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STATE-OF-THE-ART OF CLOSE-RANGE PHOTOGRAMMETRY 77 
These new types of graphics are very illustra- 
tive and can increase the interest for photo- 
grammetry. The possibility of choosing the 
orientation of sections, profiles, and contours 
is for engineering and industrial purposes 
also a means of widening the use of photo- 
grammetry. 
NUMERICAL RESULTS 
Although, in practice, the majority of cases 
make use of the analogue approach with 
graphical output, research and development 
efforts are devoted primarily to the analytical 
reduction of measured image coordinates, if 
one is to judge from the literature in the field. 
The availability of computers and the desire 
to use non-metric cameras even for accurate 
measurements have increased the develop- 
ment of analytical methods. The use of the 
photogrammetric data for further calcula- 
tions, data analysis, data banks, etc., has also 
promoted analytical methods. Further de- 
velopment in the future towards greater in- 
tegration between the photogrammetric data 
acquisiton and reduction phases on the one 
hand, and the succeeding data analysis on the 
other is to be expected. In order to reach this, 
close co-operation between photogramme- 
trists and consumers is needed. The classical 
photogrammetric methods (analoque or ana- 
lytical) are not always applicable and require- 
ments of potential new consumers are chal- 
lenges to all photogrammetrists. We must, 
however, not be too ambitious and measure 
everything photogrammetrically. There are 
other methods and the merits of different ap- 
proaches have to be judged so as to optimize 
the entire process of which the measurement 
often is just a minor component. 
The analytical approach can, as mentioned 
above, be used in the rather simple case 
where interior and exterior orientation are 
known, but its advantages and versatility be- 
come much more pronounced in the most 
general case of photogrammetry in which a 
simultaneous solution incorporates the inte- 
rior and exterior orientation elements of all 
photographs and the space co-ordinates of ob- 
ject points, all as unknowns. 
The nature of measurements is point-by- 
point where mono- or stereocomparators are 
used. Depending on the final output re- 
quirement this can be more or less conven- 
ient. It can happen that the photogrammetric 
phase of the job is best solved by analytical 
methods but the required result is best 
presented in continuous form. In such a case 
the techniques of digital modelling, surface 
smoothing, prediction and filtering can be ap- 
lied. This has been discussed in relation to 
non-topographical photogrammetry by Wong 
34 and applications are demonstrated for sev- 
eral biomedical cases by others?!. 16.17, 
By its nature photogrammetry is a versatile 
and convenient tool for studying objects in 
motion. There are several industrial and civil 
engineering examples, most of which belong 
to the analytical group. Both mono and stereo 
methods can be applied for objects moving 
in one, two or three dimensions. The move- 
ments can be very slow, e.g., structural de- 
formations$-32, They can be rapid, e.g., vehi- 
cle studies33, or they may be termed high- 
speed, e.g., ballistics, aerodynamics, bubble 
chambers. 
More uncommon projections are found in 
electron microscopy in that the principal dis- 
tances are very long, infinite, or even nega- 
tive. Photogrammetry can still be applied but 
of course not in the traditonal way. Kratky has 
given mathematical solutions.22.23 
The accuracy of different close-range 
photogrammetric procedures is often deter- 
mined by experiment and check measure- 
ments. For a large number of more-or-less 
standardized methods this has given us expe- 
rience and simple rules-of-thumb for judging 
the accuracy in a specific case. For other 
methods, more sophisticated means are 
applied to determine the accuracy of the re- 
sults. In some methods a rigorous adjustment 
of unknowns also includes the calculation of 
standard errors. In other cases, well-surveyed 
test fields are used, as in the experiments 
performed by Hottier!!-12, For a single 
stereomodel and analytical data reduction 
he has found a considerable decrease of in- 
accuracy 
e when the number of replicated settings 
on the same target is three instead of one 
(16 per cent decrease), 
® when the number of targets defining each 
point is three instead of one (30 per cent 
decrease), and 
e when the number of frames on each sta- 
tion is three instead of one (38 per cent 
decrease). 
Further, Hottier discusses the optimum 
combination of settings, targets and frames as 
well as the base-height ratio. 
CONCLUSIONS 
Photogrammetry has been used for a great 
many different non-topographical applica- 
tions. The range of images goes from electron 
microscopes to space cameras. Applications 
are found in the most diversified disciplines. 
The development of metric camera systems 
and evaluation equipment, as well as the in- 
creased use of analytical data reduction and