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SOME RECENT NON CARTOGRAPHICAL APPLICATIONS OF PHOTOGRAMMETRY
AT THE INSTITUT GEOGRAPHIQUE NATIONAL
(Summary of the paper to be presented to Commission V)
Since the photogrammetric method makes it possible to determine the shape and
the dimensions of one object from a pair of photographic pictures, its use offers undoub-
tedly bya great interest for establishing a perfect similarity between an object of large di-
mensions and its small scale model, or studying the displacements or deformations of some
surfaces as a function of time. To the first group of applications, leaving aside cartogra-
phy, belong the reproduction of archaeological vestiges of deep interest, the control of
small scale models of turbine screws and the study of the shape of certain surfaces. In the
second group, appear rock dams deformation checking, the measurement of glaciers displa-
cements, the localisation of trajectories. Each of these non cartographic applications of
Photogrammetry having its own aspect and introducing a peculiar problem is studied sepa-
rately.
The photogrammetric method for rock dams deformation tests is based upon the
comparison between several plottings of the down stream slope faces, made from pictures
taken at time intervals varying accordingly to the age and strength of the dam.
If this method remains, presently, the only one to allow, with a sufficient accuracy
(a few millimeters) the measurement of the deformations, its cost is only justified if it
has been possible to detect previously anomalous distorsions ; for this previous detection,
a method is proposed which fulfils the three conditions : simplicity, rapidity of execution and
possibility of a qualitative representation of deformations.
When studying the evolution of glaciers, aerial photogrammetry offers the possibi-
lity of establishing with a given and constant accuracy plottings of glaciers, allowing to
reduce by a great proportion the necessary ground work or even to suppress them comple-
tely when sufficient ground control is available ; it makes apparent the caracteristical fea-
tures of the evolution of ice topography, necessary base of progress in glaciology.
The application of the photogrammetric procedure to architecture is not a new one.
Attention must be paid nevertheless, in this field of investigation , to the survey , by
terrestrial photogrammetric method, of some temples of High-Egypt. Those surveys were
undertaken on request of UNESCO, for the safeguarding of Nubian munuments.
Photogrammetric process enables without any difficulty, the plotting at the same
scale, of surfaces of similar shape. The accurate testing of this similarity is important
in hydraulical matters for power and efficiency studies of turbines, from small scale models.
As for radio-astronomy, it is necessary that the surfaces of wave reflectors coincide
with their theoretical shape (plane, sphere or paraboloid) within a given tolerance ; the pho-
togrammetric process makes it possible to check such surfaces of some hundred or even
some thousand square meters with errors not exceeding a few millimeters and to test also
that their motions do not introduce intolerable deformations.
The Photogrammetric process enables also accurate cubatures of volumes (for
example coal stores for thermal power stations).Pictures are taken at low altitude, from
an helicopter for instance, permitting the plotting at very large scales.
At last the photogrammetric procedure can be applied to the plotting of submarine
floor , using photographs taken below the water surface with cameras equipped with the
Ivanoff pre-lens, which corrects the aberrations arising from water and so enables plotting
in the usual way.
