title: Measuring recent geomorphic changes using digital photogrammetry
title: An improvement in the measure of recent geomorphic changes using digital photogrammetry
titleType: AlternativeTitle
Creators: name: González-Díez, Alberto
name: Fernández Maroto, Gema
name: Cardenal, Javier
name: Mata de Castro, Emilio
name: Pérez García, José Luis
name: Delgado-García, Jorge
name: OTERO, CÉSAR
name: Bruschi, Viola María
name: Díaz de Terán, José Ramón
name: Remondo, Juan
Publisher: name: Zenodo
Year: 2025
Subjects: Digital photogrammetry
Landslides
Geomorphic changes
Spain

description: An improvement in the measure of recent geomorphic changes using digital photogrammetry Abstract Text Changes manifested in the relief are principally due to the dynamics of either externa! or intemal earth processes, climate change or human intervention. Extemal processes are in continuous change however its dynamics can be shown either as a slow and progressive geomorphic change or as significant relief modifications. Obviously, geomorphic change must be considered as modifications on slope geometry. Landslides are an excellent example of these geomorphic changes, because they represent an important contribution to denudation and relief evolution processes. lt is therefore of interest to know to what extent recent/present (a few decades) slope instability processes are contributing to geomorphic mass transfer, and also whether their activity show changes that could be assigned to variations in the landslide triggering factors (seismic, tectonism, climate and human). To measure the importance of the man as an agent modifier of the relief and to compare its role in the geomorphic change with others extemal processes as landslides, are two of the ideas that at present time appear like more attractive in earth sciences. Probably, aerial images are the source of information more used to analyse recent geomorphic changes. And this is because these have high metric and semantic possibilities to extract information about the landscapes depicted. In developed areas it is possible to use images from flights corresponding to different ages, sorne of them older than 1950th, to analyse the relief modifications. Obviously the modifications analysed correspond to the time span between new and old images. The present work shows different methodological approaches for the measuring of the geomorphic change using digital photogrammetric techniques. Digital photogrammetry allows: A good coverage with a reasonably high precision of the slope geometry; To use the technique with existing data and with data from the past (historical aerial images); To measure thousands of points in a short time, obtaining precise, high point density models. The examples found in the literature that shows the use of this technique, in addition to provide accuracy and precision digital elevation models, also contains sorne problems, as errors in the differences between the relative origins of each set of images. So the differentials measured in the absolute displacements are considered as real displacement registered between landslides from different ages. In order to correct this type of errors, a right measure of the real displacement must be done. Other problem detected, for instance, is to obtain mobility rates from volumetric measures. The improvement of these measures let us to obtain better precision in the absolute orientation of the flights, and therefore, an increase in the accuracy of the real geomorphic change. The data obtained for landslides compared with thus obtained for the human intervention in the slopes, also let us to know the role of the man in the landscape change. Symposium titles GSM-01 GSM-01 General contributions to geomorphology Presentation Preference Oral presentation