scored in the lefc socket during this last 
test, and the stereoplotter operator was 
able to see them quite clearly in the 
model. The rough contour lines indicate the 
operator's recognition of those groove 
marks. More frequent contour intervals 
could have been plotted, which would have 
defined the grooves more precisely, but for 
purposes of comparision, it was decided to 
stay with the same format that had been 
used for measuring the previous stages. In 
Figure 8, note that the low point of the 
right socket on the final manuscript shows 
only a slight amount of wear when compared 
to the original low point in the right 
Socket. However, the low point in the left 
Socket shows a change from 0.910mm to 
0.803mm, indicating wear in the amount of 
0.107mm (0.004"). 
In each case, the researchers at MIT 
measured the wear on the concave sockets 
using their original X-Y-Z micrometer 
block system. Because of the difficul- 
ties with this original system, they came 
to the conclusion that the photogrammetric 
method was indeed more accurate, since the 
results appeared far more reasonable than 
those from the original measuring system. 
Because of the 7X magnification used in the 
photogrammetric approach, the stereoplotter 
operator could easily read the stereo model 
within a real world tolerance of +.005mm. 
However, even the best of metric lenses for 
cameras and stereoplotters contain a certain 
amount of distortion. Therefore, for each 
test, the polyethylene tibial component was 
photographed in the same physical location 
in respect to the camera lenses. And the 
thickness of the opaque coating was also 
the same in each instance. Therefore, the 
relative wear that was discovered during 
each stage of measurement was valid. 
  
The experiment proved that the photogram- 
metric approach for measuring the wear on 
a polyethylene tibial component was not 
only cost effective — it was indeed more 
accurate as well. 
III. CONCLUSION 
The potential for close-range photogram- 
metry is enormous. For example, the Kelsh 
K-470 Terrestrial Camera has been used for 
the analytical measurement of fabrication 
fixtures in an air frame assembly plant. 
It has also been used to measure clay 
models of future automotive designs for 
the preparation of stamping dies. 
We have talked about the potential appli- 
cations for close-range photogrammetry for 
many years, in and out of the photogram- 
metric profession. The universities have 
demonstrated the workability and accuracy 
of the close-range technique in a variety 
of experiments. Many manufacturers such 
as ourselves have been encouraged to 
design and build cameras and plotters for 
those applications. 
The publicity that close-range has been 
enjoying is creating a growing market out- 
side of the mapping profession. There are 
many diversified industries that need our 
form of measurement now, and are requesting 
our help in implementing it! There is no 
doubt that the practicing photogrammetrist 
has an immediate opportunity to broaden his 
market and to build his business in this new 
and exciting field. 
References: 
l. Danko, J. 0..,Jr. and Cuzzi, J. R., "The 
Kelsh K-460 Stereometric Camera — A New 
Tool for Close-Range Applications", 
Paper No. 76-216 in the 1976 PROCEEDINGS 
of the Annual Meeting of the American 
Society of Photogrammetry. 
2. Ross, R. M., Radin, E. L., and Paul, T. 
L., "Repairing the Human Skeleton: 
Materials for Orthopaedics", published 
in TECHNOLOGY REVIEW, Vol. 76, No. 5, 
March-April 1974, pp. 32-41, a publica- 
tion of the Massachusetts Institute of 
Technology.