Balletti, Caterina 
ANALYTICAL AND QUANTITATIVE METHODS FOR THE ANALYSIS OF THE GEOMETRICAL 
CONTENT OF HISTORICAL CARTOGRAPHY 
Caterina Balletti 
DIIAR Dipartimento di Ingegneria Idraulica, Ambientale e del Rilevamento 
Sezione Rilevamento - Politecnico di Milano 
P.zza Leonardo da Vinci 32 — 20133 Milano 
balletti@brezza.iuav.it 
Working Group V/5 
KEY WORDS: : historical cartography - plane transformations - geometrical analysis - geo-referecing 
ABSTRACT 
The preliminary remark to the research described in the paper is the utilization of GIS for the management and the 
analysis of geographical-territorial data in their historic-temporal evolution, or rather to arrange historical information 
according to a key of spatial reading. 
In the development of a territory the historical cartography has had a deciding role. 
This means the necessity of getting data and informations from maps not only temporally arranged but even spatially 
referenced. 
The historical maps, however, for their metrical and semantic characteristics, are rather difficult to reference with the 
commonly used procedure. Often times in fact, they contain topographical and not metrical information and their 
insertion into a GIS is actually impossible. 
The aim of the research is to recover the metrical content in historical maps (particularly portolan charts, Isolari, 
perspective views of towns of XV-XVI century) using analyses which lead to a definition of a methodology for the 
quantitative analysis of historical cartography. 
This implies to use procedures that treat of: 
e global transformations: such as projective, affine, Helmert, polynomial transformation; 
e local transformation: such as finite element transformation, point based or feature based warping. 
Historic cartography has been, for long time, a subject of study by the historians and therefore, it has been considered as 
an archive document, a testimony of a certain period in the history of a territory, of a city. The study initiated and 
proposed in this paper faces, rather, the historic cartography according to an approach which is typical of the current 
cartography: extract territorial information which has been spatially referenced. 
The historic cartography, within the problems of using the GIS, is surely a field in which the questions relating to the 
referencing assume great interest. 
But how is it possible to geo-reference ancient charts? Often times they present some common characteristics such as: 
an uncertain metrical content 
a non definite system of reference 
representational scale 
unknown unit of measure 
an approximate projected system, 
non definite surface of reference 
not recognizable projective system: 
semantic content difficult to interpret. 
Such characteristics in the maps and charts from varying eras are found in greater or lesser measures, and consequently, 
it is necessary to make specific considerations when faced with each and every individual map. 
A map has different levels of accuracy, planimetrical, topographical, proportional, conventional, hierarchical, which are 
to be distinguished and to which the reader has to adapt according to the function that the map assumes: in a sea chart, 
distances, lands and bearings are characterized by a high accuracy. Harbors and mouths are positioned correctly and, 
often, magnified as regard the graphical scale of the chart. Instead, coasts are represented in a conventional way, such as 
the topography of the hinterland (such as mountains or representative architectures of a place). 
So there are two different categories: 
  
30 International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B5. Amsterdam 2000. 
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