Lecture 9: Introduction to 3D Spatial Visualization

Motivation: Industrial Revolution

• 1765 (1st revolution)

  • Mechanization - led by the steam engine

• 1870 (2nd revolution)

  • Mass Production - driven by electricity and oil-based power

• 1969 (3rd revolution)

  • Automated Production - supported by electronics and information technologies

• Today (4th revolution)

  • New technologies - Internet of Things (IoT), Artificial Intelligence (AI); Big Data, Cloud, Cyber-Physical Systems…

Smart Cities and the 4th Industrial Revolution

• Smart City, one of the core technologies of the 4th Industrial Revolution, is a technology to respond to unpredictable changes in the future society

• Digital twin technology, is a key technology for implementing smart city platforms

Digital Twin Cities

• Digital twins aim to represent the physical world to aid in data-driven decision making by mirroring real-world processes

• The digital twin must be composed by an integrated spatial system in order to perform these roles. and hence rely on geographic data for its implementation

  

Geographic Information System (GIS)

• A computer-based information system that enables capture, modeling, manipulation, retrieval, analysis, and presentation of geographically referenced data

• In simpler terms, GIS is a set of computer-based systems for managing geographic data and using these data to solve real-world spatial problems

• GIS Layers to model the real world

Visualization

• Central to the communication of spatial data

• A representation of our environment

• GIS-based Visualization

  • Advances in computer graphics allowed for these visualizations to become real-time, interactive and very complex

  • Visualization techniques are essential to extract useful information from the large mass of data

  • “In GIS, visualization is used to organize spatial data and related information into layers that can be analyzed or displayed as maps, three-dimensional scenes, summary chart, tables, time-based views, and schematics.” - ESRI

3D Visualization

• Traditional GIS systems are plotted along two dimensions: horizontal (x) and vertical (y) axes

• 3D GIS goes beyond providing coordinates and makes it possible to depict objects in greater detail by adding another dimension (z)

• 3D geographical information is the addition of height, image, attribute information on the geographic information 2D

• 3D GIS Data = 2D GIS Data + height

• Representation of geographic information is similar to the real world

• 3D Visualization Approaches

  • Image Draping

    • the process of projecting a 2D image onto a 3D surface to create a more realistic and detailed visualization of the terrain

  • Geometric Modelling

    • Builds a scene of realistic features

    • Features are modelled more realistically and may closely resemble the appearance of these features as seen in the ground

• 3D Analysis in GIS

  • Line of Sight (LOS)

    • Predicting whether one point is visible from another (intervisibility analysis)

  • Determining line of sight

• Types of 3D Data

  • 3D-surface terrain data

    • Raster: image and grid

    • TIN

    • Represents height values over an area, and the 3D information for each location within that area can be either stored as cell values or deduced from a triangulated network of 3D faces

  • 3D-feature data

    • Shapefile

    • Geodatabase feature class

    • Layer property:

      • base heights - the elevation values that are used to display a layer in 3D

      • extrusion - 3D extension for features

    • Represents discrete objects, and the 3D information for each object is stored in the feature’s geometry

• Types of 3D Models

  • Small Scale Models (Multi-level)

  • Medium Scale Models

  • Large Scale Models - more detailed

• 3D Models: Level of Detail (LoD)

  • LoD 0 - It can be argued that the LoD0 cannot be considered as a 3D city model since it is a boundary representation in 2D with a height as an attribute

  • LoD 1 - with height

  • LoD 2 - with roofings

  • LoD 3 - with detailed architectural features and possibly interior elements

  • LoD 4 - includes detailed information about building materials and furniture layouts

Examples and Applications

• 3D Analysis in GIS

  • Line of Sight (LOS)

  • Visibility Analysis - Viewshed and Observer Points

    • Viewshed Analysis: Determines the visible areas from one or multiple observer points, used for planning and site analysis.

    • Observer Points: Specific locations where visibility calculations are based, crucial for urban planning and landscape assessments.

  • Shadows

  • Watersheds

  • Volume computations

  • Solar Exposure

  • 3D Path Routing

  • 4D (temporal change)

  • Feature Interference

  • Skyline

  • Urban visualization

    • Describes 3D rendering of urban landscapes

    • Corresponds to the use of behavioral or process modeling of the dynamic changes in urban activities and landscapes

  • Constructing 3D Data for City Models

    • Using LiDAR for 3D City Modeling

    • To extract 3D building shapes from lidar data, you’ll first classify the point cloud, identifying the cloud points representing the ground and the buildings of the area of interest

    • UAV data and 3D modelling

  • Indoor GIS

    • Includes any or all of the following:

      • Indoor Mapping

      • Building Information Modelling (BIM)

        • “A model-based technology linked with a database of project information”— American Institute of Architects;

        • 3D, virtual representation of a design project

        • Includes:

          • Geometry

          • Spatial Relationships

          • Geographic Information

          • Quantities

          • Properties of Building Components

      • Indoor Location-based Services (e.g. Indoor Routing and Navigation)