A Fresh View on the Nasca Lines: Investigating Geoglyph Visibility in Palpa (Ica, Peru)

The Nasca geoglyphs in southern Peru are today usually viewed from the air. This has led to the false impression that they are only visible from above. In contrast, archaeological evidence shows that a continuous and manifold chain of activities took place on geoglyph sites during the Nasca period (200 BC – AD 650), involving large parts of the ancient population. These activities likely required good visibility from the valley and from other geoglyph sites. The Palpa data set, comprising photogrammetrically recorded geoglyphs and a digital terrain model (DTM), allowed for the first time a geographic information system (GIS)-based study of geoglyph visibility, which is described in this paper. Lack of vegetation and stability of the landscape over time facilitated reliable viewshed calculation. A possible impact of visibility on geoglyph distribution was statistically tested by comparing the visibility index of points on geoglyphs vs. random terrain points. Similar tests were performed for the spatial variables elevation and slope degree. The results indicate that good visibility was an important criterion for the choice of place for new geoglyphs.