XIII Congress of the
International Society for Photogrammetry
Helsinki, 1976
Commission V
Working Group V/3
Invited Paper
N. BALASUBRAMANIAN
Springfield, VA, 22152
Comparison of Optical
Contouring Methods
Optical contouring methods are still not competitive with
stereophotogrammetric methods.
INTRODUCTION
In IDEA OF generating contours of
constant elevation as a means of geomet-
rically measuring a close-range object has
fascinated many investigators, and over the
last few years this has resulted in numerous
optical contouring techniques. A large
number of these techniques are based on
theoretical propositions; however, many of
them have also been experimentally dem-
technique over the other under any given
situation. Most of the direct optical contour-
ing schemes are applicable to only small ob-
jects since all of them require artificial illu-
mination, coherent or incoherent, of the ob-
ject scene. Examples of such objects are
machined parts, human body organs, biologi-
cal specimens, etc.
The various types of optical contouring
methods that have been proposed and dem-
ABSTRACT: In the last few years several direct optical contouring
schemes have been proposed and demonstrated. An effort is made in
this paper to identify some of their characteristics and evaluate their
performance as it relates to their application in close-range photo-
grammetry. It is shown that, even though these systems exhibit poten-
tial and promise, further development in technique is necessary be-
fore they can become competitive to stereo-photogrammetric sys-
tems.
onstrated. Each of them claims to offer u-
nique advantages over similar methods. The
applicability and the advantages offered by
specific methods depend on the nature ofthe
measuring problem and hence it is very dif-
ficult to objectively compare these methods.
The intent of this paper is to evaluate and
identify the performance characteristics of
some of the direct optical contouring
techniques reported in the literature. It is
hoped that such a comparison will permit one
to derive qualitatively the advantages of one
PHOTOGRAMMETRIC ENGINEERING AND REMOTE SENSING,
Vol. 42, No. 1, January 1976, pp. 115-120.
onstrated are too many to be covered in this
paper. Hence only a selected number of the
contouring methods are considered in this
evaluation. The different methods consid-
ered are (1) Moiré contouring methods, (2)
contouring with holographic interferometry,
(3) contour generation with optical process-
ing of stereo photographs, and (4) contouring
from holographic images. The last of the
above methods is nota direct optical contour-
ing method; however, it is included in this
evaluation because it represents a novel solu-
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