QUILT: a geographic information system based on quadtrees†

For the performance of geographic information systems, it has been widely recognized that efficient data structures and algorithms supporting proximity based access to spatial data are a crucial ingredient. Because of that, in the last years, a lot of data structures for storage of multidimensional non-point objects have been proposed in the literature (for an overview see our tutorial introduction in this volume). Almost all of these approaches are made to support queries based on spatial neighborhood of objects, so-called proximity queries. Common examples of such proximity queries are range queries, returning all objects intersecting a given (rectangular) region, or nearest neighbor queries, determining the object nearest to a given point. But a geographic or cartographic information system should also support queries that do not exclusively refer to the spatial neighborhood of objects. For example, different versions of spatial data must be organized such that proximity queries to any version of the data can be answered efficiently. Or, given a set of object classes, a spatial query that involves an arbitrary combination of these classes should also be supported. Because of the growing size of data sets to be handled in geographic information systems, an appropriate data organisation to support such and several other application-specific queries becomes more and more important. In this paper, we will present two approaches for access structures supporting the two types of queries mentioned above. Handling of versioned, spatial data is the topic of Section 2, while Section 3 discusses queries on some classes selected from the set of object classes stored in a geographic information system.

This paper is intended to provide better insight into Geographical Information System especially from geospatial technical development perspective. It includes brief introduction into GIS and Remote Sensing. Start from early development GIS as a desktop computing, it has been proved as a power tool in planning and decision making process. It has been able to provide timely accurate and timely information. The strength of GIS in early development is laid on the capability of GIS and Remote Sensing in modelling, analyzing spatial relationships of complex active process, multi criteria decision making and predict spatial object distribution. The overlaying techniques in determining and classifying the underlying process, geographical object has been ever really amazing. In this regard, simultaneously GIS is able to produce information in the form of texts, tabular, chart, thematic and chlorotic map visualization. This capacity is due to a strong component of GIS software which include database management, photogrammetric, geoinformatic engineering, cartographic techniques, word processor and mathematical calculator that are embedded in the GIS Software. Because of these components, GIS is not only able to answer question of what but also to answer question of where. In this regard every geographical object is described by attributes and geometric aspect of the underlying objects. This allows the possibility to detect and to trace the location of static and mobile geographical objects. In early ninety, the strength of GIS has been increased by incorporating 3 D modelling for digital terrain model, landscape, and geomorphology or earth surface and built environment including urban city, road development. In addition to this ninety development, Civil Engineering, Public Health, Mining, Flight Company, City Council, Ministry of Defend, Ministry of transportation, Highway management have been also explored and used. During this period the question of quality information handled and produced by GIS has been big issue. Through intensive research data quality parameters and frameworks, standards, produced by Open GIS Consortium have been also incorporated into GIS. In Malaysia there are several GIS and Remote Sensing have been also development including MACRES and MC GDI.

A nested multi-grid solution algorithm has been developed for an adaptive Cartesian/Quad grid viscous flow solver. Body-fitted adaptive Quad (quadrilateral) grids are generated around solid bodies through ‘surface extrusion’. The Quad grids are then overlapped with an adaptive Cartesian grid. Quadtree data structures are employed to record both the Quad and Cartesian grids. The Cartesian grid is generated through recursive sub-division of a single root, whereas the Quad grids start from multiple roots—a forest of Quadtrees, representing the coarsest possible Quad grids. Cell-cutting is performed at the Cartesian/Quad grid interface to merge the Cartesian and Quad grids into a single unstructured grid with arbitrary cell topologies (i.e., arbitrary polygons). Because of the hierarchical nature of the data structure, many levels of coarse grids have already been built in. The coarsening of the unstructured grid is based on the Quadtree data structure through reverse tree traversal. Issues arising from grid coarsening are discussed and solutions are developed. The flow solver is based on a cell-centered finite volume discretization, Roe's flux splitting, a least-squares linear reconstruction, and a differentiable limiter developed by Venkatakrishnan in a modified form. A local time stepping scheme is used to handle very small cut cells produced in cell-cutting. Several cycling strategies, such as the saw-tooth, W- and V-cycles, have been studies. The V-cycle has been found to be the most efficient. In general, the multi-grid solution algorithm has been shown to greatly speed up convergence to steady state—by one to two orders. Copyright © 2000 John Wiley & Sons, Ltd.

Part 1 What is a geographic information system?: geographical information systems - an overview, Duane F.Marble geographical information systems - a new frontier, Roger F.Tomlinson a classification of software components commonly used in geographical information systems, Jack Dangermond GIS versus CAD versus DBMS - what are the differences?, David J. Cowen. Part 2 Examples of practical applications: MAGI - a state-level grid cell system, State of Maryland ARC/INFO - a modern GIS, Environmental Systems Research Institute technical description of the DIME system, US Bureau of the Census prinicpal components of the census bureau's TIGER file, Joel Sobel the Tiger system - automating the geographical structure of the United States, Robert W.Marx current and potential uses of geographical information systems - the north American experience, Roger F.Tomlinson an experiment in land-use allocation with a geographical information system, C.Dana Tomlin and Kevin M.Johnston Integration Of Geological Datasets For Gold Exploration In Nova Scotia, G.F.Bonham-Carter, F.P.Agterberg and D.F.Wright modeling community vulnerability to hazardous materials using geographical information systems, Robert B.McMaster representing and applying knowledge about spatial processes in environmental management, J.R.Davis, P.Whingham, and I.W.Grant. Part 3 Operations and problems of building a database: creating large digital files from mapped data, Hugh W.Calkins manual digitizing systems, E.Alan Cameron interaction between the cartographic document and the digitizing process, Donna J.Peuquet and A.Raymond Boyle a review of digital data commonly available and some of the practical problems of entering them into a GIS, Jack Dangermond efficient digitizing through the combination of appropriate hardware and software for error detection and editing, Nicholas R.Chrisman. Part 4 GIS internals - data representation and analysis techniques: spatial data models - a conceptual framework and comprehensive review, Donna J.Peuquet historical data as an explicit component of land information systems, Ric Vrana it makes me so CROSS, David Douglas the accuracy of map overlays - a reassessment, Nicholas R.Chrisman. Part 5 Design and evaluation of GIS: establishing a geographical information system in relation to its use, a process of strategic choices, W.H.Erik DeMan a conceptual model of the manual digitizing process, Duane F.Marble, Jean P.Lauzon and Matthew McGranaghan performance eval and work-load estimation for GIS, Michael Goodchild and Brian R.Rizzo liability for information, Earl F.Epstein and Howard Roitman.

In many geographic objects such as a travel planning, the use of web information is significantly increasing. For an efficient support of such work, it is very important to combine web information with map semantics. Current web systems usually do not support map semantics. Conversely, conventional Geographic Information Systems (GIS) do not utilize the web resources. The purpose of the research is as follows: (1) to get semantics from the web contents to realize advanced GIS functions on geographic web searches, and (2) to develop a user interface which can utilize web contents and map semantics in an effective integrating way. For such a purpose, we construct two map semantics about geographic characteristics and relationships available on the web. Utilizing semantics, we have developed a prototype system, KyotoSEARCH; its main function is to support users’ information navigations among the web, the map and web-based geographic knowledge, in an integrated way.

Data mining for spatial data has become increasingly important as more and more organizations are exposed to spatial data from sources such as remote sensing, geographical information systems, astronomy, computer cartography, environmental assessment and planning, etc. Recently, density based clustering methods, such as DENCLUE, DBSCAN, OPTICS, have been published and recognized as powerful clustering methods for data mining. These approaches have run time complexity of O(nlogn) when using spatial index techniques, R + tree and grid cell. However, these methods are known to lack scalability with respect to dimensionality. In this paper, a unique approach to efficient neighborhood search and a new efficient density based clustering algorithm using EIN-rings are developed. Our approach exploits compressed vertical data structures, Peano Trees (P-trees), and fast P-tree logical operations to accelerate the calculation of the density function within EIN-rings. This approach stands in contrast to the ubiquitous approach of vertically scanning horizontal data structures (records). The average run time complexity of our algorithm for spatial data in d-dimension is \(O(dn\sqrt{n})\). Our proposed method has comparable cardinality scalability with other density methods for small and medium size of data, but superior speed and dimensional scalability.

Geographic information systems (GISs) are widely used for representation, management, and analysis of spatial data in many disciplines. In particular, geoscientists increasingly use these tools for data integration and management purposes in many environmental applications, ranging from water resources management to the study of global warming. Beyond these capabilities, geoscientists need to model and simulate three-dimensional (3D) dynamic fields and readily integrate those results with other relevant spatial information in order to have a better understanding of the environmental problems. However, GISs are very limited for the modeling and simulation of spatial fields, which are mostly 3D and dynamic. These limitations are mainly related to the existing GIS spatial data structures that are static and limited to 2D space. In order to overcome these limitations, we develop and implement a new kinetic 3D spatial data structure based on Delaunay tetrahedralization and a 3D Voronoi diagram to support a 3D dynamic field simulation within GISs. In this article, we describe in detail the different steps from discretization of a 3D continuous field to its numerical integration, based on an event-driven method. For validation of the proposed spatial data structure itself and its potential for the simulation of a dynamic field, two case studies are presented in the article. According to our observations, during the simulation process, the data structure is maintained and the 3D spatial information is managed adequately. Furthermore, the results obtained from both experiments are very satisfactory and are comparable with the results obtained from other existing methods for the simulation of the same dynamic field. To conclude, we discuss the current challenges related to the development of the 3D kinetic data structure itself and its adaptation to 3D dynamic field simulation and suggest some solutions for its improvement.

A bi-level object-oriented data model together with a user query language called OFQL is designed which can support applications like GIS (geographic information systems). The data model is divided into two layers, the higher-level data model and the lower-level data model. The higher-level data model or the geographic object data model primarily consists of the geographic objects and a set of semantic spatial functions through which the topological relationships of the geographic objects are defined or derived. The lower-level data model or the geometric object data model has geometric objects which are the actual spatial representations of the geographic objects in the higher-level data model. It also has a set of geometric functions that retrieve, manipulate, and compute for geometric objects. The general architecture of a GIS system using this data modeling approach consists of two modules: the query processor and the function implementor. With the OFQL user-interface, the user is able to pose queries of a geographic nature without knowing the details of the spatial representation and computation of the geographic objects.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

This paper proposes a novel vision-aided navigation architecture to aid the inertial navigation system (INS) for accurate unmanned aerial vehicle (UAV) localization. Unlike previous image localization methods such as scene matching and terrain contour matching, our approach registers meaningful object-level features extracted from real-time aerial imagery with the data of geographic information system (GIS). Firstly, we extract from aerial images the widely distributed object features including roads, rivers, road intersections, villages, bridges et al.. Then, the extracted image features are delineated as geometrical points and vectors, which coincide with the representation of GIS data. Finally, GIS model is constructed by corresponding geographical object information from GIS data, and visual geometrical features are registered with GIS model to obtain the absolute position of the image. The proposed method adopts GIS as reference data, thus the storage requirement is lower than that of scene matching. In addition, all steps of this approach can be calculated efficiently, while the computational cost of terrain contour matching is very high. Simulation results demonstrate the feasibility of the proposed method for UAV localization.

ABSTRACTThe tight coupling between geospatial data and spatial analysis results in high costs in terms of efficiency when developing algorithms to accommodate different types of data, even when the analysis tasks are the same. Universal GIS (Geographic information system) algorithms, as alternatives to tightly coupled approaches, can reduce development costs. However, a unified representation of spatial data is necessary to support the development of universal GIS algorithms. To this end, this research proposes and implements a template-based approach using geometric algebra to create a unified representation of multidimensional data. The template is composed of parameters and operators for GIS representation and computation. The template approach can support general GIS analyses with parameter unfolding and operator integration methods. A case study of intersection analysis shows that developing programming scripts based on computation templates is much simpler than traditional methods. The results suggest that the template-based method is more efficient than traditional methods and more convenient for high-dimensional applications.

While the use of three-dimensional (3D) geographical information system (GIS) is becoming in rapid development and being used in various fields such as urban and regional planning, disaster management and planning, mobile navigation and etc., commercial and open source GIS software packages tend to offer 3D-GIS functionalities for their products. On the basis, GIS analysis functions are to provide information with respect to geographical location and by having 3D spatial data as an input, it will give advantages in providing horizontal position information. However, to analyze moving objects (temporal) in 3D seems not an easy task and not fully supported by current GIS platform packages. Previously in two-dimensional (2D) GIS practice, main issue addressed by researchers in managing temporal spatial objects is GIS packages were designed based on hardware and software constraints whereby it should be based on the temporal spatial objects ontology. Nowadays, the trend of managing temporal 3D data is via 3D spatial simulation or animation. This approach will not in assistance for GIS users in conducting spatial queries. Without having a suitable ontology and valid topological data structure for temporal 3D data, it will cause repetitive of temporal data (redundancy) and complications in executing spatial analysis in 3D environment. Therefore this paper focuses on the ontology for managing moving 3D spatial objects (i.e. air pollution, flood). The characteristics of moving objects were reviewed thoroughly by categorizing it based on its different appearances. Moreover, existing methods in managing temporal database were addressed and discussed for its practicalities. Another important aspect in managing temporal 3D objects is the implementation of topological data structures for 3D spatial objects were reviewed. In the last section of this paper it summarized the issues and further ideas towards implementing and managing temporal 3D spatial objects in GIS based on the Geoinformation Ontology (GeO).

A linear quadtree compression scheme for image encryption

Geographic information systems (GIS) are becoming more usual due to the improved performance of computer systems. GIS applications are being developed using the three-tier software architecture traditionally used for general-purpose information systems. Even though this architecture is suitable for GIS applications, the special nature and exclusive characteristics of geographic information pose special functional requirements on the architecture in terms of conceptual and logical models, data structures, access methods, analysis techniques, or visualization procedures. In this paper, we propose a generic architecture for GIS that provides support for the special nature of geographic information and conforms with the specifications proposed by the ISO/TC 211 and the OGC. Our strategy to achieve this goal consists of two steps: (i) we analyze the special characteristics of GIS with respect to traditional information systems, (ii) and we adapt the traditional three-tier architecture for information systems to take into account the special characteristics of GIS. Finally, we have tried to apply the architecture that we propose in the development of a complete and complex real-life GIS application using commercial tools in the analysis, design and implementation. We describe this application, and we use it to describe the limitations of current commercial GIS development tools by analyzing the differences in the architecture of the resulting system with respect to our proposal.

Quadtrees represent two-dimensional (spatial) data in a way which takes advantage of spatial coherence in the phenomenon being represented. One major advantage of quadtrees is that they they are very effective for overlay (Boolean) operations; perhaps more important is the fact that quadtrees are compatible with digital elevation models in grid form. This paper reviews the use of quadtrees in geographical information systems. Attention is focused on linear quadtrees and, in particular, on two-dimensional run-encoding, an effective storage structure for quadtrees.

In this thesis, concepts for developing Spatial Data Infrastructures with an emphasis on visualizing 3D landscape and city models in distributed environments are discussed. Spatial Data Infrastructures are important for public authorities in order to perform tasks on a daily basis, and serve as research topic in geo-informatics. Joint initiatives at national and international level exist for harmonizing procedures and technologies. Interoperability is an important aspect in this context - as enabling technology for sharing, distributing, and connecting geospatial data and services. The Open Geospatial Consortium is the main driver for developing international standards in this sector and includes government agencies, universities and private companies in a consensus process. &#13;\n3D city models are becoming increasingly popular not only in desktop Virtual Reality applications but also for being used in professional purposes by public authorities. Spatial Data Infrastructures focus so far on the storage and exchange of 3D building and elevation data. For efficient streaming and visualization of spatial 3D data in distributed network environments such as the internet, concepts from the area of real time 3D Computer Graphics must be applied and combined with Geographic Information Systems (GIS). For example, scene graph data structures are commonly used for creating complex and dynamic 3D environments for computer games and Virtual Reality applications, but have not been introduced in GIS so far. &#13;\nIn this thesis, several aspects of how to create interoperable and service-based environments for 3D spatial data are addressed. These aspects are covered by publications in journals and conference proceedings. The introductory chapter provides a logic succession from geometrical operations for processing raw data, to data integration patterns, to system designs of single components, to service interface descriptions and workflows, and finally to an architecture of a complete distributed service network.&#13;\nDigital Elevation Models are very important in 3D geo-visualization systems. Data structures, methods and processes are described for making them available in service based infrastructures. A specific mesh reduction method is used for generating lower levels of detail from very large point data sets. An integration technique is presented that allows the combination with 2D GIS data such as roads and land use areas. This approach allows using another optimization technique that greatly improves the usability for immersive 3D applications such as pedestrian navigation: flattening road and water surfaces. It is a geometric operation, which uses data structures and algorithms found in numerical simulation software implementing Finite Element Methods. &#13;\n3D Routing is presented as a typical application scenario for detailed 3D city models. Specific problems such as bridges, overpasses and multilevel networks are addressed and possible solutions described. The integration of routing capabilities in service infrastructures can be accomplished with standards of the Open Geospatial Consortium. An additional service is described for creating 3D networks and for generating 3D routes on the fly. Visualization of indoor routes requires different representation techniques.&#13;\nAs server interface for providing access to all 3D data, the Web 3D Service has been used and further developed. Integrating and handling scene graph data is described in order to create rich virtual environments. Coordinate transformations of scene graphs are described in detail, which is an important aspect for ensuring interoperability between systems using different spatial reference systems. The Web 3D Service plays a central part in nearly all experiments that have been carried out. It does not only provide the means for interactive web-visualizations, but also for performing further analyses, accessing detailed feature information, and for automatic content discovery.&#13;\nOpenStreetMap and other worldwide available datasets are used for developing a complete architecture demonstrating the scalability of 3D Spatial Data Infrastructures. Its suitability for creating 3D city models is analyzed, according to requirements set by international standards. A full virtual globe system has been developed based on OpenStreetMap including data processing, database storage, web streaming and a visualization client.&#13;\nResults are discussed and compared to similar approaches within geo-informatics research, clarifying in which application scenarios and under which requirements the approaches in this thesis can be applied.&#13;\n