Although in general terms the VDS returns very good results, the accuracy depends on several factors such as the spatial accuracy of the image from which the VDS was extracted from, the size of the vessel versus image resolution, vessel shape and material, quality of the acquisition and conditions of the sea surface (i.e. wind and waves). Vessel detection is performed using automatic algorithms and it is supervised by a human. Nonetheless misdetections (or non-detections) can still occur in this process, depending on the conditions mentioned above.