EUROSDR NETWORK ON DIGITAL CAMERA CALIBRATION 
M. Cramer 
Institute for Photogrammetry (ifp), University of Stuttgart, Geschwister-Scholl-Straße 24 D, 70174 Stuttgart / Germany, 
michael.cramer@ifp.uni-stuttgart.de 
KEY WORDS: Camera calibration, digital airborne sensor, network, photogrammetry 
ABSTRACT: 
This paper documents the status of the actual Phase ! of the EuroSDR project on "Digital Camera Calibration". This project was 
officially installed in October 2003 during the 103" EuroSDR Science and Steering Committee Meetings. Up to now about 35 
experts from industry, camera manufacturers, software developers, research and system users already joined this calibration network. 
Some general remarks on the objectives of the project are given in the introductory part of the paper. Besides that, the paper is 
mainly based on the detailed Phase | report describing current practice and methods for digital airborne camera calibration. 
Therefore three airborne sensors already in operational use are chosen exemplarily: The Applanix/Emerge DSS as one representative 
of medium format sensors, and the well-known Zl-Imaging DMC and Leica ADS40 systems, where the latter two both claim to 
replace the standard analogue airborne frame cameras in near future. The different applied calibration approaches and process steps 
are described in the second part of the paper. 
1. INTRODUCTION 
The need of camera calibration is a fundamental requirement in 
the field of photogrammetric data processing. For airborne 
sensors this calibration is typically realized under well 
controlled laboratory conditions, where especially designed 
calibration setups are used to determine the internal camera 
characteristics with sufficient accuracy. From such calibration 
facilities (i.e. multi-collimator or goniometer) the camera 
distortion parameters are estimated using the obtained 
discrepancies between measured coordinates or angles versus 
their a priori known values. Besides this, the focal length and 
principle point coordinates are chosen to minimize the absolute 
amount of lens distortions and to realize a symmetric distortion 
pattern. 
However, this classical situation changes with the increasing 
availability of new digital airborne imaging systems, mainly due 
to the following two aspects: Comparing digital sensor systems 
from their system design concepts, there are large variations 
within the specific system realizations and in comparison with 
standard analogue cameras: Frame sensor concepts versus line 
scanning approaches, multi-head systems versus single head 
sensors, large image format data acquisition versus medium or 
even small format cameras, pan-chromatic and/or multi-spectral 
image data recording. All this results in different calibration 
approaches, which have to be defined individually for each 
sensor type. Additionally, due to the new parallel multi-spectral 
imaging capability (which is one of the major selling points for 
the new digital sensors), calibration should not only be 
restricted on the geometric aspects but has to be extended on the 
radiometric part also. The second fact is mainly due to the 
integration of the imaging sensors with additional sensors for 
direct sensor trajectory determination like GPS or integrated 
GPS/inertial modules. The combination of digital imaging 
sensors with direct orientation components is straightforward, 
since they provide very accurate information on the sensors 
movement, which can be used for fast generation 
photogrammetric products like ortho images. In case of line 
scanning systems a tight coupling with GPS/inertial sensors is 
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even mandatory to allow for an efficient image data processing. 
Hence, calibration has to cover the whole sensor system 
consisting of imaging part and additional components like 
GPS/inertial sensors. From this background the need of more 
complex, extended and more general calibration procedures is 
evident, where the aspect of in situ calibration will gain in 
importance, since calibration should cover the whole sensor 
system not only the optical part. 
This today’s situation defines the framework of the EuroSDR 
initiative on “Digital Camera Calibration”. Within this project a 
network is established formed by experts from different 
expertise. The following sections of this paper will present a 
short overview on the project goals, history and the ongoing 
work. In the second part the calibration approaches and process 
steps for three already operational digital airborne sensors are 
described, to illustrate differences and complexity of modern 
digital camera calibration. 
2. PROJECT “DIGITAL CAMERA CALIBRATION” 
2.1 Project history 
In summer 2003 the Steering Committee of EuroSDR has 
established a core network of some key researchers in the field 
of digital camera calibration to initiate a research project inside 
EuroSDR with the goal to derive the technical background for 
calibration procedures of digital cameras based on scientific 
theory and empirical investigations. Legal and organizational 
aspects for certification are put to the background for the time 
being. Within a very first initial meeting during 
Photogrammetric Week 2003 in Stuttgart/Germany all larger 
digital airborne camera producers already signalised their 
willingness to support this EuroSDR initiative. Based on this 
motivating kick-off the initiative was officially accepted and 
established during the 103" EuroSDR Science and Steering 
Committee Meetings from October 15-17, 2003 in 
Munich/Germany. At the time of writing the project is running 
in its first phase, where already 35 experts from research,