Fryer, John 
processes involved. These processes, such as demonstrable ray tracing in object space, provide strong visual evidence 
to a court in a manner comprehensible to a lay-person on a jury. 
2 HEIGHT DETERMINATION - TRADITIONAL PHOTOGRAMMETRY 
A scene captured from a video surveillance camera is shown as Figure 1. Surveillance cameras typically record at 
about two frames per second, so if a “normal” bank robbery is of 40 - 60 seconds duration, approximately 80 to 120 
images will be available for forensic investigation. 
It is most probable that in at least a few of these frames, the robber/s 
will be reasonably upright and standing in front of some permanent 
fixtures which can be used in the height determination process. For 
example, a consideration of Figure 1 shows a robber waiting for some 
money in front of the teller's grille, with the top of his head coincident 
with that grille and the location of his feet in identifiable positions on a 
patterned carpet. 
Most bank robbers are aware of the video surveillance cameras and 
wear masks or balaclavas to conceal their facial identification. The 
height of the bank robber cannot be so easily concealed and this is one 
piece of physical evidence which photogrammetrists can be called 
upon to provide to the court. 
The traditional photogrammetric method for obtaining the height of an 
object in a single image involves: 
e obtaining the original video tape or at least a good copy. This 
should always be attempted, but it may not be possible as some 
well-meaning policeman or lawyer may have had prints produced 
from the tape and it will be “lost”. These prints may be cropped in 
an unknown manner, adding to the skills required of the 
photogrammetrist. 
  
Figure 1. Bank robber. 
Note patterned carpet and top of head aligned 
with light ray to top of teller's grille. 
e a physical survey of the position of the surveillance camera in 
relation to some fixtures seen in the image. Usually tape and 
plumb-bob will suffice for the survey which sets up a local 
coordinate system. 
e adetermination of lens distortion and other camera parameters such as principal distance and offsets of the principal 
point. The radial lens distortion may be quite severe as usually a wide angled lens (short focal length) is chosen in 
order to provide for a wide field of view. 
e a space resection to find the orientation and location of the perspective centre of the surveillance camera. 
e the image measurement of the robber and then the solution to the problem as outlined in Figure 2, noting that the 
image coordinates of the head and feet must be corrected for offsets of the principal point and lens distortion. 
3 TIME DELAYS 
An unfortunate fact of life is that the photogrammetrist is usually summoned to provide forensic evidence only well 
after the incident occurs. Two or more years later is probably commonplace. If the thieves had been caught quickly by 
the police, there would be no need for the photogrammetrist as items of clothing, masks, guns or other physical 
evidence would still be present and the proceeds from the robbery would have been recovered. As Thompson (1962, 
432) once indicated, photogrammetry is often used only as a last resort, after simpler methods have not proved possible. 
The interior decor of banks often changes, much to the angst to the forensic photogrammetrist. Carpet wears out 
quickly in areas of high pedestrian traffic in front of the tellers’ area. After a robbery, it is not unusual to see the 
installation of security screens, new glass panels, etc. which destroy the background scene as it was at the time of the 
  
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B5. Amsterdam 2000. 247