Buildings3 d gThe Use of Geographical Information Systems for 3D Urban Models Reconstruction from Aerial Lidar Data

21/4/2015 Dr. Ahmad Yousef
The Use of GIS for 3D Urban Models
Reconstruction Based on Aerial Lidar Data
Dr. Ahmad Yousef

• Overview
• Objectives & Goals
• Digital Terrain Model Extraction
• 3D Building Model Reconstruction
• Conclusion & Final Thoughts
AGENDA

Pollution, Cairo
Visualization, Dubai
Pollution, Moscow
Flood, Pakistan
Visualization, Los Angeles
City Planning, Stuttgart
Flood, Mexico
• GIS has traditionally been 2D technology.
• New product and technology make us reconsider the role of 3D.
• It is widely recognized that 3D models are necessary.
Overview
Why 3D GIS …

Year : 2050
66%
Year : 2014
54%
Urban Population
World
Source: UN DESA’s Population Division
of Global Population
o The overall growth of the
world’s population could add
another 2.5 billion people to
urban populations by 2050
o 90 percent of the increase
concentrated in Asia and
Africa
Overview
Why urban area …

Overview
Why lidar data …
Waldkirch, Germany

Overview
Workshop Objectives & Goals

Overview
1. Introduce a fast and simple integrated Digital Terrain Model (DTM)
extraction framework in a GIS environment.

Overview
1. Introduce a fast and simple integrated Digital Terrain Model (DTM)
extraction framework in a GIS environment.
2. Introduce a developed GIS approach for reconstructing of the 3D building
models from lidar point clouds.

Digital Terrain Model Extraction
How to classify lidar data into terrain and off-terrain points?

• Filtering means classification of points into terrain and off-terrain.
• Bare earth is assumed to be continuous surface.
• Filtering In/Out data:
– Point list
– Grid
– Triangulated Irregular Network - TIN
DTM Extraction
Filtering lidar data

DTM Extraction
Esri Terrain Dataset
Surface geometry at different resolution (TINs)
– TIN is acronym for triangulated irregular network.
Level of Detail-Pyramid
LoD x
Pyramid Type:
I. WINDOWSIZE
II. ZTOLERANCE
parameter:
I. ZMIN
II. ZMAX
III. ZMEAN
IV. ZMINMAX

DTM Extraction
Esri Terrain Dataset

DTM Extraction
Minimum Block Classification - MBC
Window Block
Bare Earth Surface
Input Points Dataset [Geodatabase], Input Window Size, Cell Size (≈ Points Average Distance)
Output Ground Points, DTM
Window Block

DTM Extraction
1
2
3
5
Window Size Z-threshold
32 3.2
16 1.6
8 0.8
4 0.4
2 0.2
4

DTM Extraction
Convert Terrain to TIN
Smoothing
Umbrella Filter

DTM Extraction
Digital Surface Model

DTM Extraction
Digital Terrain Model

Digital Surface Model Shaded Relief
DTM Extraction
Forest Dataset …
Digital Terrain Model Shaded Relief

45m x 35m
DTM Extraction
Urban Dataset …
5 750 000 Points

DTM Extraction
Urban Dataset …

3D Building Models Reconstruction
How to fulfill the gap between lidar data and building models ?
How to minimize the number of points that represent a building ?

3D Building Model
Buildings Shapes …
Redlands, USA. Source : Google maps

3D Building Model
No Comments …
Venezuela. Barrio Petare, Caracas.
Source: A sustainable approach to problems in urban squatter developments

3D Building Model
Level of Details LoD
• Building model is the representation
used for describing the form of
building.
• The complexity of a 3D building model
is known as the level of details (LoDs).
Source: : Open Geospatial Consortium CityGML Implementation Specification 1.0,20.8 2008
Level of Details
Data Processing
LoD 1 : Flat Roofs
LoD 2 : Roof Type
LoD 3 : Real Roof Shape
LoD 4 : Interior

Model Structure Based – Model Derive
3D Building Model
Modeling Approaches
• Model Database.
• The final roof shape is always topologically correct.
• Complex roof shapes cannot be reconstructed.
3D Building Models Database
Flat Desk Gable Hipped Mansard PyramidGambrel

3D Building Model
Modeling Approaches
Source: International Summer School “Digital Recording and 3D Modeling”.
3D Building Models Database
Flat Desk Gable Hipped Mansard PyramidGambrel

Data Structure Based – Data Derive
3D Building Model
Modeling Approaches
• Roof described by planar faces.
• Partitioning the given ground plan and find the most appropriate plane
segment to each partition.
Source: International Summer School “Digital Recording and 3D Modeling”.

Input for Data Derive Model
3D Building Model
Modeling Approaches
I. Points based
– Points may belong to several planes.
II. Raster based
– Information content is decreased due to interpolation.
III. TIN based
– To avoid loss of information due to interpolation, all operations are performed
on the Delaunay triangulation of the original height points.
– Requires more analysis.

3D Building Model
Building Model Elements
Planar Patches
Wall
Footprint
Planar Face
TIN Triangles
Lidar
Roof Boundary

5 Processing Steps :-
3D Building Model
Framework …
1. Generate Triangle Irregular Network - TIN
2. Extract Roof Planar Patches
i. Normal Vector Estimation
ii. Segmentation & Region Growing
3. Detection of Planar Roof Faces
i. Least Square Plane Fitting
ii. Merging Planar Patches
4. Intersection of Roof Planes
5. 3D Model Reconstruction

3D Building Model
1 - Triangle Irregular Network

3D Building Model
2 - Extract Roof Planar Patches
A.X + B.Y + C.Z + D = 0
N=(A,B,C)

3D Building Model
Normal Vector Estimation
1 Ring Neighborhood 2 Rings Neighborhood

3D Building Model

1 Ring Neighborhood
3D Building Model

3D Building Model
2 Rings Neighborhood

2 Rings Neighborhood
3D Building Model

3D Building Model
Segmentation & Region Growing
Apply region growing to find roof patches

3D Building Model
Segmentation & Region Growing

3D Building Model
3 - Detection of Planar Roof Faces

3D Building Model
Vertical Triangles
All triangles with slope greater than 60 are
considered as vertical patches

3D Building Model
Least Square Plane Fitting
A * X + B * Y + C * Z = D
The Plane Normal is given by : N = (A,B,C)

3D Building Model
Intersection of adjacent patches
A * X + B * Y + C * Z = D

3D Building Model
Merging Planar Patches

3D Building Model
4 - Intersection of Roof Planes
Patch 1 2 3 4 5 6 7
1 YES YES YES YES
2 YES YES YES
3 YES YES
4 YES YES
5 YES YES
6 YES YES YES
7 YES
Plane Adjacency Matrix

3D Building Model
4 - Intersection of Roof Planes

3D Building Model
5 - 3D Model Reconstruction

3D Building Model
Example 1

3D Building Model
Example 2
Minimum area
threshold = 5 m2
Minimum area
threshold = 3 m2

3D Building Model
Example 3

3D Building Model
Test Area

3D Building Model
Error Sources

Summary
Conclusion & Final Thoughts...
• Minimum Block Classification (MBC) Model was successfully implemented
in GIS environment.
• Advantages of MBC Model includes :
– Fixed number of processing loops.
– Capable of capturing and removing the major terrain features.
– Although building size and shape present a challenge for many other filtering
algorithms, they do not significantly hinder the MBC algorithm when using the
proper window size and threshold.

Summary
Conclusion & Final Thoughts...
o Minimum Block Classification (MBC) Model was successfully implemented
in GIS environment.
o 3D building reconstruction models from lidar data was developed from
constructing a roof surface geometry.
o 3D building reconstruction models result affected by
 Minimum area threshold
 Points distribution
 Shape complexity
o The processing time varies and is dependent on the shape of the building,
start from 5 seconds for simple buildings to 30 seconds for complex
buildings.

Thank You
Share What You Can To Benefit The Others
Ahmad Yousef (yousef@dii-eumena.com)

Buildings3 d gThe Use of Geographical Information Systems for 3D Urban Models Reconstruction from Aerial Lidar Data

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