Stefan Diener 
  
RADIOMETRIC NORMALISATION AND COLOUR COMPOSITE GENERATION OF THE DMC 
Stefan Diener, Michael Kiefner, Christoph Dörstel 
Z/I Imgaing GmbH, PO BOX 11 06, D-73442 Oberkochen, Germany 
{Diener, Kiefner, Doerstel} @ziimaging.de 
Working Group I/2 
KEY WORDS: Algorithms, Image processing, CCD, Multi-spectral data, Radiometric quality. 
ABSTRACT 
This paper describes the aspects of data processing from the raw image to the colour composite of the Digital Modular 
Camera (DMC) of Z/I Imaging. Since photogrammetric applications demand high precision inside the images, a 
radiometric normalisation has to be done with the raw image data. 
To normalise CCD line-arrays look up tables are stored during the calibration procedure. Looking at CCD matrix-arrays 
with high resolution and to a principle used in DMC with a couple of CCD matrix-arrays, the necessary storage for look 
up tables increases dramatically. 
Therefore one has to determine functional coherence between the radiometric behaviour of the CCD and the influencing 
factors. This paper describes which influences are expected and how to store the resulting parameters and look up tables 
(LUT). 
The images taken by the 4 panchromatic cameras have to be transformed into a single mosaiced image. This mosaic 
covers the same area on the ground as the multi-spectral cameras do, but the resolution is four times higher. 
Our aim was to generate a colour image with the geometrical accuracy of the mosaic image, i.e. a colour composite. 
Therefore we fused the colour information of the 3 multi-spectral images with the luminance data of the mosaic. The 
main task is to separate the luminance from the colour information so that it is possible to replace it. This paper 
describes the used workflow, the investigations about several colour space transformations and their results to select the 
best practice. 
1 INTRODUCTION 
The Digital Modular Camera (DMC) is the new digital aerial camera system of Z/I Imaging. With this system the last 
lack of the digital chain in aerial photogrammetry is closed. The key issue of the whole photogrammetric workflow is 
the geometric image accuracy, which is mostly defined by the camera sensor itself. In order to fulfil the high 
requirements of mapping applications, Z/I Imaging has decided to base the new DMC on a CCD-matrix sensor, because 
of its stable geometry. 
According to its modular design, more than one individual camera module can be tied together, resulting in a large field 
of view of the camera. The full equipped configuration of the DMC is composed of four panchromatic modules and up 
to four multi-spectral channels. The four panchromatic modules have their optical axes looking downwards in a slightly 
divergent set up to reach a large ground coverage. A post-processing procedure (“mosaicing”) serves to transform the 
four individual images into one virtual image which can be considered as normal central projection. The multi-spectral 
modules are arranged along the flight direction and acquire nadir looking views. The colour imagery has the same 
ground coverage as the panchromatic one but only the sixteenth part of the number of pixels [Hinz2000]. This leads to a 
footprint as shown in figure 1. 
  
82 International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B1. Amsterdam 2000. 
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