Image - based mapping of surface fissures for the investigation of landslide 1 dynamics 2 3

13 The development of surface fissures is an important indicator for understanding and forecasting slope 14 movements. Landslide investigations therefore frequently include the elaboration and interpretation of 15 maps representing their spatial distribution, typically comprising intensive field work and 16 instrumentation. Only recently aerial photography with sub-decimetre spatial resolution is becoming more 17 commonly available and opens a window to analyse such features from a remote sensing perspective. 18 While these data are in principle helpful to elaborate maps from image interpretation techniques, there is 19 still no image processing technique available to extract efficiently these geomorphological features. This 20 work proposes a largely automated technique for the mapping of landslide surface fissures from very-high 21 resolution aerial images. The processing chain includes the use of filtering algorithms and post-processing 22 of the filtered images using object-oriented analysis. The accuracy of the resulting maps is assessed by 23 comparisons with several expert maps in terms of affected area, fissure density and fissure orientation. 24 Under homogenous illumination conditions, true positive rates up to 65% and false positive rates 25 generally below 10% are achieved. The resulting fissure maps provide sufficient detail to infer 26 mechanical processes at the slope scale and to prioritize areas for more detailed ground investigations or 27 monitoring.