2004 
  
INTRODUCTION OF THE 3-DAS-1 DIGITAL AERIAL SCANNER 
H. Wehrli* V. Gayda, G. Wehrli* J. Bethel*” 
*Wehrli & Associates, 7 Upland Drive, Valhalla, New York, 10595, USA, hiwehrli@aol.com 
b Geosystem, 600-Letiya 25, 21027, Vinnitsa, Ukraine, valery@vingeo.com 
* School of Civil Engineering, Purdue University, 550 Stadium Mall Drive, West Lafayette, IN 47907-2051, USA, 
bethel(ecn.purdue.edu 
Commission I, WG 1/4 
KEY WORDS: Scanner, Aerial, Camera, CCD, Linear Array, Pushbroom 
ABSTRACT: 
This paper describes the capabilities and preliminary results from a new digital photogrammetric scanner, the 3-DAS-1, which is a 
joint development between Wehrli & Associates and Geosystem. The system consists of the camera, a new stabilized platform, 
modules for power, control, and data collection, and software for diagnostic evaluation, system operation, and photogrammetric 
image processiong. The system is based on the three line scanner approach, and is designed to address the photogrammetric needs of 
the civil mapping community. First aerial imagery is, at the time of writing, just about to be collected. Laboratory imagery and 
evaluationsare presented in the paper. 
1. INTRODUCTION 
Based on work done collaboratively between Wehrli & 
Associates and Geosystem during the last decade to develop 
and manufacture a series of photogrammetric film scanners, it 
was decided in 2001 to continue this collaboration with the 
development of a digital airborne scanner for the direct 
acquisition of digital photogrammetric imagery. The 3-DAS-1 
is based on the well known three line scanner principle, hence 
the acronym. 1t is designed to address the civil mapping 
market. Wherever possible, all components of the system have 
been selected to modular, COTS (commercial off the shelf), 
and upwardly mobile. A pre-production model of the system 
has been completed, see Figures 1 and 2, and laboratory 
evaluationshave been carried out. At the time of writing, first : 
airborne data is about to be collected. Figure 2. 3-DAS -1 
  
2. SYSTEM DESCRIPTION 
The three sensors are part of the Kodak family of KLI trilinear 
(RGB) CCD arrays. This family of sensors is available with 
6000x3 12 micrometer pixels, 8000x3 9 micrometer pixels, and 
14400x3 5 micrometer pixels. Mechanically and electronically, 
the three types are interchangeable. Early computations 
indicated that, at typical line rates for fixed wing aircraft, the 
8000x3 array would accumulate sufficient charge to support 
high quality intensity quantization. The higher pixel count 
array might be suitable for slower line rates associated with 
helicopter platforms, and provide a migration path for higher 
spatial resolution. 
  
Figure 1. 3-DAS-1 Rather than attempting the use of a single, exotic objective lens 
to cover the entire field of view over the forward, nadir, and 
backward looking arrays, a separate object ive lens is used for 
each array. We have selected the well known family of 
Rodenstock Sironar HR objectives. This family of lenses is of 
recent design, especially created for use with digital sensors. 
The lenses are available in focal lengths of 35mm, 60 mm, and 
100mm. The 100mm lens has been selected for the current 
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