Summarising, the accuracy achieved using 35 mm non-metric photography and
an unsophisticated co-ordinate measuring device, proves that the method is simple,
cost effective and efficient. Therefore it is perfectly commendable for the
applications and purposes that were presented earlier on.
5. Considerations for the photogrammetric evaluation of 35 mm negatives
Analogue plotting from the 35 mm kite photography was also attempted. Enlarged
diapositives were produced for the accommodation of the principal distance on the
Officine Galileo Stereosimplex IIB. Unfortunately relative orientation was not
possible, firstly, because of the small size of the diapositives and, secondly,
because of the large omega and phi rotations (Table 4). Consequently, the use of
& universal instrument, like the Wild A5, was considered. This would require
further enlargement of the negatives, thus deteriorating substantially the photo-
graphic definition. Moreover, the use of an expensive plotter would defeat the
argument of cost effectiveness and simplicity of the whole procedure. As a result
of these considerations analogue plotting from 35 mm negatives has been abandoned
for the purposes of this exercise. It is believed, however, that there is some
useful potential in 35 mm non-metric photography. The nature and coverage of kite
photography strongly suggest that multistation adjustment (Granshaw, 1980) could
provide & rigid and rigorous solution. The application of this method using 35 mm
negatives needs further investigation.
6. Critical evaluation of the system
In the following the limitations and possible improvements for the kite
photography system will be assessed. The whole procedure will be examined, from
obtaining the photography to producing the final results.
The kite is a mechanism very much dependent on the wind. In the case of kite
photography fairly strong and especially steady winds are necessary. The direct
relationship between wind speed and payload is shown in Table 2. Thus the main
limitation on the applicability of the kite photography system is again the weather.
Practical experience has shown that a steady breeze of 5 knots is a minimum re-
quirement. Moreover, a suitable lau-nching site is also required and should be
situated away from trees, high buildings or any other feature that would cause
turbulent wind droughts. However, for 80% of the time in the Greater London area,
consistently throughout the year, the wind speeds are favourable for kite photo-
graphy. Of course, rainy periods should be taken into account, but they normally
do not exceed LO% of the time in the Greater London area (Anon., 1976). This is
another limitation to the kite system, as rain water upsets the porosity of the
fabric on the Dunford kites and they lose their stability.
Furthermore, three or four persons is the minimum required manpower for
completing a project. Some way of communication should exist, especially in this
case, where the navigator may be obliged to stand quite far away from the actual
site. Another problem is the difficulty of exactly positioning the camera above
a certain target. The use of a 35 mm non-metric camera with a cloth focal plane
shutter combined with the camera platform movement, could cause unpredictable
image distortion. This is avoided by the use of fast shutter speeds and by taking
each exposure when the kite is hovering. Finally, the difficulty of orientation
of the camera is another limitation, which becomes unimportant when analytical
methods for processing the data are employed.
The photogrammetric procedure that was suggested and tested proved to be
simple, cost effective and within acceptable accuracy limits. Access to an
electronic computer or a mini-computer is, of course, a presupposition. Summarising,
the kite photography system is an efficient, simple, easily transportable and cost
effective means of obtaining photographs from low altitudes. It is, however,
sensitive in weak and variable winds or within confined areas.
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