Triangulating the Past – Recovering Portugal’s Aerial Images Repository

Although traditional and web map producers strive to deliver up-to-date products and old aerial photographs do not fit in their concept, other users are rather interested in old aerial images and in temporal series. In Portugal, aerial surveys for mapping purposes started by the late thirties of the twentieth century as documented by the oldest existing aerial photos collection in the archives of the IGEOE in Lisbon. Being the oldest visual witnesses of the country, the relevance of the information they contain is unquestionable. The objective of this project is the recovery of an important national aerial photographic heritage hibernating in analogue format in the archives. In a test block, strategies to recover radiometry and spatial orientation were developed and successfully tested in order to make the photos accessible and workable by the modern scientific community and by the general public. A photo-geographic database has also been organized and made available.