Proposta per la realizzazione di un catalogo aerofotografico dei ghiacciai italiani

Proposal for the realization of an inventory of aerial photographies of glaciological interest in Italy

Abstract

Photography is an important tool to study the glacierised areas of the Alps and to monitor glacier changes: since 1979, members of the Comitato Glaciologico Italiano collect and catalogue in special archives photographic images of Italian glaciers taken during annual field trips or research. Another important iconographic heritage on Italian glaciers has been built up during the last decades, due to the increasingly frequent use of remote sensing imagery for scientific and applied studies of the Earth's surface. We refer to images from aerial photography, which proves itself as an irreplaceable tool for several reasons: 1) it allows a unitary and homogeneous view of extended parts of an area, including those of difficult accessibility on the field; 2) if several aerial photographs of the same area are spread over a period of time, multitemporal photo-interpretative analysis are possible; 3) coeval images of an extended portion of a region allow evaluations concerning climatic changes; 4) high-definition remote sensing is a primary tool in the evaluation of hazard and risk connected to dynamically very active physiographic units such as glaciers. On the basis of the above-mentioned considerations, a project has been developed to perform an inventory of aerial photographs of glaciological interest in Italy: they constitute a conspicuous and valuable heritage, sometimes difficult to utilise because of images' dispersion and disorganisation. The recording form of the database has been drawn up to collect both technical data concerning the aerial photographic shots (Dati sui volo = flight data; Caratteristiche dell'immagine = image characteristics), and useful information to reconstruct the morphological evolution of the glacier (= Aspetti Morfologico-Ambientali). Special attention has been devoted to the search for «objective» standards of description, in order to make survey and checking of data easy and to allow comparison of data from different researchers. Taking into account the considerable amount of available data, during the present experimental stage of the work, the «aerial photographic strip» has been chosen as the basic unit of cataloguing. This unit allows differentiation of series of aerial photographs by date, each series showing unique features, due to frequently changing meteorological and environmental situations in the glacierised areas. Extensive analysis of aerial photographs also enables sorting of images by quality: under certain meteorological circumstances there are obstacles to aerial photography interpretation. Aerial photographs of the Miage Glacier (a major glacier in the Western Alps, Mont Blanc Massif, Italy) have been collected and catalogued in order to check the operation of the database (executed with Filemaker Pro by Claris Co.) and to show the functioning of the inventory of aerial photographs of glaciological interest in Italy. Browsing data from more than 250 photograms, related to 20 consecutive sets of aerial photographic shootings covering a 52-year time interval (1945-1997), proved to be a very useful tool to trace the recent dynamic evolution of the glacier. Variations in size and shape of the glacier (such as the remarkable advance of the '80s), emptying/filling episodes of the Miage Lake, and other glacial events relevant to geomorphological hazard evaluation in ice-marginal environments, have been singled out with great precision.