direct georeferencing and orthorectification of airborne digital images a thesis submitted to the

150 Pages·2008·39.68 MB·English

DIRECT GEOREFERENCING AND ORTHORECTIFICATION OF
AIRBORNE DIGITAL IMAGES

A THESIS SUBMITTED TO
THE GRADUATE SCHOOL OF NATURAL AND APPLIED SCIENCES
OF
MIDDLE EAST TECHNICAL UNIVERSITY

BY

ALĐ COŞKUN KĐRACI

IN PARTIAL FULFILLMENT OF THE REQUIREMENTS
FOR
THE DEGREE OF MASTER OF SCIENCE
IN
GEODETIC AND GEOGRAPHIC INFORMATION TECHNOLOGIES

SEPTEMBER 2008
Approval of the thesis:

DIRECT GEOREFERENCING AND ORTHORECTIFICATION OF
AIRBORNE DIGITAL IMAGES

submitted by ALĐ COŞKUN KĐRACI in partial fulfillment of the requirements
for the degree of Master Thesis in Geodetic and Geographic Information
Technologies Department, Middle East Technical University by,

Prof. Dr. Canan Özgen __________________
Dean, Graduate School of Natural and Applied Sciences

Assoc.Prof. Dr. Şebnem Düzgün __________________
Head of Department, Geodetic and Geographic
Information Technologies

Assoc. Prof. Dr. Mahmut Onur Karslıoğlu __________________
Supervisor, Civil Engineering Dept., METU

Examining Committee Members

Prof.Dr. Vedat Toprak __________________
Geological Engineering Dept., METU

Assoc.Prof.Dr. M. Onur Karslıoğlu __________________
Civil Engineering Dept., METU

Prof.Dr. Kerim Demirbaş __________________
Electrical and Electronics Engineering Dept., METU

Assoc.Prof.Dr. Sadık Bakır __________________
Civil Engineering Dept., METU

Erol Tunalı __________________
TÜBĐTAK UZAY
Date: 01.09.2008
I hereby declare that all information in this document has been obtained and
presented in accordance with academic rules and ethical conduct. I also
declare that, as required by these rules and conduct, I have fully cited and
referenced all material and results that are not original to this work.

Name, Last name: Ali Coşkun KĐRACI

Signature :

iii
ABSTRACT

DIRECT GEOREFERENCING AND ORTHORECTIFICATION OF
AIRBORNE DIGITAL IMAGES

Kiracı, Ali Coşkun
M. Sc., Department of Geodetic and Geographic Information Technologies
Supervisor : Assoc.Prof. Mahmut Onur Karslıoğlu

September 2008, 131 pages

GPS/INS (Global Positioning System / Inertial Navigation System) brings
possibility of relaxing the demand for aerial triangulation in stereo model
construction and rectification. In this thesis a differential rectification algorithm is
programmed with Matlab software for aerial frame camera images. This program
is tested using exterior orientation parameters obtained by GPS/INS and images
are ortho-rectified. Ground Control Points (GCP) are measured in the ortho-
rectified images and compared with other rectification methods according to
RMSE and mean error.

Besides, direct georeferencing accuracy is investigated by using GPS/INS data.
Therefore, stereo models and ortho-images are constructed by using exterior
orientation parameters obtained with both aerial triangulation and GPS/INS
integration. GCPs are measured in both stereo models and ortho-images,
compared with respect to their RMSE and mean error. In order to determine
Digital Elevation Model (DEM) effect in ortho-rectification, different DEM data
are used and the results are compared.

Keywords: Direct georeferencing, GPS/INS, orthoimages, orthorectification,
rectification.
iv
ÖZ

HAVADAN ALINAN DĐJĐTAL GÖRÜNTÜLERĐN DOĞRUDAN
YÖNELTĐLMESĐ VE ORTOREKTĐFĐKASYONU

Kiracı, Ali Coşkun
Yüksek Lisans, Jeodezi ve Coğrafi Bilgi Teknolojileri Bölümü
Tez Yöneticisi: Doç. Dr. Mahmut Onur Karslıoğlu

Eylül 2008, 131 sayfa

GPS/INS, stereo model oluşturulmasında ve rektifikasyonda havai nirengi
gereksinimi için esneklik getirmektedir. Bu tezde Matlab yazılımı ile havadan
alınan çerçeve kamera görüntüleri için bir diferensiyel rektifikasyon algoritması
programlandı. Bu program, GPS/INS entegrasyonu ile elde edilen dış yöneltme
parametreleri kullanılarak orto-görüntüler oluşturuldu ve test edildi. Orto-
görüntüler üzerinde Yer Kontrol Noktaları ölçüldü ve diğer rektifikasyon
yöntemleri ile karesel ortalama hataları (KOH) ve ortalama hatalarına göre
karşılaştırıldı.
Bunun yanında, GPS/INS verileri kullanılarak doğrudan yöneltmenin doğruluğu
araştırıldı. Bunun için, hem havai nirengi hem de GPS/INS entegrasyonu ile
edilen dış yöneltme parametreleri kullanılarak stereo modeller ve ortogörüntüler
oluşturuldu. Stereo modeller ve orto-görüntüler üzerinde YKN. ları ölçüldü, KOH
ve ortalama hatalarına göre karşılaştırıldı. Sayısal Yükseklik Modeli (SYM) nin
orto-rektifikasyondaki etkisini belirlemek için farklı SYM verileri kullanıldı ve
sonuçlar karşılaştırıldı.
Anahtar Kelimeler: Doğrudan yöneltme, GPS/INS, orto-görüntü,
ortorektifikasyon, rektifikasyon.

v
To My Wife

vi
ACKNOWLEDGEMENTS

The author would like to thank to his supervisor Assoc. Prof. Mahmut Onur
Karslıoğlu for his guidance, advice, criticism and insight throughout the research.
Thanks to Research Assist.Önder Halis Bettemir for his help in implementing the
DRM algorithm.
The author would like to thank Dr. Oktay Eker for his suggestions and comments.
Thanks to Cert.Eng.Orhan Fırat for his help in deriving ellipsoidal heights and
suggestions for writing the thesis.
Special thanks to Kemal Aygan for his help in the process of aero-triangulation
and operators Đbrahim Akalın, Ayşe Çevik and Nurcan Eroğlu for measurements
of GCP coordinates in stereo models.
Thanks to my father and mother for their support and encouragements.
Finally endless thanks to my wife Meltem Kiracı for her support and
encouragements during the thesis study.

vii
TABLE OF CONTENTS

ABSTRACT.................................................................................................................iv
ÖZ.................................................................................................................................v
ACKNOWLEDGEMENTS........................................................................................vii
TABLE OF CONTENTS...........................................................................................viii
LIST OF TABLES......................................................................................................xii
LIST OF FIGURES ....................................................................................................xv
LIST OF ABBREVIATIONS..................................................................................xviii
CHAPTER
1. INTRODUCTION..............................................................................................1
2. AERIAL TRIANGULATION AND DIRECT GEOREFERENCING.............6
2.1 AERIAL TRIANGULATION.................................................................6
2.2 AERIAL TRIANGULATION METHODS.............................................7
2.2.1 Pool Method....................................................................................8
2.2.2 Serial Method..................................................................................9
2.2.3 Aerial Triangulation Method.........................................................10
2.2.4 Aerial Triangulation Method with Kinematic GPS Support.........11
2.2.5 GPS/IMU Supported Aerial Triangulation Adjustment................12
2.3 GLOBAL POSITIONING SYSTEM (GPS).........................................14
2.3.1 Types of Positioning.....................................................................16
2.3.2 Positioning Errors .........................................................................16
2.3.2.1 Orbital Errors....................................................................17
2.3.2.2 Atmospheric Error.............................................................17
viii
2.3.2.3 Multipath Errors................................................................17
2.3.3 Airborne GPS (AGPS) Control.....................................................18
2.3.4 Base Stations.................................................................................18
2.3.5 Processing GPS Data.....................................................................19
2.3.5.1 Point Positioning...............................................................19
2.3.5.2 Differential Code Phase positioning.................................19
2.3.5.3 Carrier Phase Differential Positioning..............................19
2.4 Inertial Navigation Systems...................................................................22
2.4.1 GPS-Aided Inertial Navigation System........................................23
2.5 Direct Georeferencing............................................................................24
2.5.1 Coordinate Frame Definitions.......................................................25
2.5.2 Mapping with Direct Georeferencing...........................................26
2.5.2.1 Computation of 2 dimensional image vector....................26
2.5.2.2 Compute 3D image vector in IMU body frame................27
2.5.2.3 Resolve Image Vector in Local NED Geographic Frame.31
2.5.2.4 Project the Image Vector to the Ground...........................32
2.5.2.5 Computation of ECEF Coordinates..................................33
2.6 Boresight Calibration.............................................................................36
3. ORTHORECTIFICATION..............................................................................38
3.1 Common Rectification Methods............................................................38
3.1.1 Helmert Transformation................................................................38
3.1.2 Affine Transformation..................................................................38
3.1.3 Pseudo Affine Transformation......................................................39
3.1.4 Projective Transformation.............................................................39
3.1.5 Second Order Conformal Transform............................................40
ix
3.1.6 Polynomial Transformation..........................................................40
3.2 Orthorectification...................................................................................41
3.2.1 Orthorectification Methods...........................................................44
3.2.2 The Role of Exterior Orientation Parameters................................45
3.2.3 The Role of DEM..........................................................................46
3.3 DRM Algorithm for Aerial Frame Cameras..........................................47
3.3.1 Transformation from C to C .....................................................49
IM P
3.3.2 Lens Distortion Corrections..........................................................51
3.3.3 Transformation from C to C ......................................................52
P C
3.3.4 Transformation from C to C ......................................................52
C B
3.3.5 Transformation from C to C ......................................................53
B L
3.3.6 Computation of Intersection Point................................................54
3.3.6.1 Transformation from C to C ..........................................54
L E
3.3.6.2 Atmospheric Refraction Correction..................................58
3.3.6.3 Transformation from C to C ..........................................59
E L
3.3.7 Relief Displacement Correction....................................................61
3.3.8 Transformation from C to C .....................................................63
G M
3.3.9 Resampling....................................................................................66
4. TEST AREA, DATA SETS AND SOFTWARE.............................................67
4.1 The Study Area.........................................................................................67
4.2 Flight Plan and GCPs................................................................................67
4.3 Digital Camera and Image Data................................................................69
4.4 Software....................................................................................................70
4.5 DEM Data.................................................................................................70

x