Confirmation of ditched enclosures aerial images has several stages. After identification on an image, it is important to go to the place and see if there is prehistoric material on the surface. If so, the finding is reinforced, but some still need deeper confirmation and definition, that can be obtain by geophysical survey or traditional excavation survey. At this stage of our project we are just performing the two first steps (occasionally, as in Monte das Cabeceiras 2, mitigation work allowed confirmation through diggings).
Nevertheless, in the first step (identification by aerial image) there is a way of controlling the quality of the information: if the same signs appear in images from different years, especially if they have several years of interval, than the probability of a correct identification increases significantly, as it happens in this new case, in Portalegre district. We still don't have surface confirmation for this one, but it looks like a double ditched enclosure (like the outside ditches of Perdigões, or Monte das Cabeceiras or Salvada, but not with the internal sinuous ditch of the later two). It will havemore than 200m of maximum extent, which will put it in the middle size group of enclosures. The left image is from 1995 and the right one is from 2006. Eleven years in between clearly reinforce the interpretation.