Evaluation of handheld scanner for digitization of cartographic heritage

Abstract

Researchers who use old maps to explore different historical periods and themes are often facing a serious problem in terms of unavailability of their digital copies that are of acceptable quality. The map collection of various heritage institution is mainly consisted of classic printed cartographic materials. The mentioned institutions usually have no capacity to digitize oversized archival items such as maps, due to lack of the appropriate equipment. The objective of this paper is to investigate an easy and cost-effective method for producing the digital versions of analogue maps, based on map scans captured using a hand-held scanner. Although handheld scanners are considered unsuitable for map scanning purposes, this paper seeks to explore the possibility of using these devices to produce the adequate georeferenced map image with a reasonable effort. The proposed method is compared with the common-used digitization procedure that involves conversion of hard-copy maps into the digital raster format using the large-format sheetfed scanner. The influence of ground control points quantity and transformation model type was also evaluated.Hand-held scanning resulted in an appropriate number of image files, covering the area of map sheet by overlapped narrow scan sections. The image mosaic was created and subjected to geometric quality assessments and statistical analysis. Results from georeferencing tests showed that the successful use of a hand-held scanner for the purpose of paper map conversion into digital format depends on the minimization of distortion effects using suitable geometric transformation method. If this approach is applied correctly, most users will be satisfied with the results obtained by hand-held scanning and will be able to correctly display the content of digitized cartographic material alongside other georeferenced digital data.