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 ModelsReconstruction Based on Aerial Lidar Data

Dr. Ahmad Yousef


• Overview

• Objectives & Goals

• Digital Terrain Model Extraction

• 3D Building Model Reconstruction

• Conclusion & Final Thoughts

AGENDA


Pollution, CairoVisualization, 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.

OverviewWhy 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 theworld’s population could addanother 2.5 billion people tourban populations by 2050

o 90 percent of the increaseconcentrated in Asia andAfrica

OverviewWhy urban area …


OverviewWhy lidar data …

Waldkirch, Germany


OverviewWorkshop Objectives & Goals





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



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 ExtractionFiltering lidar data


DTM ExtractionEsri Terrain Dataset

Surface geometry at different resolution (TINs)

– TIN is acronym for triangulated irregular network.

Level of Detail-Pyramid

LoD x

Pyramid Type:I. WINDOWSIZEII. ZTOLERANCE

parameter:I. ZMINII. ZMAXIII. ZMEANIV. ZMINMAX










DTM ExtractionMinimum 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





1

2

3

5

Window Size Z-threshold

32 3.2

16 1.6

8 0.8

4 0.4

2 0.2

4





Convert Terrain to TIN

Smoothing

Umbrella Filter


DTM ExtractionDigital Surface Model


DTM ExtractionDigital Terrain Model


Digital Surface Model Shaded Relief

DTM ExtractionForest Dataset …

Digital Terrain Model Shaded Relief


45m x 35m

DTM ExtractionUrban Dataset …

5 750 000 Points


DTM ExtractionUrban 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 ModelBuildings Shapes …

Redlands, USA. Source : Google maps


3D Building ModelNo Comments …

Venezuela. Barrio Petare, Caracas.Source: A sustainable approach to problems in urban squatter developments


3D Building ModelLevel 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 ModelModeling 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



Source: International Summer School “Digital Recording and 3D Modeling”.

3D Building Models Database

Flat Desk Gable Hipped Mansard PyramidGambrel


Data Structure Based – Data Derive


• 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


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 ModelBuilding Model Elements

Planar Patches

Wall

Footprint

Planar Face

TIN Triangles

Lidar

Roof Boundary


5 Processing Steps :-

3D Building ModelFramework …

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 Model1 - Triangle Irregular Network


3D Building Model1 - Triangle Irregular Network


3D Building Model2 - Extract Roof Planar Patches

A.X + B.Y + C.Z + D = 0N=(A,B,C)



Normal Vector Estimation

1 Ring Neighborhood 2 Rings Neighborhood








1 Ring Neighborhood






2 Rings Neighborhood


2 Rings Neighborhood





Segmentation & Region Growing

Apply region growing to find roof patches











3D Building Model3 - Detection of Planar Roof Faces



Vertical Triangles

All triangles with slope greater than 60 are considered as vertical patches



Least Square Plane Fitting

A * X + B * Y + C * Z = D

The Plane Normal is given by : N = (A,B,C)



Intersection of adjacent patches

A * X + B * Y + C * Z = D



Merging Planar Patches


3D Building Model4 - 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 Model5 - 3D Model Reconstruction












3D Building ModelExample 1







Minimum area threshold = 5 m2

Minimum area threshold = 3 m2




3D Building ModelTest Area


3D Building ModelError Sources


SummaryConclusion & 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.


SummaryConclusion & Final Thoughts...

o Minimum Block Classification (MBC) Model was successfully implementedin GIS environment.

o 3D building reconstruction models from lidar data was developed fromconstructing 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 complexbuildings.


Thank YouShare What You Can To Benefit The OthersAhmad Yousef ([email protected])

Engineering

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