3d objects as analytical tools - gis.pdf

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View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Universiti Teknologi Malaysia Institutional Repository 3D ANALYTICAL TOOLS FOR TERRAIN SPATIAL OBJECTS Alias Abdul Rahman and Chen Tet Khuan Center for Geographic Information and Analysis & Department of Geoinformatics Faculty of Geoinformation Science and Engineering Universiti Teknologi Malaysia 81310 UTM Skudai, Johor Malaysia [email protected] KEY WORDS: GIS, 3D datasets, Buffering Algorithms, Interface ABSTRACT: Geographic information system inevitably moves towards handling and manipulating not just two-dimensional data but more than that e.g., three-dimensional (3D) and four-dimensional (4D) spatial objects. At this moment very few GIS systems offer real 3D analytical operations or analyses with the exception of visualization. Buffering is one of the analytical tools that should be available in any 3D GIS system. This paper discusses 3D buffering aspect in details such as the mathematics, the geometry as well as the development of user interface of the 3D buffering. We tested our buffering approach by using photogrammetrically captured datasets. Finally, the paper provides outlook to the proposed work towards the development of advanced 3D analytical solutions in 3D GIS domain. 1. INTRODUCTION 2. 3D ANALYTICAL TOOLS Geographic information system (GIS) deals with modeling, We have developed 3D analytical tools for terrain spatial manipulation, management, analysis, and representation of objects. The tools are point buffering, line buffering, and geographically referenced data. GIS tools and applications are polygon buffering in 3D space and the results could be not only for GIS specialist, but also for those who could visualized by using commercial software like ArcView. The manipulate spatial data and make use of the generated paper presents each algorithm in detailed and demonstrates information that relates to locations (with attributes data). some visual output from the experiment. Spatial data contains positional values and the attributes describe what the data is and eventually the information of 2.1 Point Buffering objects and their surrounding through spatial analysis operations. We would not be able to understand the objects Point can be defined as single coordinate triplets of x, y, z and fully if the analytical operations were not done in 3D space as can be used to represent point features like boreholes, control we perceived in the real world (Abdul-Rahman et al, 2002) and towers, etc. (Raper, 2000). Point objects or features such as Zlatanova (2000). Current GIS system faces some difficulties survey ground control points, towers along a power line, spot in handling certain types of datasets e.g. 3D dataset as most GIS heights, other features such as ponds, lakes, underground users dealt with in 3D applications for example in objects such as ore bodies, rocks, etc. Typical analytical GIS environmental monitoring, urban mapping, city navigation, operation that could be done on these objects is proximity geological exploration, etc. need a system that able to do some analysis like buffering. This analytical operation could be done 3D analysis or analytical operations. The problem of doing in 3D and would provide better understanding of the such buffering operation in 3D motivates us to do some phenomena. Our buffering algorithm for point features is based experiments in this 3D analytical operation. In order to have a on sphere geometry, i.e. a point of x, y, z coordinates gradually 3D GIS system that handles real-world spatial objects, the evolved into a sphere shape and its size depends on the distance system should not be constrained by single XY plane only. from the centre of a point object. The following figure (Figure Assuming 3D analysis is one of the core components of the 3D 1) shows the basic geometry of the generated surface around a GIS (Zlatanova et al, 2002), an investigation towards 3D point object. buffering as a framework for 3D analytical operations for such system is inevitable. Polar This paper discusses the analytical tools, the buffering algorithms (for points, line, and surface) in section 2.1, section Circle 2.1, and section 2.3 respectively and forms major discussions. Preliminary results of the algorithms are presented at the end of each section. Study area and the interface development are briefly described in section 3 and 4. Finally, the conclusions in section 5. Origin Figure 1: A sphere from a point.  } The technique to generate a sphere begins with the creation of compute the upper and lower polar points; polygon surface as implemented by ESRI, see (ESRI, 1998) that is the implementation of the PolygonZ to create a solid for (i=0;i