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MODELING 3D BUILDINGS OF LOD2 FROM AIRBORNE POINT CLOUD USING UNSUPERVISED CLASSIFICATION SETHU MADHAVAN JANARTHANAN A project report submitted in partial fulfillment of the requirements for the award of the degree of Master of Science (Geoinformatics) Faculty of Geoinformation and Real Estate Universiti Teknologi Malaysia AUGUST 2011
Transcript

MODELING 3D BUILDINGS OF LOD2 FROM AIRBORNE POINT CLOUD USING

UNSUPERVISED CLASSIFICATION

SETHU MADHAVAN JANARTHANAN

A project report submitted in partial fulfillment of the

requirements for the award of the degree of

Master of Science (Geoinformatics)

Faculty of Geoinformation and Real Estate

Universiti Teknologi Malaysia

AUGUST 2011

iii

ACKNOWLEDGEMENT

It is my great privilege to express gratitude to my supervisor Prof. Dr. Alias

Abdul Rahman, 3D GIS Research Lab and Dean of Faculty of Geoinformation and Real

Estate for giving me the freedom to do my work at my own pace. I am deeply beholden

for the constant encouragement and support to bring out my ideas and channelize them.

I am extremely thankful to Mr. Alex Rixon, Production Manager, AAM Group,

Kuala Lumpur for helping me in this study by giving the data, software and his valuable

ideas and allowing me to work in his office. I would also like to thank Mr. Ahmad

Syuwari at AAM for helping me with the technical issues.

I wish my deep sense of gratitude to all the members of the 3D GIS Research

Group for their support and sharing thoughts throughout my study. I would also like to

thank the staff members of the Faculty of Geoinformation and Real Estate for their help

and assistance. I would like to thank Wasiu, Toyin and all my postgraduate classmates

and friends for their constant encouragement and support in one way or the other

throughout my study.

Finally, I wish to express my heartfelt gratitude and love to my Mom, Dad and

Brother for being with me right through my work and helping me in all possible ways.

iv

ABSTRACT

A variety of applications utilize 2D data in some form or the other to complete

their tasks. But we are living in a 3D world and in most cases 2D information is not

sufficient. Today the need for 3D Geoinformation has increased rapidly mainly because

there is a significant improvement in maintaining, processing and visualizing these data.

A variety of applications have been introduced in relation to visualization like a 3D city

model. A 3D city model includes buildings, vegetation, street furniture and other city

objects. 3D city models can be generated from various sources of data like aerial

images, CAD, satellite imagery, LiDAR and terrestrial laser scan. But LiDAR and

terrestrial laser scan holds as the best source of data in terms of accuracy. With LiDAR

accurate 3D models can be generated when compared to other conventional method like

the photogrammetric technique. The data is collected as set of points called as point

cloud. MicroStation with extension TerraScan was used to process these 3D point

clouds from which the 3D models and the 3D surface model (DTM) were generated.

This study aims to generate 3D city model from the airborne LiDAR and incorporate

them in CityServer3D where the 3D geodatabase is created. All the generated models

are based on the standard CityGML format. Each building is given an external code

based on the CityGML format defined by the Open Geospatial Consortium (OGC). The

models inside the CityServer3D can be visualized as well as queried. The Level of

Detail of the 3D models is restricted to 2 without façade textures. This 3D city model

will be of good use to the local authorities of Miri during times of flood because the

study area is located relatively close to a river meeting the sea. This 3D city model can

be improved by adding textures, increasing the level of detail which will be more virtual

and realistic.

v

ABSTRAK

Pada masa kini, terdapat pelbagai aplikasi di dalam bentuk 2D digunakan di

dalam menyelesaikan tugasan. Bagaimanapun, maklumat di dalam bentuk 2D sahaja

tidak mencukupi memandangkan persekitaran di sekeliling berbentuk 3D. Kini,

keperluan kepada geoinformasi berbentuk 3D telah meningkat kerana keupayaannya di

dalam mengekalkan, memproses dan menggambarkan sesebuah data. Pelbagai aplikasi

telah diperkenalkan di dalam menvisualisasikan sesebuah bandar di dalam bentuk 3D.

Model 3D bandar termasuklah bangunan, tumbuhan, perabot jalan dan objek bandar

yang lain. Model 3D bandar boleh dijana daripada pelbagai sumber data seperti imej

udara, CAD, imej satelit, LiDAR dan imbasan terrestrial laser. Bagaimanapun sumber

dari LiDAR dan imbasan terrestrial laser lebih tepat dan jitu. Model 3D yang dihasilkan

dari LiDAR lebih tepat berbanding menggunakan kaedah konvensional seperti teknik

fotogrametri. Set data yang dikumpul dikenali sebagai titik awan. Microstation dengan

sambungan TerraScan digunakan di dalam proses 3D titik awan ini di mana model 3D

dan permukaan 3D (DTM) akan dihasilkan. Kajian ini bertujuan untuk menjana model

3D bandar berasaskan data LIDAR udara dan menggabungkan data menggunakan

perisian CityServer3D di mana akan membentuk geodatabase bagi model 3D. Model-

model yang dihasilkan adalah mengikut piawaian dan format CityGML. Setiap

bangunan akan dinamakan dengan kod luar berdasarkan format CityGML yang

ditakrifkan oleh Open Geospatial Consortium (OGC). Model yang dihasilkan dari

CityServer3D boleh digambarkan dan tahap perincian model 3D yang dihasilkan terhad

kepada dua permukaan iaitu hadapan dan tekstur bangunan. Penghasilan model 3D ini

seterusnya dapat membantu Pihak Berkuasa Tempatan Miri di dalam mengatasi masalah

banjir kerana kawasan kajian terletak berhampiran dengan muara sungai. Model 3D

bandar ini boleh diperbaiki dengan menambah tekstur, bagi meningkatkan tahap

perincian agar model yang dihasilkan lebih realistik.

vi

TABLE OF CONTENTS

CHAPTER TITLE PAGE

TITLE i

DECLARATION ii

ACKNOWLEDGEMENTS iii

ABSTRACT iv

ABSTRAK v

TABLE OF CONTENTS vi

LIST OF FIGURES x

LIST OF ABBREVIATIONS xi

1. INTRODUCTION 1

1.1 General Introduction 1

1.1.1 Visualization 3

1.1.2 3D GIS 4

1.2 Background 6

1.3 Problem Statement 8

1.4 Aim 8

1.5 Objectives 9

1.6 Scope 9

vii

1.6.1 Study Area 9

1.6.2 Data 10

1.6.3 Software 11

1.7 Significance 12

1.8 Chapter Organization 12

2. LITERATURE REVIEW 14

2.1 Introduction 14

2.2 Overview of 3D City Modeling 15

2.3 CityGML 16

2.3.1 CityGML Features 17

2.3.2 Background 18

2.3.3 Level of Detail (LoD) 19

2.4 LIDAR 21

2.5 Terrestrial Laser Scanner 26

2.6 3D City and Urban Modeling 29

2.6.1 City Objects 29

2.6.2 Buildings 30

2.7 MicroStation 31

2.7.1 TerraScan 31

2.7.1.1 Filtering the Point Cloud 32

2.7.1.2 Project and Macros 33

2.7.1.3 Features 33

2.8 Google SketchUp 35

2.9 CityServer3D 36

2.10 Google Earth 36

2.10.1 Buildings in 3D 37

2.11 Softwares for working with LiDAR data 37

2.12 Related Works 40

viii

2.13 Summary 43

3. METHODOLOGY 44

3.1 Introduction 44

3.2 Project Methodology 44

3.3 Data Processing Stage 46

3.3.1 Data Pre-processing 47

3.3.1.1 Noise Filtering 47

3.3.2 Data Post-processing 48

3.4 Data Classification 49

3.5 Data Modeling 51

3.5.1 Generating Surface Model (DTM) 52

3.5.1.1 Accuracy of the DTM 54

3.5.2 Reconstruction of 3D building 56

3.6 Data Visualization 57

3.6.1 Exporting models into CityGML 58

3.6.2 Models inside CityServer3D 59

3.7 Summary 60

4. RESULTS AND DISCUSSION 61

4.1 Introduction 61

4.2 Analyzing the models generated from

MicroStation 61

4.2.1 3D Building Models 62

4.3 Models inside Google Earth 64

4.4 Models inside CityServer3D 64

4.5 Recommendation 66

ix

4.6 Summary 66

5. CONCLUSION AND RECOMMENDATION 67

5.1 Introduction 67

5.2 Conclusion 67

5.3 Problems and Limitations 68

5.4 Recommendation 69

REFERENCES 70

x

LIST OF FIGURES

FIGURE NO TITLE PAGE

Figure 1.1 Study area- Satellite image of part of the Miri City 10

Figure 1.2 LiDAR point cloud of the study area-Miri 11

Figure 2.1 The five levels of detail (LOD) defined by CityGML 20

Figure 2.2 Airborne LiDAR system 23

Figure 2.3 Example of an airborne point cloud 24

Figure 2.4 Example of a terrestrial point cloud 27

Figure 3.1 The Project workflow 45

Figure 3.2 Point cloud data of Miri city 46

Figure 3.3 Noise data 48

Figure 3.4 Noise removed data 48

xi

Figure 3.5 Data classification method 50

Figure 3.6 Segmented point cloud data 51

Figure 3.7 Triangular mesh of the point cloud 53

Figure 3.8 Surface model of the DTM 53

Figure 3.9 Cross-section view of the 3D model with DTM 54

Figure 3.10 Test point results 55

Figure 3.11 Connecting edge segments 56

Figure 3.12 Final model 56

Figure 3.13 Connected edge segments resulting in 3D models 56

Figure 3.14 The complete model in Google SketchUp 57

Figure 3.15 CityGML file as seen in CityGML editor 58

Figure 3.16 3D building models (LoD2) inside CityServer3D 59

Figure 3.17 Adding metadata for a building 59

Figure 3.18 External code list for building class type 60

Figure 4.1 Generated 3D building model overlaid on top

of the point cloud 62

xii

Figure 4.2 LiDAR point cloud of the study area 63

Figure 4.3 Generated 3D model of the study area 63

Figure 4.4 3D city model of Miri inside Google Earth 64

Figure 4.5 3D city model of Miri inside CityServer3D 65

Figure 4.6 CityGML file of a building model 65

xiii

LIST OF ABBREVIATIONS

2.5D - Two-and-a-half-dimensional

2D - Two-dimensional

3D - Three-dimensional

ALDPAT - Airborne LIDAR Data Processing and Analysis Tool

ALS - Airborne Laser Scanning

B-REP - Boundary Representation

CAD - Computer Aided Design

CSG - Constructive Solid Geometry

DBM - Digital Building Model

DEM - Digital Elevation Model

DSM - Digital Surface Model

DTM - Digital Terrain Model

GIS - Geographic Information System

GML - Geographic Markup Language

GPS - Global Positioning System

INS - Inertial Navigation Sensor

LIDAR - Light Detection And Ranging

LoD - Level of Detail

OGC - Open Geospatial Consortium

TIN - Triangulated Irregular Network

TLS - Terrestrial Laser Scanning

USDA - United States Department of Agriculture

USGS - United States Geological Survey

xiv

VRML - Virtual Reality Markup Language

W3DS - Web 3D Service

WGS - World Geodetic System

vi

TABLE OF CONTENTS

CHAPTER TITLE PAGE

TITLE i

DECLARATION ii

ACKNOWLEDGEMENTS iii

ABSTRACT iv

ABSTRAK v

TABLE OF CONTENTS vi

LIST OF FIGURES x

LIST OF ABBREVIATIONS xi

1. INTRODUCTION 1

1.1 General Introduction 1

1.1.1 Visualization 3

1.1.2 3D GIS 4

1.2 Background 6

1.3 Problem Statement 8

1.4 Aim 8

1.5 Objectives 9

1.6 Scope 9

vii

1.6.1 Study Area 9

1.6.2 Data 10

1.6.3 Software 11

1.7 Significance 12

1.8 Chapter Organization 12

2. LITERATURE REVIEW 14

2.1 Introduction 14

2.2 Overview of 3D City Modeling 15

2.3 CityGML 16

2.3.1 CityGML Features 17

2.3.2 Background 18

2.3.3 Level of Detail (LoD) 19

2.4 LIDAR 21

2.5 Terrestrial Laser Scanner 26

2.6 3D City and Urban Modeling 29

2.6.1 City Objects 29

2.6.2 Buildings 30

2.7 MicroStation 31

2.7.1 TerraScan 31

2.7.1.1 Filtering the Point Cloud 32

2.7.1.2 Project and Macros 33

2.7.1.3 Features 33

2.8 Google SketchUp 35

2.9 CityServer3D 36

2.10 Google Earth 36

2.10.1 Buildings in 3D 37

2.11 Softwares for working with LiDAR data 37

2.12 Related Works 40

viii

2.13 Summary 43

3. METHODOLOGY 44

3.1 Introduction 44

3.2 Project Methodology 44

3.3 Data Processing Stage 46

3.3.1 Data Pre-processing 47

3.3.1.1 Noise Filtering 47

3.3.2 Data Post-processing 48

3.4 Data Classification 49

3.5 Data Modeling 51

3.5.1 Generating Surface Model (DTM) 52

3.5.1.1 Accuracy of the DTM 54

3.5.2 Reconstruction of 3D building 56

3.6 Data Visualization 57

3.6.1 Exporting models into CityGML 58

3.6.2 Models inside CityServer3D 59

3.7 Summary 60

4. RESULTS AND DISCUSSION 61

4.1 Introduction 61

4.2 Analyzing the models generated from

MicroStation 61

4.2.1 3D Building Models 62

4.3 Models inside Google Earth 64

4.4 Models inside CityServer3D 64

4.5 Recommendation 66

ix

4.6 Summary 66

5. CONCLUSION AND RECOMMENDATION 67

5.1 Introduction 67

5.2 Conclusion 67

5.3 Problems and Limitations 68

5.4 Recommendation 69

REFERENCES 70

x

LIST OF FIGURES

FIGURE NO TITLE PAGE

Figure 1.1 Study area- Satellite image of part of the Miri City 10

Figure 1.2 LiDAR point cloud of the study area-Miri 11

Figure 2.1 The five levels of detail (LOD) defined by CityGML 20

Figure 2.2 Airborne LiDAR system 23

Figure 2.3 Example of an airborne point cloud 24

Figure 2.4 Example of a terrestrial point cloud 27

Figure 3.1 The Project workflow 45

Figure 3.2 Point cloud data of Miri city 46

Figure 3.3 Noise data 48

Figure 3.4 Noise removed data 48

xi

Figure 3.5 Data classification method 50

Figure 3.6 Segmented point cloud data 51

Figure 3.7 Triangular mesh of the point cloud 53

Figure 3.8 Surface model of the DTM 53

Figure 3.9 Cross-section view of the 3D model with DTM 54

Figure 3.10 Test point results 55

Figure 3.11 Connecting edge segments 56

Figure 3.12 Final model 56

Figure 3.13 Connected edge segments resulting in 3D models 56

Figure 3.14 The complete model in Google SketchUp 57

Figure 3.15 CityGML file as seen in CityGML editor 58

Figure 3.16 3D building models (LoD2) inside CityServer3D 59

Figure 3.17 Adding metadata for a building 59

Figure 3.18 External code list for building class type 60

Figure 4.1 Generated 3D building model overlaid on top

of the point cloud 62

xii

Figure 4.2 LiDAR point cloud of the study area 63

Figure 4.3 Generated 3D model of the study area 63

Figure 4.4 3D city model of Miri inside Google Earth 64

Figure 4.5 3D city model of Miri inside CityServer3D 65

Figure 4.6 CityGML file of a building model 65

xiii

LIST OF ABBREVIATIONS

2.5D - Two-and-a-half-dimensional

2D - Two-dimensional

3D - Three-dimensional

ALDPAT - Airborne LIDAR Data Processing and Analysis Tool

ALS - Airborne Laser Scanning

B-REP - Boundary Representation

CAD - Computer Aided Design

CSG - Constructive Solid Geometry

DBM - Digital Building Model

DEM - Digital Elevation Model

DSM - Digital Surface Model

DTM - Digital Terrain Model

GIS - Geographic Information System

GML - Geographic Markup Language

GPS - Global Positioning System

INS - Inertial Navigation Sensor

LIDAR - Light Detection And Ranging

LoD - Level of Detail

OGC - Open Geospatial Consortium

TIN - Triangulated Irregular Network

TLS - Terrestrial Laser Scanning

USDA - United States Department of Agriculture

USGS - United States Geological Survey

xiv

VRML - Virtual Reality Markup Language

W3DS - Web 3D Service

WGS - World Geodetic System

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