3D City and Urban Modeling

The increased availability of high-resolution satellite images and aerial photography in support of detailed terrain surface elevation models assists urban planners and municipal managers to create a model and visualize the urban space in three dimensions. 3D visualization models have a variety of applications in geography and urban studies. Accurate cartographic feature extraction, map updating, digital city models and 3D city models in urban areas are essential for many applications, such as military operations, disaster management, mapping of buildings and their heights, simulation of new buildings, updating and keeping cadastral databases current, change detection and virtual reality. While they are generally used to simply visualize the built environment, there are early signs of them being used as 3D interfaces to more sophisticated simulation models.

Image Credits: University of Texas at Dallas

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In most of these cases the models of buildings, urban features, terrain surface, and vegetation are the primary features of interest. LiDAR data (Light Detection And Ranging) is a mature technology for obtaining the Digital Surface Models (DSMs) of the earth's surface. It is a fast method for sampling the earth's surface with a high density and high positional accuracy. This data when combined with satellite and aerial imagery can be used to create highly detailed Digital Surface Models (DSMs) and eventually Digital City Models.

15cm LiDAR Digital Elevation Model (DEM) - Harris County, Texas USA

Airborne LIDAR has become a rather important information source for generating high quality Digital Surface Models. It offers one of the most accurate, expedient and cost-effective ways of capturing wide-area elevation information to produce highly detailed DSMs. It contains vast amounts of information like buildings, trees, streets, streams and something as small as power lines. The data is in digital format and is directly processed to produce detailed Digital Elevation Models at vertical accuracies of 15-18 cm (6"-7"). Derived products include contour maps, slope/aspect, TIN, three-dimensional topographic images and more.

Image Credit: University of Texas at Dallas

Just a few years ago, the main input data for the production of digital city models and 3D city models were aerial images, terrestrial images, map data, and data derived from classical surveying. The process of geospatial information extraction from these sources was performed manually using heads-up digitization or digitally using image classification algorithms. With today's high-resolution Satellite sensors available at the <0.5m resolution it becomes more practical and economical to utilize Stereo Satellite Image data to generate <3m DSM's for areas located around the World without any requirements for Aerial Mapping permits, licenses or mapping in restrictive airspace.

LiDAR can generate a three-dimensional dense, geo-referenced points cloud for the reflective terrain surface. The original LiDAR data consists of tremendous points returned from all possible reflective terrain objects, including bare-earth, buildings, bridges, vehicles, trees, and other non-ground features. For many topographic, hydrographic, agricultural, and construction applications, the non-ground (bare-earth) returns must be detected, separated, and removed in order to generate the digital terrain model.

3D models can be used as a user-friendly interface for querying the urban environment as a Geographic Information Systems (GIS), for hyper-linking Web-based information, for visualizing model results, and for accessing functional simulation models.

A general classification of 3D city models, based on their operational purposes, might be organized around four main types:

• 3D CAD (computer aided design) models of cities
• Static 3D GIS (geographic information systems) models of cities
• Navigable 3D GIS models of cities
• 3D urban simulation model

If a 3D terrain modeling and visualization application requires good detail pertaining to the terrain features and terrain slopes for critical project decisions, an accurate digital terrain model (DTM) and a digital surface model (DSM) must be available.

Satellite Imaging Corporation produces clear, captivating simulated views of almost any location from high resolution satellite sensors and aircraft imaging data.

For more information on this technology and our services, please contact us.