## 5 Conclusions  
In this study, the topic of cell size selection for landslide susceptibility mapping units was explored. In particular, the exploitation of a reliable three-type inventory allowed us to investigate potential reasons why differently sized models produce differences in terms of performance. On the basis of the obtained results, the optimal selection of the cell size has to be based on multiple modelling so as to analyse and explain differences and more objectively select the best size. As expected, the small but significant differences in the AUC performances corresponded to weak but coherent differences in terms of binarised predicted status. At the same time, if we can consider any of the model sizes as largely acceptable (at least for slides and slope flows), the 8 m best-performing model allows the user to correctly read the susceptible conditions, as given by the morphological setting. Landslide susceptibility model validation tests are typically focused on accuracy and precision assessment derived from cross-validation procedures. However, when using grid cells as mapping units, it is essential to verify the robustness of a model to the change in cell size for the evaluation of either the reliability or the geomorphological adequacy of the obtained results. For this reason, further efforts should be devoted to the topic, enlarging the fan of study areas and related geomorphological settings as well as the types and the relative size of the considered landslides. Nowadays, obtaining high-resolution DTMs is not as hard as in the past: the large use of Unmanned Aerial Vehicles (UAV) permits the acquisition of low-cost and user-friendly high-resolution DTM and orthophotographs. On the other hand, several nations are now covered by high-resolution DTMs, frequently obtained by satellite data or LIDAR sources, with free access for users. As regards the model-building procedures, these are also facilitated due to the high memory/capacity ofcomputers and the availability of free statistical software which permits the management of large amounts of data in a short time. Conceptualization, C.M., C.C. and E.R. ; methodology, C.M., C.C. and E.R. ; software, C.M. ; validation, C.M. ; formal analysis, C.M. and C.C. ; investigation, C.M. and C.C. ; resources, C.M. and C.C. ; data curation, C.M. ; writing--original draft preparation, C.M. ; writing--review and editing, C.M., C.C. and E.R. ; visualization, C.M. ; supervision, C.C. and E.R. ; project administration, E.R. All authors have read and agreed to the published version of the manuscript. This research received no external funding. Not applicable. The landslide inventory, digital terrain model, soil use and geologic layers adopted for this study can be requested from any of the authors. In addition, the DTM can be visualized and downloaded by exploiting the WCS server of the SITR webgis at the link (accessed on 8 January 2023): [[https://map.sitr.regione.sicilia.it/gis/services/modelli_digital/mdt_2013/ImageServer/WCSServer](https://map.sitr.regione.sicilia.it/gis/services/modelli_digital/mdt_2013/ImageServer/WCSServer)]([https://map.sitr.regione.sicilia.it/gis/services/modelli_digital/mdt_2013/ImageServer/WCSServer](https://map.sitr.regione.sicilia.it/gis/services/modelli_digital/mdt_2013/ImageServer/WCSServer)). The adopted soil use map is the one available from the Corine coverage; it can be downloaded at the link (accessed on 8 January 2023): [[https://land.copernicus.eu/pan-european/corine-land-cover/clc2018?tab=download](https://land.copernicus.eu/pan-european/corine-land-cover/clc2018?tab=download)]([https://land.copernicus.eu/pan-european/corine-land-cover/clc2018?tab=download](https://land.copernicus.eu/pan-european/corine-land-cover/clc2018?tab=download)). The research whose results are here presented and discussed was carried out in the framework of the SUFRA (SUscetbilita da FRAna) project, funded by the Basin Authority of the Hydrographic District of Sicily (Scient. Coord. [PERSON]).