Journal of Cultural Heritage 15 (2014) 183–195 Available online at www.sciencedirect.com Original article Cartographic heritage: Toward unconventional methods for quantitative analysis of pre-geodetic maps Gabriele Bitelli a , Stefano Cremonini b , Giorgia Gatta a,∗ a DICAM (Civil, Chemical, Environmental, and Materials Engineering), University of Bologna, viale Risorgimento 2, 40136 Bologna, Italy b BiGeA (Department of Biological, Geological and Environmental Sciences), University of Bologna, via Zamboni 67, 40126 Bologna, Italy a r t i c l e i n f o Article history: Received 11 February 2013 Accepted 16 April 2013 Available online 15 May 2013 Keywords: Pre-geodetic cartography Georeferencing methods Landmarks Old Po river delta Surveying a b s t r a c t Historical cartography all over the world is a fundamental part of Cultural Heritage, and it needs to be preserved from damage of its analogical support due to ageing. Regeneration of ancient cartography in digital form is an interesting way not only to preserve historical cartographic documents as Cultural Her- itage, but also to allow new chances of understanding and using the historical information they record. In such a way, modern digital techniques, in particular study of map deformations and map georeferencing, help in metric analysis of ancient cartography, and at last they appear to be useful for researchers to derive historical information for their studies, for example related to urban development or to geomor- phological and environmental topics. The present research would give an example of the usefulness of the digital regeneration of ancient cartography, but also an example of possible difficulties in correctly interpreting information preserved in historical cartography, especially the pre-geodetic one. The study subject consists in three contemporaneous pre-geodetic maps (late 16th century) from the ancient Po river delta area (Italy), by means of which a geometrically correct representation of those parts of the landscape, not preserved today because of sea erosion, was tried. In fact, standard georeferencing meth- ods, that use reference control points to compare historical cartography with the present one, in this specific case demonstrated to be not successful in describing the real location of disappeared landscape details with an adequate level of accuracy. For these reasons, in order to define which map among the others was the most faithful to the contemporaneous physical reality, a compound methodology, consist- ing of a three-step analytical process, is here applied to the three samples. Starting from measurement of sighting angles and distances applied to a number of landmarks, a splitting of the old maps in sub- areas, probably corresponding to the set of original surveyed zones, was performed. In the area of main concern, the use of absolute measurements was avoided in order to check the level of inner congruence of the representation. Finally, a new specific error index, that can also be applied to maps lacking an explicit graphical scale, is proposed to evaluate the map truthfulness degree. The proposed method can be applied to other similar examples from ancient cartography. © 2013 Elsevier Masson SAS. All rights reserved. 1. Research aims Historical cartography is a very useful source of geographical information, but frequently of non-immediate comprehension or not completely reliable. Today, digital regeneration of historical cartography allows the researchers new ways to study the ancient maps and interpret the related information content, in particular to come to a more profound comprehension of their construction method. Here, a non-standard analytical method of analysis of the metric properties of ancient maps is proposed and applied to three ∗ Corresponding author. E-mail addresses: gabriele.bitelli@unibo.it (G. Bitelli), stefano.cremonini@unibo.it (S. Cremonini), giorgia.gatta@unibo.it (G. Gatta). contemporaneous late 16th century maps, delineating the ancient Po river delta area (Italy). The suggested methodology is so differ- ent from those usually adopted that no references were found to be available in the dedicated literature, to compare it with previous experiences. The proposed approach can be applied to other similar samples of ancient cartography when a modern reference map is available. 2. Introduction Historical cartography is a fundamental – even if often poorly known – part of Cultural Heritage; it consists in the whole amount of ancient cartographic documents (not only maps, but also atlas, plan spheres, globes. . .) the history has brought us. Today, these documents are kept in many public as well as private cartographic 1296-2074/$ – see front matter © 2013 Elsevier Masson SAS. All rights reserved. http://dx.doi.org/10.1016/j.culher.2013.04.003