Urban planners have traditionally portrayed our world in two dimensions. However, we live in three dimensions, and now this flat earth representation is changing dramatically. X-y maps and plans are climbing z-wards into the third dimension.
Urban modelling and visualisation are coming of age. To be precise, these terms should be 'geo-modelling' and 'geovisualisation'. The 'geo' prefix refers to the data and imagery being in a quantifiable, real world co-ordinate system. As opposed to the purely arbitrary co-ordinate system of, say, the tombs raided by Lara Croft.
Maybe that arbitrary system explains why she invariably gets lost.
Moreover, venturing into the fourth dimension, today's urban models also run in real time. They are interactive: the viewer can fly and zoom wherever they will, no longer restricted to the (increasingly passé) pre-rendered fly-through.
In local government, this new technology is making informed decisions easier for those unfamiliar with interpreting the outputs from CAD and GIS. The previously complex plans and imagery have come alive - both for those who call the shots, the politicians - and those who foot the bills, the ratepayers.
The terms 'modelling' and 'visualisation' seem interchangeable, but, according to Stanley Tan of SIMmersion Holdings, there is a key difference.
'3D modelling in the urban environment has been around for decades. It's known as CAD. Numerous companies produce CAD software, such as Autodesk's AutoCAD and Bentley's MicroStation, which are geared towards producing prerendered 3D environments. 3D visualisation models have to be driven by a real-time 3D engine.'
'The core issue in our industry is the ability to render and visualise big environments in real time,' Tan emphasises.
'That's what gaming technology has done. It's enabled us to visualise highly detailed and really complex 3D models in a real time video environment.'
Underlying the 3D visualisation is the Digital Terrain Model, which is sourced from contour information via vector Triangulated Irregular Networks (TINs), or from raster georeferenced orthorectified aerial photography. This imagery can be draped over the DTM, and GIS layers can be added as required.
The heights of buildings are determined from photogrammetry (using stereo aerial images), from 3D architectural CAD data, or from attributes in the GIS database. 'Aerotriangulation, using ground control points, is performed to make aerial images ready for 3D stereo measurement and feature extraction, using a digital photogrammetry workstation such as CC-VisualStar,' says Kilian Ulm of CyberCity AG. 'Using this approach, we are able to deliver a 3D model with an accuracy of 15-30cm.'
An important distinction should be made between True Orthophotos and Orthophotos. 'In trueorthophotos, the aerial images are rectified not only on the DTM, as in a normal orthophoto, but also on the 3D building models,' says Ulm. 'This means in a true-orthophoto you don't see any facades projected on the ground, or roofs in the wrong positions. This is absolutely necessary in a 3D simulation where you're driving in a 'virtual' car. You don't want to drive over facades!'
A cheaper and more accurate alternative to aerial photography for smaller sites is airborne laser scanning. North Surveys has developed a tracked kinematic scanning technique, which they state is 'revolutionising true 3D point cloud data acquisition'.
North's surveyors convert cross section data into 3D point cloud scan data, allowing it to be used for 3D visualisation and modelling. Their mobile scanner, travelling at 3.6 km/hr, can cover 20 kilometres in a day.
A visually pleasing 3D model needs the 'wire frame' blocks representing the structures to be rendered with photographs of the actual buildings. For large areas, this can be efficiently achieved by using oblique aerial photography, typically at 15 cm resolution. Dozens of images taken from different viewpoints will capture almost all of the faces of the target structures.
A semi-automated process then pastes the oblique photos onto the buildings' facades. Their roofs are textured automatically from the stereo aerial images. The software compares the textures for each building from the various photos available, then chooses the best texture, based on pixel size and viewing angle. Streetscapes can be enhanced by adding 3D models of people and trees, to add realism when zooming in.
Digital photos taken from the street provide more detailed images. However, these higher resolution (sub-centimetre) images require editing to remove, for example, an unsightly garbage truck parked in front of a showcase corporate headquarters. The image can be flatteringly personalised too; a virtual (and no doubt beaming) boss can be placed at the office entrance.
The software behind 3D visualisation is evolving at a startling rate, as is the proficiency of the interfaces between all the software packages in use. The software has to be able to import and export 3D data in the commercial formats used by GIS, CAD, photogrammetry, geodatabases, virtual reality, imagery and animation.
For council planners, who customarily have used software such as AutoCad, MicroStation, ArcGIS, MapInfo, etc, this software maze can be baffling. To get the most from 3D visualisation, they need to understand 3D modelling programs and visualisation packages such as 3D Studio Max, VNS, ArcScene, SiteBuilder 3D, TerrainView-Globe, Skyline, SIMurban, or others. The learning curve is steep for those getting into 3D visualisation, as is the cost. These programs don't come as freeware.
Not surprisingly, councils and developers are turning to consultants specialising in the latest technology. Tony MacDonald, 3D Manager for Arterra Interactive, says: 'Having expertise in just one or two software programs is not going to cut it when there are so many new and varied programs around.
'The goal is to always create a variety of visualisations which will assist the project teams and the general public to understand, evaluate and refine the design during the various phases of development.'
3D visualisation is being increasingly used by councils, planners, property developers and even security agencies. It's revitalising the planning and presentation of complex urban projects, is being used more in Development Applications and is simplifying community consultation and consensus.
It has a range of practical applications. Real time interactive scenes, animations and still views are easily accessed. Shadows can be generated for any time of day, on any day of the year. Line-ofsight analysis is of particular interest to telecommunications and security companies.
Viewshed analysis can resolve potential complaints from those living near proposed buildings. Its interactive nature means that a viewpoint can be taken from any resident's window and show, say, how much of a prized ocean view will be lost. Or you can zoom out and get the big picture of how the development fits in with its surroundings, either from a bird's eye view or from nearby hills.
Concerns about the aesthetics and the environmental impact of a new project can be addressed. Building and landscape designs can be altered on the fly. Different species and densities of trees and shrubs in the landscaping can be trialled virtually.
As the visualisation is geo-referenced, linear measurements can be made. Noise buffering can be gauged. Large projects can be shown as they grow over time.
The time taken to process DAs can be reduced, as more analysis can be done before submission. The City of Perth recently called for expressions of interest to provide a 3D visualisation of its CBD. Up till now, the city has used a physical model, with white blocks to represent buildings.
Robert Munro, Perth's planning and development project officer, explains why his council is planning to use 3D computer visualisation: 'more and more companies, developers and the like, are using fly-throughs,' he says. 'They're more a promotional and advertising medium than an actual development plan. So we were seeing all these things that were visually very impressive, but were often eye candy, in that they weren't conveying a completely accurate picture.
'The primary purpose [of acquiring 3D visualisation] is to get around that issue when looking at development applications. We're concerned about the level of information that we're able to provide, particularly for our elected members, so that they can make informed decisions.'
The council is also considering other benefits. 'You can add value to it by getting it onto the web,' says Munro. 'You can do things like create tourist trails, or provide cut down versions for public access. The more you can get out of it, the more you can justify the cost.'
Much of the emotional arguments around a new development can be diffused using this technology, which could prevent expensive and time wasting litigation. Wild claims can be made by opponents or supporters of a controversial project. A 3D visualisation can accurately portray the proposed structures, allowing more rational outcomes.
Once up and running, 3D visualisation can be integrated into software with which council staff are familiar, such as ArcGIS 3D Analyst. The 3D data can be readily used, along with their existing 2D data, for GIS analysis, urban planning, utility mapping, tourism promotion etc.
Limited 'read only' versions can be created, with particular GIS layers displayed on a 'need to know' basis. For example, the sewerage department staff could use a tailored 3D model to perform slope analysis on a gravity fed sewer system.
3D visualisation offers a potent, cost effective and geospatially accurate tool for urban planners. It provides an easily understood picture of a proposed development to all the interested parties: the councillors, ratepayers, developers and property owners.
And, crucially, it has the power of being interactive. The proposed building is blocking your view? Let's slice off a floor. Move it ten metres to the left. Put those trees over there.
Now, how's that looking?
Derek Tickner ticspics@iinet.net.au is a freelance writer/photographer and GIS Project Officer with Gosford City Council.
