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.
