A DIGITAL EXTENSION OF 
THE AUTOMOBILE COLLISION INVESTIGATION 
PHOTOGRAMMETRIC SYSTEM 
Wolfgang Faig 
Department of Surveying Engineering 
University of New Brunswick 
Fredericton, N.B., Canada 
Tian- Yuan Shih 
Department of Civil Engineering 
National Chiao-Tung University 
Taiwan, R.O.C. 
ABSTRACT 
A softcopy version of an economic photogrammetric system has been designed. This photogrammetric system 
was developed for automobile collision investigations. 
In the original film based system, the stereo-cameras 
constructed with two non-metric cameras are used to collect the photographic imagery. The photo coordinates are 
digitized with a slide-projector and tablet-digitizer combination. In the designed digital system, stereo-cameras are still 
used for image gathering. After the films are developed, the "soft" copy of the imageries are gathered with desktop 
scanners. With digital imagery, several schemes of different automation levels can be developed. This softcopy 
photogrammetric system eliminates the requirement of slide-projector and tablet digitizer. The stability and lighting 
condition for the working environment also become less critical. 
INTRODUCTION 
A photogrammetric system based on the non- 
metric stereo-camera approach (Faig & Shih, 1990) has 
been constructed for the car collision investigation. This 
system follows the analysis model described in Tumbas & 
Smith (1988). The only difference is that, instead of tape 
measurements, the deformations are measured by 
photogrammetric means. After the evaluation with data 
sets from real collision cases, this system has been found 
to be practical and useful (Faig, Wilson, & Shih, 1992). 
Currently, this system is used by several selected Multi- 
Disciplinary Accident Investigation teams (MDAI Teams) 
across Canada. 
After the completion of this photogrammetric 
system, further research has been conducted to 
investigate its improvements and the extension. After 
discussion and idea exchange with transportation 
professionals, a digital extension is found to be of general 
interest. This paper describes the design and 
implementation of this extension. The analogue system 
  
is described first, followed by the digital version. Then, 
the scanning process is discussed. Regarding to feature 
extraction, there are two directions of development as 
well. Both the manual approach and the semi-automated 
approach are discussed. 
THE ANALOGUE SYSTEM 
In the original photogrammetric system, a non- 
metric stereo-camera is used for data acquisition. This 
stereo-camera is composed of two fixed-focus compact 
cameras, a base-bar, a photographic tripod, and two 
camera mounts (Figure 1, 2). A slide projector and a 
tablet digitizer were utilized for the photogrammetric 
measurements. The digitizer is directly linked with a 
micro-computer, and all following computations are 
performed on this micro-computer as well. 
Within the camera, a set of four reference marks 
was established by gluing a brass frame onto the lens 
cone. In the four corners of this brass frame, tiny 
circular holes are drilled. With these reference marks, 
interior orientation can be calibrated in the system 
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Back of the 
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Figure 1: The Stereo-Camera 
  
  
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Figure 2: The Base Bar