More recently, several studies have successfully demonstrated the use of SfM for generation of very high resolution 3D point clouds and surface models from UAV imagery. For example, a photogrammetric technique was used to derive a DSM and orthophoto for a landslide in southern France at a spatial resolution of 4 cm, and photogrammetric and SfM approaches have been used to generate sub-decimetre resolution DSMs from overlapping aerial photography acquired by a fixed-wing UAV for the purpose of soil erosion monitoring. SfM techniques have been used to generate accurate orthophoto mosaics from a multi-rotor UAV at 1 cm resolution with 10 cm absolute geometric accuracy, and the accuracy of the SfM derived point clouds was quantified for a coastal erosion study, which concluded that absolute accuracies between 25 and 40 mm can be reached with a multi-rotor UAV flying at 40 m above ground level (AGL). Eisenbeiss and Sauerbier (2011) reviewed a range of UAVs and 3D processing workflows for photogrammetric applications and Verhoeven (2011) described a software workflow based on Agisoft Photoscan for 3D reconstruction from aerial photographs in the context of an archaeological application. Finally, Rosnell and Honkavaara (2012) compared an online processing approach, Microsoft PhotoSynth, to a more rigorous photogrammetric approach using SOCET SET. These recent studies all indicate that accurate 3D point clouds and surface models can be derived from multi-view UAV imagery at ultra-high spatial resolutions of several centimetres (depending on flying height). With the recent introduction of commercial software packages, such as Agisoft Photoscan and Pix4UAV, and the increase in computing power (on both CPU and GPU) the SfM approach will become more readily available for UAV users.