SCANNING OPTIONS AND CHOICES IN DIGITIZING HISTORIC MAPS 
M. Daniil * 1,2 ’ a , V. Tsioukas l 2,b , K. Papadopoulos 2,c , E. Livieratos 3 ' 2 ' d 
1 Demokritos University of Thrace, Dept, of Architecture, Xanthi, Greece. 
2 National Centre for Maps and Cartographic Heritage - National Map Library, Thessaloniki, Greece. 
3 Aristotle University of Thessaloniki, Dept, of Surveying Engineering, Thessaloniki, Greece. 
a miltos@maplibrary.gr; b vtsiouka@arch.duth.gr; c kostas@maplibrary.gr; d livier@topo.auth.gr 
WG 4 - Digital Image Processing 
KEY WORDS: Scanner, Photography, Cartography, Historical maps, Cartographic Heritage, Digital map archives 
ABSTRACT: 
The introduction of modem digital imaging techniques in historical cartography, especially in documenting old map collections, 
meets the need for extending and complying image processing and relevant photogrammetric tools in the analysis of antique maps in 
the context that digital photogrammetry intersects the modem theories in digital treating of old maps. 
In this paper we discuss some aspects in controlling the geometric features of the scanned images of antique maps in terms e.g. of 
linear, angular and areal deformation. Collateral effects influencing the scanned map image are also talked namely the statistics and 
the image quality of the output map images with respect to the original map and/or the “reference” digital best scanned image. 
1. INTRODUCTION ■ In some cases are not directly accessible. 
m 
In the second group the following items can be assembled: 
■ The map-scale, usually small and loosely defined. 
■ The drawing method, the projective properties and 
the associated map deformations, which in most of 
the cases are veiled especially in the pre-scientific 
cartography. 
■ 
All the above -and obviously some more to be identified or de 
termined- led us to the idea that the use of photogrammetric me 
thods and techniques are worth to be extensively tried and 
tested in historical map processing, mainly the digital counter 
part, which is a new trend in modem cartographic culture 
(Livieratos and Myridis, 1999; Livieratos et al., 1999). Old 
maps cannot be treated just like any other hardcopy printed on 
paper or other relevant supporting material. Most of them are 
not well preserved and properly stored. This makes their digital 
transformation a not easy job since the conventional approach 
is not proper. In the conventional approach applied in modem 
map hardcopies, digitalisation is the result of a direct contact of 
the original with the scanning device without taking into ac 
count the overall technical specifications of the device. This is 
not the case for old maps due to the very concrete reasons 
mentioned above. 
In order to face the digital treatment of old maps considering 
the particularities of the issue, the following scheme of actions 
could be attempted. The old map can be digitised in two modes: 
■ In the traditional direct mode (DM). 
■ In the photogrammetry-prone indirect mode (IM) 
involving an a-posteriori direct digression. 
These two basic modes are in fact the acquisition procedures in 
order to store the digital files of old maps (dfs) for the shake of 
their documentation and archiving but also for their further ana 
lysis and interpretation. 
varying. 
In the modem era of mapping, photogrammetry was always 
interacting with cartography in the field of mapmaking. Since 
the first processing of aerial photographs in the framework of 
analog photogrammetry in the past century, maps became more 
precise depicting in all possible scales parts of the real world 
space. Modem technology using computers, digital photogram 
metry (Schenk, 1999) and specialized hardware and software in 
creased the above mentioned interaction and support the emer- 
tion of new domains of science and technology bom from the 
intersection of already well founded fields as it is digital photo 
grammetry and cartography in all its folds, especially the digital 
one. Although historical maps are not of course based on photo 
grammetric information and at a first sight seems that there is no 
relevance at all between the two disciplines (at least for maps 
before the era of photogrammetric mapping), this paper will at 
tempt to introduce a new view and understanding in how histo 
rical cartography and digital photogrammetry could meet and 
produce new products assisting the analysis and the interpreta 
tion of many hidden mysteries of old maps at least as far as their 
geometric content is concerned. 
2. THE BASICS OF THE IDEA 
Among the very special and particular characteristics of old 
maps one could pick the following, which are taken here in two 
groups for the shake of the example. The first concerns the de 
gree of alteration of the material and the second the geometric 
properties of the content. 
In the first group one should stress the fact that, generally spea 
king, old maps: 
* Are indeed sensitive as material objects. 
■ They are often partially damaged in various ways and 
degrees. 
■ The thickness of the map-sheet in its different kinds is 
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