THE PERFORMANCE OF THE NEW WIDE ANGLE AIRBORNE CAMERA (WAAC) 
Andreas Eckardt 
DLR- Institute for Space Sensor Technology 
Rudower Chaussee 5.D-12489 Berlin Germany 
Tel.: (xx4930) 69545539 
Fax.: (xx4930) 69545532 
e-mail: eckardt@sunnyboy.ws.ba.dir.de 
ABSTRACT: 
The WAAC- camera is a new 3 CCD- line scanner development based on the Wide Angle Optoelectronic Stereo Scanner 
(WAOSS) and shall be presented the first time to a wide community. The scientific and technical concept of the camera will be 
introduced and compared with the WAOSS- camera. 1 
Characteristics and technical performance data of the WAAC- camera are given. The new camera derived from WAOSS has to 
fulfil the demands of airborne use. The WAAC camera is characterised by a low mass and power consumption (15W, 4kg) and 
will be controlled by a Laptop PC rather than rack mounted high volume controller. This Laptop has to managed the high 
speed data rate coming from the WAAC data channels. They allow the on- line data storage and visualisation. The first test 
flight will be in the April of 1995. 
It is an experimental camera to study the behaviour of CCD- push broom scanners with respect to their photogrammetric use. 
The camera is prepared for an automatical on- line control of the imaging process. 
1. INTRODUCTION 
The WAAC- camera represents a new generation of the Wide Angle Optoelectronic Stereo Scanner (WAOSS) which is a design 
for the Mars mission in 1996 (2). The WAOSS- camera was developed to fulfil the demands of science and spacecraft 
requirements of the mission. The main technical restriction on the camera was the low speed datalink to the spacecraft 
memory. The WAOSS- camera has to meet also the usual requirements for space applications. These requirements are 
hardware redundancy, low mass, and low power consumption. 
The WAAC- camera is a development for airborne applications. This camera has not any restrictions due to space qualification 
requirements. The new camera electronic design can be used for on- line control of the image process. For the on- line data 
processing it is necessary to use new circuits and hardware architectures. The results of the new design are the more flexible 
applications and the possibility of external and internal triggering. 
2. REQUIREMENTS ON THE WAAC CAMERA 
The requirements on the WAAC- camera can be splited in two main parts. The first part contain all scientific aspects and the 
second part contain all technical aspects. 
At first it is necessary to describe the science background and the reason for the WAAC- camera design. The reason for this 
step in the camera development was the experience of airborne experiments with the WAOSS- camera (2) (4). For the 3D 
reconstruction of the 3 CCD- line images it is necessary to find a great number of match points in the images. The image 
processing of decompressed macro pixels is the standard scientific mode of the WAOSS- camera. For this image calculation it 
is necessary to know all influences of macro pixel building and compression. 
So it was necessary to examine the WAOSS- camera control by a test facility which has no restriction caused by the special 
MIL- interface datalink. The test images were taken from opencast minings in Germany. The advantage of these test regions is 
the availability of 3D digital reference models with a resolution of 15cm. The WAAC- camera has the task to generate high 
resolution image data with full resolution for examination of the image processing algorithms. 
The pitch, yaw, and roll movements of the aircraft are measured by gyros. The global information of the camera position are 
received from the aircraft navigation system (GPS). All the information is stored in HKD- files. The synchronisation is realized 
by the line trigger output signal from the WAAC- camera. 
One scientific requirement on the WAAC- «camera consists in the calculation of 8 Bit 3D images. The camera has a resolution 
over ground of 1,60m at an altitude of 5km. The scientific requirement of 8 Bit radiometric resolution initiate the introduction 
of the analog correction of the Photo Response Non Uniformity and the Dark Signal Non Uniformity of the sensor (2). The 
WAAC- camera has the possibility to generate 11 Bit raw data, 8 Bit normalised data. and JPEG data. The generated data are 
compared with the decompressed data and the results are used as input values for the estimation of characteristics for data 
compression and compression control. 
3. CONCEPT AND STRUCTURE OF THE CAMERA 
Figure 1. shows the WAAC- camera structure and the open camera concept WAAC has the possibility to change the camera 
head, to use other sensors, to work with other processors or special processors, and interfaces. The standard interface of the 
concept is the wide SCSI Il interface (1). 
IAPRS, Vol.30, Part 5W1, ISPRS Intercommission Workshop "From Pixels to Sequences " Zurich, March 22-24 1995