Student Name: Chung Hiu LamStudent ID: 09165566dQ11. It has been argued that off-the-shelf 3D GIS software cannot model the complex3D cityscape in Hong Kong.Critically evaluate the validity of this argument.IntroductionThree dimensional modeling popularity has beenraising in Geographical InformationSystem (GIS) for data analysis and visualization.As A.Scianna(2010) pointed out, theneed for three dimensional feature has been remarkably increased during past few yearsin GIS. Usually three dimensions helps to understand data immediately by betteranalysis of a situation or a model.1 With advancing technology, many off-the shelf 3DGIS software become able to create complex 3D model. However, Hong Kong is a highdensity city with complex cityscape, which may be difficult for software to model. Inthis article, I will evaluate the validity of the argument“off-the-shelf 3D GIS softwarecannot model the complex 3D cityscape in Hong Kong”. I will focus the term “model”to physical modeling.Cityscape of Hong KongAccording to Oxford dictionaries, cityscape is defined as the visual appearance of a cityor urban area, or similar term as city landscape.2 Other dictionary sources such asfree-dictionary also suggest cityscape as a view of a city, or a section of a city regardedas a scene.3As a renowned financial center, Hong Kong has complex cityscape withmany irregularhigh-rise buildings. According to Hong Kong Planning department,Hong Kong is a crowded city with high densities of development, intensive land uses,low level of vegetation coverage and highly altered topography. Oldest urban area islocated on the north coast of Hong Kong Island and the Kowloon Peninsula, wherebuildings are in mixed ages, with some historical buildings and little vegetation lyingbetween, forming dense and irregular urban form.The reclamation side of Hong KongIsland and Kowloon lies commercial buildings which are tall and have special shape,forming a mixed city-grid urban landscape. Extensive residential area with some1 A. Scianna & A. Ammoscato, 3D GIS data model using open source software. ISPRS Archive Vol.XXXVIII, Part 4-8-2-W9, “Core Spatial Databases-Upding, Maintenance and Services-from Theory toPractice” ,p.120, Haifa, Israel, 20102 Oxford dictionaries, definition of cityscape: http://oxforddictionaries.com/definition/cityscape3 Free-dictionary, definition of cityscape: http://www.thefreedictionary.com/cityscape
medium and high-rise buildings canbe found at the edge of the urban area.4Introduction to 3D modelingAs Dan Ryan (2011) mentioned, 3D modeling is the procedure of developing amathematical, wireframe model that represents a 3D object using specialized software.A 3D model is created using a set of points in three axes, X, Y and Z, with linkage ofgeometric data such as lines and curved surfaces. 5 3Dmodel can be tangible orintangible, depending on the representation method.Most of the3D model creating software uses four methods. They are polygonalmodeling, primitive modeling, NURBS modeling and patch modeling.Polygonal modeling uses a group of vertices and edges, together with advancedmathematic algorithm, to generate 3D surface by putting a “skin” over the mesh.6 Therendering of model is fast but may be difficult to create accurate curved surface.In constructing 3D model, primitive modeling uses default 3D objects such as cubesand balls.7 By combining these objects, a more complex 3D model can be produced.This method is the easiest and simplest as the model is already well defined.Non-uniform rational B-spline (Nurbs) modeling is similar to polygonal modeling, butsince it joins different spline in space, it is curved based and curved surface is moresmooth and accurate. Patch modeling creates 3D model by stitching square together toform a pattern. Most off-the-shelf 3D modeling software are using polygonal andNURBS modeling method to create 3D model.3D modeling is useful to visualize data, especially concept and idea that is difficult torepresent using 2D model. Through 3D visualization, the model can be viewed in manyways which represent a problem better. Higher accuracy of the model improves theability of using it for analysis and case study. 3D model also provides a lifelikeexperience for users, where it is much more interesting and effective for users to view.3D model procedures4 HK landscape, by planning department:http://www.pland.gov.hk/pland_en/p_study/prog_s/landscape/e_executive_summary_hp/es_index.htm5 Dan Ryan, History of computer graphics: DIr Associates Series, Author House, p.37, 20116 Mario Russo,Polygonal modeling: basic and advanced techniques, Wordware Publishing, p.3, 20067 Shamms Mortier,The Bryce 5 Handbook, Charles River Media, p.38, 2002
To model a cityscape, 3D modeling is not the only process. There are many procedureswhich affects the details and accuracy of the model. The first step is data acquisition,which collects qualitative 3D GIS data for reconstruction. The second step is to usemodeling software to build model in 3D,follow by visualization and analysis of themodel. At last the cityscape is presented using different devices.Data acquisitionIn data acquisition, we focus on collecting qualitative 3D GIS data such that theaccuracy of the model can be improved.Technique such as laser scanning, radar,thermal and seismic, is frequently used for data acquisition. One of the recent methodsthat can produce high quality 3D GIS data is Light Detection and Ranging (LIDAR).According to Wehr and Lohr (1999), “LIDAR is an active remote sensing techniquethat determines the distance between the sensor and the target by accurately measuringthe round-trip time of a pulse of laser energy.”8The application follows laser scanningtechnique which creates point clouds of the earth ground. As the light can penetratewoodland and survey the ground surface accurately, while surface such as concretebuilding will be reflected, LIDAR is useful to form a high resolution digital elevationmap and collect building attributes for modeling 3D cityscape.Other methods such asradar performs a similar process but with different accuracy of 3D GIS data. The mainconstraint for these types of data acquisition is that the interior part of the buildingcannot be accessed, which means the attribute of inner building is not collected. It is notpossible for modeler to use such data to build 3D cityscape which involves interior partof the building.Modeling using 3D GIS software3D GIS modeling software is essential to build 3D model. 3D GIS software is softwareused to create, manage, analyze and display geospatial data on digital maps in 3D. Itshould be able to view, explore, create and edit data, store and transform data intodifferent coordinates systems, analyze data using query on dataset, as a result, create 3Dmodel that is geometrically correct with newly obtained information from analysis.Much Off-the-shelf 3D GIS software is available in both commercial and open source.Some leading 3D GIS software includes Autodesksuite, ESRI ArcGIS, etc. Thefollowing paragraphs introduce different types of 3D GIS software which usermay beable to create complex 3D cityscape.8 Wehr A, Lohr U, Airborne laser scanning – an introduction and overview. ISPRS J Photogramm,p.68-82, 1999
AutoCAD and Autodesk 3d Max is software enabling user to design and draft 3Dmodel. Developed by Autodesk, Inc, it provides primitive model such as box andfor beginners, and produces advanced 3D objects using polygonal modeling technique.Autodesk continues to improve 3D modeling functions, where editing of 3D modelbecome easier.Quality rendering is possible with mental ray engine, and objects candisplayed faster and better.9ArcGIS is an integrated collection of GIS software. Through the geospatial analysis,data reconstruction and edition, 3D model can be easily produced. For example,input GIS data into digital map, then select attribute height and extrude, and a simple3D model within the map area is constructed. A more complex and detailed model canbe built using plug-in such as Google sketch up. In the latest version of the ArcGIS,functionally of 3D analyst is improved with better face format compatibility and aaccurate 3D object shapes.10GeoMedia 3D is a 3D GIS software which is focused on geospatial processing forgovernment, transportation and utilities, etc. User can model and visualize 3D data inGeoMedia. A more advanced function includes integration of surfaces, imagery,data and vector data to create 3D model of all data sources.113D GIS software which shares little market shares can be powerful too. SpacEyesbuilder is software which can represent cartographic data in 3D. It supports input suchas DTM, geo-referenced images and GIS data. Using tools of visualization anda detailed 3D model is created.12With many types of GIS format, most software is able to support different standardformat of data such as shape and jpeg.Visualization of 3D modelAfter 3D modeling, the next step is to visualize the model. Visualization is anway to communicate abstract and concrete ideas using visual perceptive such asdiagrams, animations and images. 13Usually 3D modeling software has its own 3Dviewer to visualize and analyze the model. For example, Autodesk 3dmaxhas an9 Autodesk official website: http://usa.autodesk.com/3ds-max/10 ArcGIS official website: http://www.esri.com/software/arcgis/11 GeoMedia 3D official website: http://www.intergraph.com/sgi/products/geomedia3d.aspx12 SpacEyes official website: http://www.spaceyes.com/index.php?option=com_frontpage&Itemid=9913 Chaowei Yang,David W. S. Wong,Qianjun Miao, Advanced Geoinformation Science, CRC Press,p.240
inbuilt function to render 3D model and make it as animation or video. SpacEyes hasindependent 3D viewer to visualize the 3D model. It is rather a simple task to converta 3D model to a view.3D model presentationThe last process is the presentation of 3D model.Previous section mentioned thatsome software is able to render a video to visualize the model. In reality, most of thecompany present 3D model through computer and projector, which project the modelto screen in 2D. Some advanced hardware such as 3D projector can project model in3D. Another method which provides an interactive presentation is 3D printing. 3Dprinting is an additive manufacturing technology where 3D object is created byprinting glue onto a powder bed, and forms a 3D structure by successively stickingthepowder.14 It allows user to touch the 3D model and explore it in detail, whichprovides better experience in viewing the model in reality.Example of 3D cityscape modelingIt is possible to integrate different methods discussed before to model a complexcityscape.Seattle, a busy city which is located in United States, had conducted projectto visualize the entire cityscape using 3D GIS software. To start modeling, accuratedata is needed. This was collected and processed to AutoCAD and Autodesk 3d maxdesigning software. Then professionals create buildings, landscape, streetscape andinfrastructure with details in 3D. Afterfine-tuningand 3D rendering, the whole virtualcityscape is produced and presented on the screen. The 3D model is photorealistic andis able to help developer analyze problem and make better decision.15From the previous example, it illustrates the possibility to model complex 3Dcityscape ina crowded city.Although Hong Kong cityscape may be more complicatedthan Seattle, where many building heights are unknown and shapes are irregular.It ispossible to use LIDAR to solve the data deficiency and improve data quality, whilemodeling software is able to model complex 3D object. For example, bank of Chinahas irregular building shape, the 3D model can easily be found in 3D warehouse.It14 Ian Gibson,David W. Rosen,Brent Stucker, Additive Manufacturing Technologies: Rapid Prototypingto Direct Digital Manufacturing, Springer, p.30, 201015 Parsons Brinckerhoff, Seattle Design Visualization, Autodesk Inc:http://usa.autodesk.com/adsk/servlet/item?siteID=123112&id=15834513
draws a conclusion that off-the-shelf 3D GIS software is able to create 3D cityscape,attributes such as building heights, materials,infrastructure and landscape are wellpresented.Arguments for the statementIt follows a question on how detail the buildings are in the 3D model. One of the mostdifficult problems to model Hong Kong cityscape is that there are many mixed-usebuildings.For example ground level is in commercial use while the upper part isresidential area.The floor area and façade is different and is troublesome to model it.Also, one of the most famous scenes in Hong Kong is the streetwith full of neon signand advertisement banner. It is extremely hard to include all signs in the model.Another concern would be the scale of the project. Cityscape can be small or largedepending on the project scale. Large scale project tends to use more time andresource, and not all organization could afford the cost.These constraints may besolved by investing more time and money to collect data and develop the model, andmanage the project within suitable scale. The final problem comes with the perceptiveof 3D model. Most of the methods above visualize exterior part of the cityscape,which means only concern the outer part of the building. However, perceptive ofcityscape from the interior part of building should also be considered to produce alifelike experience using the model. Currently not much 3D GIS software couldmodel interior part of the building easily, or it is rare to see company using interiorpart to represent a cityscape.ConclusionTo conclude, to a small extent I think off-the-shelf 3D GIS software cannot model thecomplex 3D cityscape in Hong Kong. From the article we discuss the most importantsteps in 3D modeling, where accurate data can be collected by using LIDAR.3Dmodeling, visualization and analysis can be done by different 3D modeling software,and be presented using different output devices.The remaining problem lies on howdetail the model should be and what perspective the model should be at. Therefore, aslong as you have accurate GIS data, enough time and money, technically it is possibleto model the complex 3D cityscape in Hong Kong.