International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part BS. Istanbul 2004
global object coordinate system (object reconstruction). This
system is usually the same as the one in which the control
points are defined.
In the project described in this paper we were dealing with
non-metric images. We did not even know the camera type. No
control points were measured and very limited information was
given for scaling the image block. Also the texture information
in the overlapping areas was not sufficient to measure an
adequate amount of tie points. And finally, there was no
information available about the position from which the
pictures had been taken.
Thus the usual workflow of traffic accident evaluation could not
be directly applied and was therefore modified (Figure 1).
Scannon- , Approdmabonsf.
metric Photos Ext. Orientation |
Import Images & First Block
Create Pyramids . Adjustment
Estimate Interior Adjustment T
; ; Measure Tie and
Orientation Refinement Control Features
Y Data Snooping :
Measure fi
À True Block Introduce Fictitious
Tie-Points- Rescaling Observations
Datum Definition | | | Final Hybrid
(Arbitrary Scaling) - Adjustment
Figure 1: Project Flow
*
2. PROJECT DEFINITION
Four non-metric images depicting a motorcycle with a deformed
front wheel fork were given (Figure 2a and Figure 2b). No
control information (control points or orientation
approximations of the camera positions) were available and
there was no data available regarding the camera with which the
images had been taken.
o du A
igure 2a: n-metric image (a
Figure 2a: No t ge (a)
Figure 2b: Non-metric image (b)
The depicted motorcycle was involved in an accident. It had
crashed frontally into a car's side. The assessor needed to know
with what speed the motorcycle had been driving in the moment
of the collision. The only clues to derive such information were:
e angle a (see Figure 3) of a sharp bend that arose in
the upper right front fork during the accident.
e exact range between the front and rear wheel axes of
the deformed motorcycle!
If this angle and/or range could be precisely computed, a
technical specialist would be in position to derive the force
needed to emerge such a break and thus calculate the unknown
driving speed.
63l
Figure 3: Bent off wheel fork
Due to the complexity of the project and the limited information
that was provided, a program with a very versatile mathematical
background was needed, hence common off-the-shelf software
products for close range photogrammetry did not seem suitable.
The employed package should be able to handle hybrid
adjustment techniques (including fictitious observation
implementation). So, the project was carried out by using the
program system ORPHEUS (Kager et al. 2002), which is based
on the photogrammetric adjustment system ORIENT (Kager
1993).