evaluated and even new ones developed. In this study, we evaluated performance of the Modified Normalized Difference Water Index (MNDWI) and Superfine Water Index (SWI) at selected optimum thresholds. Kappa results indicated that MNDWI detects waterholes better than SWI. We further validated MNDWI detected waterholes by testing response of waterhole area to temporal rainfall variability and waterhole persistence to spatial rainfall variability. Extent of MNDWI-detected waterholes varied in relation to temporal rainfall variability (p < 0.05). Waterhole persistence was not associated with spatial rainfall variability which could be explained by differences in waterhole types or low spatial rainfall variability.     

大区域物流配送中车辆路径选择的GIS研究

区域物流配送中车辆线路选择问题(VRP),就是最短路径的选择问题。在大区域的物流配送过程中,影响车辆最短路径选择的主要是公路网络中的交通流量和公路网络的可行路径。本文讨论了基于交通流量变化的VRP的分配模型。研究了交通流量、车速和公路技术等级之间的关系。提出用路段的技术等级作为最短路径选择的路阻权重。试验表明基于公路技术等级路段权重信息的最优路径搜索与单纯从道路长度考虑的最短路径分析相比,显然更实用也更具有实际意义。     

Residential area evaluation using GIS technique: A case study — Part of Bhubaneswar city

To evaluate a planning area or to implement plan procedures, planners need database in the form of land use, population density, housing density and point information regarding various facilities. At present planning tasks are carried out by manual methods where analytical capabilities are limited. Therefore, there is a need for reliable data as well as comprehensive database information indicating physical factors and good analytical tools. In a development plan various standards are specified in zoning regulations for the development of a city. To get an overall view, how these standards are implemented on the ground in planning period, a GIS application can be useful in analysing various amenity standards with respect to population and distances. In this study, for part of Bhubaneswar, basic data was generated from 1988 aerial photographs and other related information was gathered through field survey and secondary sources. The derived information in the form of a map has been entered into computer through digitization. Vector information was later converted into a raster form for the analysis. As per the planning standards catchment areas were created for limited facilities/services like schools, parks, play ground and accessibility to bus stop from main road. The population actually served by these facilities were calculated and compared with the existing planning standards. This particular study demonstrates the use of GIS in one of the planning tasks especially analyzing the residential areas as per the set standards such that improvement schemes can be proposed accordingly in the deficient areas.