Late Renaissance survey techniques revealed by three maps of the old Po river Delta.

This research was performed on a set of three maps depicting the Po river delta area (Northern Adriatic Sea, South of Venice) at the end of the 16th century. They were drawn by three famous land surveyors, today preserved in the Venice State Archive. The maps were mutually cross-compared in order to understand some late Renaissance land-surveying techniques. The kinds of evidence taken into account consist of technical signs preserved either in the palimpsest of the maps or in their final drawing. The meaning of some of the signs is explained by the Authors themselves in the legend or in the accompanying notes, whereas the meaning of other ones can be inferred by Fabri’s methodological textbook, containing the description of a new topographical instrument which he invented and used. All of these signs highlight a very interesting class of information related to the hidden steps of pre-geodetic map construction, which up to now is still poorly known and studied. Up to nine classes of peculiar evidences are recognized and indicated as analytical tools for a correct interpretation of each ancient cartographic sample .