As Aplicações da fotogrametria aos estudos geomorfológicos

Resumo

After having recalled that the descriptive as well as the evolutive geomorphology lead to the establishment of maps, the author, Prof. Francis Ruellan, makes a distinction between the regular and detailed geomorphological map and the geomorphological map of recognition.

            It was during the work of the expedition he conducted in order to localize the sites of the new capital of Brazil, that the author defined his· ideas on the matter and, with the help of pictures taken with the trimetrogon, he established schemes for the groups charged with the setting up of itineraries.

            He then insists on what can be expected from the air pictures and what can be measured on them once apparatuses of great precision are employed. He first examines the different types of structure as they appear in the air picture; further, anything relative to the erosion caused by rain, wind and sea, summing up the problems of the descriptive geomorphology. He then refers to the evolutive geomorphology and shows how the study of the erosion surfaces, for instance, as well as all facts in connection with the dissection of the surfaces of erosion and accumulation, must be based on measures.

            Thus, it can be seen that everything is reduced to two fundamental problems 1) - one, of qualitative interpretation, which constitutes the proper geomorphology, applied to the study of air pictures;

2) - the other, of quantitative interpretation, which requires direct measures in the three dimensions, or indirect in the case of course or declivity. For the abstention of these measures which comprise a geomorphometric analysis of pictures and are, therefore, connected with the processes of the land and air photogrametry, it is necessary to employ with preference stereotopographs of great precision.

            The author ends this article pointing out the advantage of oblique pictures, such as those obtained through the helicopter, and then describes the series of operations which must be carried out in flight, at the laboratory and in the field, to return finally and finish the map at the laboratory.

            A geomorphological map organized in this manner will be not only of interest in a scientific way, but will also be of use to the agriculturist, as well as to the mining or the public works engineers, as they will be able to base their observations and interpretations on exact measures.