²⁶O’Driscoll, James. “A Case Study for Landscape Applications of Drone and Photogrammetry Techniques: Faha and Caherconree Hilforts, Co. Kerry.”
Journal of the Kerry Archaeological and Historical Society, Series 2 2018. V. 18. p. 47.

The author writes in a different article, "Viewshed analysis is a technique that aims to 'identify those areas that can or cannot be seen from a single (or a set of) viewpoint(s) within a digital model of a terrain, either by calculating line-of-sights between pairs of point locations or via viewshed generation' (Paliou 2013: 2). Wheatley and Gillings (2000: 1) suggest that viewshed analysis is the most unique and valuable GIS application for archaeologists." 9O’Driscoll, James. “Picture Perfect: Using Drone Technology and Photogrammetry Techniques to Map the Western Stone Forts of Ireland.”
Journal of Field Archaeology, 44:2, 126-146. p. 128.)