Sandau R. Digital Airborne Camera: Introduction and Technology
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Digital Airborne Camera
Introduction and Technology
Edited by
Rainer Sandau
DLR, Berlin, Germany
With contributions by Ulrich Beisl, Bernhard Braunecker, Michael Cramer,
Hans Driescher, Andreas Eckardt, Peter Fricker, Michael Gruber, Stefan Hilbert,
Karsten Jacobsen, Walfried Jagschitz, Herbert Jahn, Werner Kirchhofer, Klaus J.
Neumann, Rainer Sandau, and Maria von Schönermark
1 3
Editor
Dr. Rainer Sandau
Deutsches Zentrum for
Luft- und Raumfahrt e.V.
(DLR)
Rutherfordstr. 2
12489 Berlin
Germany
rainer.sandau@dlr.de
ISBN 978-1-4020-8877-3 e-ISBN 978-1-4020-8878-0
DOI 10.1007/978-1-4020-8878-0
Springer Dordrecht Heidelberg London New York
Library of Congress Control Number: 2009940584
© Springer Science+Business Media B.V. 2010
No part of this work may be reproduced, stored in a retrieval system, or transmitted in any form or by
any means, electronic, mechanical, photocopying, microfilming, recording or otherwise, without written
permission from the Publisher, with the exception of any material supplied specifically for the purpose
of being entered and executed on a computer system, for exclusive use by the purchaser of the work.
Cover illustration: Transparent view of the ADS40 camera made by Leica Geosystems AG.
Printed on acid-free paper
Springer is part of Springer Science+Business Media (www.springer.com)
This is a translation of the book in German “Digitale Luftbildkamera − Einführung und Grundlagen”,
by Rainer Sandau, published by Wichmann Verlag, 2005; including some new additions in chapter 7
(Examples)
Preface
Digital airborne cameras are now penetrating the market of photogrammetry and
remote sensing. Owing to rapid progress in the last 10 years in fields such as detec-
tor technology, computer power, memory capacity, and measurement of position
and orientation, it is now possible to acquire, with the new generation of digital
airborne cameras, different sets of geometric and spectral data with high resolution
within a single flight. This is a decisive advantage over aerial film cameras. The
linear characteristic of the optoelectronic converters is at the root of this transfor-
mation from an imaging camera to a measuring instrument that captures images.
The direct digital processing chain from the airborne camera to the derived prod-
ucts involves no chemical film development or digitisation in a photogrammetric
film scanner. Causes of failure, expensive investments and prohibitive staff costs are
avoided. The effective use of this new technology, however, requires knowledge of
the characteristics, possibilities and restrictions of the formation of images and the
generation of information from them.
This book describes all the components of a digital airborne camera, from the
object to be imaged to the mass memory device on which the imagery is written in
the air. Thus natural processes influencing image quality are considered, such as the
reflection of the electromagnetic energy from the sun by the object being imaged
and the influence of the atmosphere. The essential features and related parame-
ters of the new technology are discussed and placed in a system framework. The
complex interdependencies between the components, for example, optics, filters,
detectors, analogue and digital electronics, and software, become apparent. The
book describes several systems available on the market at the time of writing.
The book will appeal to all who want to be informed about the technology of
the new generation of digital airborne cameras. Groups of potential readers include:
managers who have to decide about investment in and use of the new cameras;
camera operators whose knowledge of the features of the cameras is essential to
the quality of the data acquired; users of derived products who want to order or
effectively process the new digital data sets; and scientists and university students,
in photogrammetry, remote sensing, geodesy, cartography, geospatial and environ-
mental sciences, forestry, agriculture, urban planning, land use monitoring and other
fields, who need to prepare for the use of the new cameras and their imagery.
v
vi Preface
This book is a translation of the publication in German, Digitale
Luftbildkamera − Einführung und Grundlagen, published in 2005 by Herbert
Wichmann Verlag in Heidelberg. Only Chapter 7 was extended to three example
camera systems which are being marketed worldwide and are also roughly represen-
tative of the bandwidth of the implementation variations. I would like to acknowl-
edge Wichmann Verlag’s gracious agreement to transfer the English-language rights
to Springer.
I would like also to acknowledge the help that the contributors to this book
received from a number of individuals:
Ms. Ute Dombrowski (DLR, Berlin, Germany), who was very supportive in typ-
ing large parts of the manuscript, dealing with figures and tables, editing the chapters
of the various authors, and combining the results into a book.
Dr. A. Stewart Walker (BAE Systems, San Diego, USA), who proof-read the
entire manuscript in order to polish and homogenise the usage of the English
language in the translation from German carried out by the authors.
Dipl.-Ing. Dieter Zeuner (formerly Applanix, Toronto, Canada), who contributed
to the translation of the German version.
Prof. Dr.-Ing. Hans-Peter Röser (Unversität Stuttgart, Institut für
Photogrammetrie, Germany; formerly DLR, Berlin, Germany), who led the
DLR team during the joint development of the ADS40 with Leica and LH Systems.
Ms. Petra van Steenbergen of the publisher, who supported the creation of the
book through pleasant, patient collaboration.
Berlin, Germany Rainer Sandau
April 2009
Contents
1 Introduction ............................... 1
1.1 From Analogue to Digital Airborne Cameras . . ........ 1
1.2 Applications for Digital Airborne Cameras
in Photogrammetry and Remote Sensing ............. 8
1.3 Aircraft Camera or Satellite Camera . . ............. 13
1.3.1 Detection, Recognition, Identification . ........ 16
1.4 Matrix Concept or Line Concept ................. 20
1.5 SelectionofCommercialDigitalAirborneCameras....... 27
1.5.1 ADS80.......................... 27
1.5.2 DMC .......................... 29
1.5.3 UltraCam ........................ 29
2 Foundations and Definitions ...................... 31
2.1 Introduction ............................ 31
2.2 Basic Properties of Light . . . .................. 34
2.3 FourierTransforms........................ 41
2.4 Linear Systems . . . ....................... 56
2.5 Sampling ............................. 69
2.6 RadiometricResolutionandNoise................ 78
2.7 Colour .............................. 89
2.8 Time Resolution and Related Properties ............. 95
2.9 ComparisonofFilmandCCD.................. 99
2.9.1 Comparison of the Imaging Process and the
CharacteristicCurve................... 99
2.9.2 Sensitivity . ....................... 101
2.9.3 Noise .......................... 102
2.9.4 Signal to Noise Ratio (SNR) . ............. 102
2.9.5 Dynamic Range . . . .................. 103
2.9.6 MTF........................... 104
2.9.7 MTF · Snr........................ 104
2.9.8 Stability of Calibration ................. 105
2.9.9 Spectral Range . . . .................. 106
2.9.10 Summary ........................ 107
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viii Contents
2.10 Sensor Orientation . ....................... 107
2.10.1 Georeferencing of Sensor Data ............. 107
2.10.2 Brief Review of GVP Concepts GPS . . ........ 116
2.10.3 BasicsofInertialNavigation .............. 121
2.10.4 Concepts of Inertial/GPS Integration . . ........ 128
3 The Imaged Object and the Atmosphere ............... 131
3.1 Radiation in Front of the Sensor ................. 131
3.2 Radiation at the Sensor ...................... 134
3.3 Contrast of a Scene at the Sensor ................. 137
3.4 Bi-directional Reflectance Distribution Function BRDF . .... 138
4 Structure of a Digital Airborne Camera ............... 143
4.1 Introduction ............................ 143
4.1.1 Example......................... 149
4.2 Optics and Mechanics ...................... 151
4.2.1 EffectofGeometry ................... 151
4.2.2 TheEffectoftheWaveNatureofLight......... 153
4.2.3 Space-Bandwidth Product . . . ............. 153
4.2.4 PrincipalRays...................... 154
4.2.5 Physical Imaging Model . . . ............. 154
4.2.6 Data Transfer Rate of High Performance
OpticalSystem ..................... 155
4.2.7 Camera Constant and “Pinhole” Model . ........ 156
4.2.8 Pupil Characteristics .................. 157
4.2.9 Design and Manufacturing Aspects . . . ........ 159
4.2.10 Summary of the Geometric Properties of an Image . . . 160
4.2.11 AberrationsandPrecisionofRegistration ....... 169
4.2.12 RadiometricCharacteristics............... 171
4.2.13 Ideal Optical Transfer Function ............. 172
4.2.14 Real Optical Transfer Function ............. 175
4.2.15 Field Dependency of the Optical Transfer Function . . 177
4.3 Filter . . . ............................ 180
4.3.1 Absorption Filters . . .................. 180
4.3.2 Interference Filters . .................. 183
4.4 Opto-ElectronicConverters ................... 183
4.4.1 OperatingPrinciple ................... 184
4.4.2 CCDArchitectures ................... 188
4.4.3 Properties and Parameters . . . ............. 196
4.5 Focal Plane Module ....................... 210
4.5.1 Basic Structure of a Focal Plane Module ........ 210
4.6 Up-Front Electronic Components . . . ............. 212
4.6.1 CCDControl ...................... 213
4.6.2 Signal Pre-Processing .................. 215
4.6.3 Analogue-Digital Conversion . ............. 217
4.7 DigitalComputer......................... 221
Contents ix
4.7.1 TheControlComputer ................. 221
4.7.2 DataCompression.................... 227
4.7.3 DataMemory/DataStorage............... 231
4.8 Flight Management System . .................. 232
4.8.1 Flight Planning . . . .................. 233
4.8.2 FlightEvaluation .................... 234
4.8.3 FlightExecution..................... 234
4.8.4 OperatorandPilotInterface............... 236
4.8.5 Operator Concept . . .................. 237
4.9 System for Measurement of Position and Attitude ........ 238
4.9.1 GPS/IMU System in Operational Use . ........ 238
4.9.2 Integration of GPS/IMU Systems with Imaging Sensors 245
4.10 Camera Mount . . . ....................... 250
4.10.1 Rigid Mount ....................... 250
4.10.2 Frequency Spectrum in Aircraft and MTF . . . .... 250
4.10.3 Uncontrolled Camera Mount . ............. 257
4.10.4 Controlled Camera Mount . . ............. 258
5 Calibration ............................... 261
5.1 GeometricCalibration ...................... 261
5.2 Determination of Image Quality ................. 267
5.3 RadiometricCalibration ..................... 268
6 Data Processing and Archiving .................... 273
7 Examples of Large-Scale Digital Airborne Cameras ......... 279
7.1 The ADS40 System: A Multiple-Line Sensor
for Photogrammetry and Remote Sensing ............ 279
7.1.1 Introduction ....................... 279
7.1.2 TheDigitalControlUnit ................ 286
7.1.3 Sensor Management . .................. 290
7.1.4 The Flight Planning and Navigation Software . .... 292
7.1.5 The Position and Attitude Measurement System .... 293
7.1.6 The Gyro Stabilized Mount for the ADS40 . . . .... 294
7.1.7 TheRadiometricundGeometricCalibration...... 295
7.1.8 DataProcessing..................... 297
7.1.9 Images Acquired with the ADS40 . . . ........ 299
7.2 Intergraph DMC Digital Mapping Camera ............ 307
7.2.1 Introduction ....................... 307
7.2.2 LensCone–BasicDesignoftheDMC......... 308
7.2.3 Innovative Shutter Technology ............. 309
7.2.4 CCD Sensor and Forward Motion
Compensation . . . .................. 309
7.2.5 DMCRadiometricResolution ............. 311
7.2.6 DMC Airborne System Configuration . ........ 311
7.2.7 System Calibration and Photogrammetric Accuracy . . 312
x Contents
7.3 UltraCam, Digital Large Format Aerial Frame Camera System . 313
7.3.1 Introduction ....................... 313
7.3.2 UltraCamX Produces the Largest Format
Digital Frame Images .................. 314
7.3.3 UltraCam Design Concept . . ............. 317
7.3.4 GeometricCalibration.................. 320
7.3.5 Geometric Accuracy at the 1 μmLevel......... 323
7.3.6 Radiometric Quality and Multispectral Capability . . . 327
7.3.7 ThePotentialofDigitalFrameCameras ........ 328
7.3.8 Microsoft Photogrammetry . . ............. 329
Abbreviations ................................ 333
Bibliography ................................. 335
Index ..................................... 341
Contributors
Editor
Dr. Rainer Sandau
List of Authors
Dr. Ulrich Beisl Section
Leica Geosystems AG, Heerbrugg, Switzerland 2.9
Dr. Bernhard Braunecker
Leica Geosystems AG, Heerbrugg, Switzerland 4.2, 4.3
Dr. Michael Cramer
Universität Stuttgart, Institut für Photogrammetrie, Stuttgart, Germany 2.10, 4.9
Dr. Hans Driescher
Deutsches Zentrum für Luft- und Raumfahrt (DLR), Berlin, Germany 4.5
Dr. Andreas Eckardt
Deutsches Zentrum für Luft- und Raumfahrt (DLR), Berlin, Germany 2.8
Dipl.-Ing. Peter Fricker
Leica Geosystems AG, Heerbrugg, Switzerland 7.1
Dr. Michael Gruber
Microsoft Photogrammetry, Graz, Austria 7.3
Dipl.-Ing. Stefan Hilbert
Deutsches Zentrum für Luft- und Raumfahrt (DLR), Berlin, Germany 4.4, 4.6
Dr. Karsten Jacobsen
Leibniz Universität Hannover, Institut für Photogrammetrie und
GeoInformation, Hannover, Germany 2.10
Dipl.-Ing. Walfried Jagschitz
Leica Geosystems AG, Heerbrugg, Switzerland 4.10
xi
xii Contributors
Prof. Dr. Herbert Jahn
Deutsches Zentrum für Luft- und Raumfahrt (DLR), Berlin, Germany 2,
2.1−2.7
Dipl.-Ing. Werner Kirchhofer
Leica Geosystems AG, Heerbrugg, Switzerland 4.7, 4.8
Dipl.-Ing. Klaus J. Neumann
Intergraph AG, Aalen, Germany 7.2
Dr. Rainer Sandau
Deutsches Zentrum für Luft- und Raumfahrt (DLR),
Berlin, Germany 1, 4,
4.1–4.3,
4.10, 7
Dr. Maria von Schönermark
Universität Stuttgart, Institut für Raumfahrtsysteme, Germany 3
Dipl.-Ing. Udo Tempelmann
Leica Geosystems AG, Heerbrugg, Switzerland 5, 6