CARTOGRAPHIC "SIGNS" AND PHOTOGEOLOGICAL PARAMETERS: EVIDENCE OF NATURAL PROCESSES AND HISTORICAL MEMORY OF PLACES (VAL DI CHIANA AND UMBRIAN TIBER)

The theme of the conference of AIC in Gorizia is particularly stimulating and can raise issues interesting for research and interpretation in the historical cartography and beyond. The historical maps and aerial photos are two cognitive tools with an apparently different technical and interpretive approach, but are particularly useful for understanding the territory. The geologist and photo-interpreter, in fact, can make use of expertise and field data of various content and type to get to know the events that have affected the area. These reports are obviously reflected in the mapping. The overall result of knowledge, therefore, becomes structured, detailed and rich in information, that can be grasped from an attentive observation of "signs" that an old engraver and cartographer drew carefully or roughly on an ancient map. This instrument, besides the suggestion that it evokes, also represents a gap in time that has to be filled from a place between the scientific reconstruction and the current physical evidence. The "hatch art”, as it was defined by IGM, is almost always a faithful reproduction of the natural elements of landscape delineating morphological and hydrographic situations. Morphological evidence of neo-tectonics may be picked up unexpectedly in a landscape just drafted by an engraver cartographer. The morphological elements, in fact, were always considered significant topographical elements such as a watershed and natural boundaries. Often the limit of a region is more stable than the path of a river that delimits that region and that, in its development, abandons the "sign" of man, becoming the wreck of a morphogenetic process and memory of the human evolution. Human boundaries follow the physical boundaries of places and delimit relevant property and areas following the gradual changes in natural processes. Human memory intersects with that of the earth and events that they are involved in can be inferred both from historical maps as the latest aerial imagery, bearing indelible trace of processes past and present. The broad depression of Chiana valley, for example, is land of border and communication between the morpho-hydrographic of Tuscany and Umbrian territory. The pattern of the Tiber, between Todi and Anghiari, is strongly morphologically conditioned and conditioning the evolution of historical and environmental Umbria. The hydrographic history of these areas is natural recognizable in the old maps and in aerial photos and can help to develop hypotheses on the paleogeographic local evolution, by making use of ancient maps that are reflected in most modern representations and techniques of the land interpretation.