Improvement of positional accuracy of a landslide database using digital photogrammetry techniques
Tomás Fernández 1, Jorge Delgado 1, Javier Cardenal 1, Clemente Irigaray 2, Rachid El Hamdouni 2 and José Chacón 2
1 Departamento de Ingeniería Cartográfica, Geodésica y Fotogrametría. Universidad de Jaén.
Campus de las Lagunillas s/n, Edificio de Ingeniería y Tecnología. 23071 Jaén, Spain
Tel.: + 0034 53 212 843; + 0034 53 212 454; 0034 53 212 844; Fax: + 0034 53 212 855
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2 Departamento de Ingeniería Civil. Universidad de Granada.
Campus de Fuentenueva, s/n, Edificio Politécnico. 18071 Granada, Spain
Tel.: + 0034 58 212 498; + 0034 58 212 496; + 0034 58 212 499; Fax: + 0034 58 212 499
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In this work several techniques for the elaboration of landslides databases are compared. The used techniques are the digitalization on ortophotographies (monoplotting), the digitalization on aerial photographs and geometrical correction, the translate to a topographical map and digitalization, and, finally, the stereoplotting using digital photogrammetry. The landslide scarps databases derived from the different methodologies have been compared by several indexes such as the displacement between significant points of scarps, the lengths of scarps, and the fitness of scarps to a DTM. The analysis shows some important discrepancies between the databases, with displacements between 18 and 40 meters, depending on the compared methodologies. The general best results are obtained with the methodology of digital stereoplotting whose scarps database is well fitted to the DTM. Among the rest of methodologies, the digitalization on ortophotography presents the lower differences with the previous one, followed by the digitalization on the map; in both cases the displacements and other changes do not show a pattern, which induces to think in errors of interpretation and digitalization. The methodology of the digitalization on photogram presents the worst results, although with a certain spatial pattern related with the relief displacement. The conclusion is to recommend the use of the digital stereoplotting to elaborate landslides databases and as possible alternatives the digitalization on ortophotography and on topographical map, being dissuaded the digitalization on the photogram, at least in zones with a strong relief.
Keywords: spatial accuracy, landslides database, digital photogrammetry
In: Caetano, M. and Painho, M. (eds). Proceedings of the 7th International Symposium on Spatial Accuracy Assessment in Natural Resources and Environmental Sciences, 5 – 7 July 2006, Lisboa, Instituto Geográfico Português