**5. Discussion**

The MPT\_2.0 has proven to be a highly suitable instrument for georeferencing and documenting the impact of geophysical (landslides, avalanches) and hydrological (debris flows, floods) natural hazards. As reported in **Table 1**, the achieved theoretical precision for the presented study cases ranges from decimeters to a few meters, which is more than acceptable for practical purposes. In addition to the image quality and its resolution in particular, the precision of the system additionally depends on the DEM resolution and on the number, clarity, and distribution of the control points. The combination of highly resolved DEM and unambiguous (e.g., constructions), well-distributed CPs easily result in sub-metric precision.

Local significant deviations in the reconstructed position in monoplotting with respect to the real world may, in contrast, occur when there are objects in the background landscape of an image, or when areas in the landscape display a small incidence angle with respect to the camera ray. Here, small imprecisions in clicking on the corresponding image pixel may result in a great displacement of the corresponding real point where the ray intersects the DEM. In case of crests and ridges, the ray may even overshoot the DEM and hit the background landscape or get lost in the sky.

Additional sources of error are changes in the terrain morphology that took place between the time the image was shot and the DEM measurement. These may have originated in anthropogenic mass movements or by natural events such as landslides. In the latter case, only the untouched margins of the terrain changes may be localized with the monoplotting technique (see **Figure 4**).

Similar achievement potential and limitations of the MPT\_2.0 in terms of usefulness and achievable precision have been reported in independent scientific studies in the field of historical landscape reconstructions [36] and treeline ecotone dynamics [37].

According to our accumulated experience utilizing the MPT\_2.0, the required time investment highly depends on (a) the epoch of the event (the further back in time, the more the landscape may have changed, and the fewer available control points), (b) the quality of the image regarding the extent and form of the object to be digitalized (from local land slide to regional floods), and (c) on the available information (shooting location in particular). Thus far, most oblique images with suitable CPs were successfully processed with the MPT\_2.0 in a short time. The most time-consuming steps relate to the preparation of basic information such as the DEM, maps, orthophotos, images of the area in question, and the definition of the CPs (**Table 2**).
