The document discusses 3D modeling techniques using aerial lidar data. It presents a framework for extracting digital terrain models (DTMs) and reconstructing 3D building models. For DTM extraction, it introduces the Minimum Block Classification model implemented in GIS. For building reconstruction, it describes a process involving generating a TIN, extracting roof patches, detecting planar faces, intersecting roof planes, and final 3D reconstruction. Case studies demonstrate the approaches. The document concludes the techniques can successfully create 3D models from lidar data and that model quality depends on factors like building complexity and point distribution.
Buildings3 d gThe Use of Geographical Information Systems for 3D Urban Models Reconstruction from Aerial Lidar Data
1. 21/4/2015 Dr. Ahmad Yousef
The Use of GIS for 3D Urban Models
Reconstruction Based on Aerial Lidar Data
Dr. Ahmad Yousef
2. 21/4/2015 Dr. Ahmad Yousef
• Overview
• Objectives & Goals
• Digital Terrain Model Extraction
• 3D Building Model Reconstruction
• Conclusion & Final Thoughts
AGENDA
3. 21/4/2015 Dr. Ahmad Yousef
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 …
4. 21/4/2015 Dr. Ahmad Yousef
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 …
8. 21/4/2015 Dr. Ahmad Yousef
Overview
Workshop Objectives & Goals
1. Introduce a fast and simple integrated Digital Terrain Model (DTM)
extraction framework in a GIS environment.
9. 21/4/2015 Dr. Ahmad Yousef
Overview
Workshop Objectives & Goals
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.
10. 21/4/2015 Dr. Ahmad Yousef
Digital Terrain Model Extraction
How to classify lidar data into terrain and off-terrain points?
11. 21/4/2015 Dr. Ahmad Yousef
• 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
12. 21/4/2015 Dr. Ahmad Yousef
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
25. 21/4/2015 Dr. Ahmad Yousef
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 ?
26. 21/4/2015 Dr. Ahmad Yousef
3D Building Model
Buildings Shapes …
Redlands, USA. Source : Google maps
27. 21/4/2015 Dr. Ahmad Yousef
3D Building Model
No Comments …
Venezuela. Barrio Petare, Caracas.
Source: A sustainable approach to problems in urban squatter developments
28. 21/4/2015 Dr. Ahmad Yousef
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
29. 21/4/2015 Dr. Ahmad Yousef
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
30. 21/4/2015 Dr. Ahmad Yousef
3D Building Model
Modeling Approaches
Source: International Summer School “Digital Recording and 3D Modeling”.
3D Building Models Database
Flat Desk Gable Hipped Mansard PyramidGambrel
31. 21/4/2015 Dr. Ahmad Yousef
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”.
32. 21/4/2015 Dr. Ahmad Yousef
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.
33. 21/4/2015 Dr. Ahmad Yousef
3D Building Model
Building Model Elements
Planar Patches
Wall
Footprint
Planar Face
TIN Triangles
Lidar
Roof Boundary
34. 21/4/2015 Dr. Ahmad Yousef
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
38. 21/4/2015 Dr. Ahmad Yousef
3D Building Model
2 - Extract Roof Planar Patches
A.X + B.Y + C.Z + D = 0
N=(A,B,C)
39. 21/4/2015 Dr. Ahmad Yousef
3D Building Model
2 - Extract Roof Planar Patches
Normal Vector Estimation
1 Ring Neighborhood 2 Rings Neighborhood
40. 21/4/2015 Dr. Ahmad Yousef
3D Building Model
2 - Extract Roof Planar Patches
Normal Vector Estimation
41. 21/4/2015 Dr. Ahmad Yousef
3D Building Model
2 - Extract Roof Planar Patches
Normal Vector Estimation
42. 21/4/2015 Dr. Ahmad Yousef
1 Ring Neighborhood
3D Building Model
2 - Extract Roof Planar Patches
Normal Vector Estimation
43. 21/4/2015 Dr. Ahmad Yousef
3D Building Model
2 - Extract Roof Planar Patches
Normal Vector Estimation
2 Rings Neighborhood
44. 21/4/2015 Dr. Ahmad Yousef
2 Rings Neighborhood
3D Building Model
2 - Extract Roof Planar Patches
Normal Vector Estimation
45. 21/4/2015 Dr. Ahmad Yousef
3D Building Model
2 - Extract Roof Planar Patches
Segmentation & Region Growing
Apply region growing to find roof patches
46. 21/4/2015 Dr. Ahmad Yousef
3D Building Model
2 - Extract Roof Planar Patches
Segmentation & Region Growing
47. 21/4/2015 Dr. Ahmad Yousef
3D Building Model
2 - Extract Roof Planar Patches
Segmentation & Region Growing
48. 21/4/2015 Dr. Ahmad Yousef
3D Building Model
2 - Extract Roof Planar Patches
Segmentation & Region Growing
49. 21/4/2015 Dr. Ahmad Yousef
3D Building Model
3 - Detection of Planar Roof Faces
50. 21/4/2015 Dr. Ahmad Yousef
3D Building Model
3 - Detection of Planar Roof Faces
Vertical Triangles
All triangles with slope greater than 60 are
considered as vertical patches
51. 21/4/2015 Dr. Ahmad Yousef
3D Building Model
3 - Detection of Planar Roof Faces
Least Square Plane Fitting
A * X + B * Y + C * Z = D
The Plane Normal is given by : N = (A,B,C)
52. 21/4/2015 Dr. Ahmad Yousef
3D Building Model
3 - Detection of Planar Roof Faces
Intersection of adjacent patches
A * X + B * Y + C * Z = D
53. 21/4/2015 Dr. Ahmad Yousef
3D Building Model
3 - Detection of Planar Roof Faces
Merging Planar Patches
54. 21/4/2015 Dr. Ahmad Yousef
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
55. 21/4/2015 Dr. Ahmad Yousef
3D Building Model
4 - Intersection of Roof Planes
56. 21/4/2015 Dr. Ahmad Yousef
3D Building Model
4 - Intersection of Roof Planes
70. 21/4/2015 Dr. Ahmad Yousef
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.
71. 21/4/2015 Dr. Ahmad Yousef
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.
72. 21/4/2015 Dr. Ahmad Yousef
Thank You
Share What You Can To Benefit The Others
Ahmad Yousef (yousef@dii-eumena.com)