DigMap (MATLAB) - Digitization and scale correction of historical topographic maps

Abstract

This technical report presents DigMap (Digital Map Digitizer), a software developed to make the digitization of historical maps easier and more direct. The program allows saving the extracted data (contour lines or other elements) in text format, using the standard three-column structure x, y, z. The main goal is to address a common problem: the lack of original maps with an explicit scale (1:N), which prevents the direct conversion between image pixels and real-world measurements. The report describes the main functionalities of the software through application examples. The tools are intentionally simple, designed also for non-expert users, combining a manual approach with clear and reliable results. Available operations include: loading an image, defining a scale (temporary or final), interactive creation of contour lines, exporting metric data, building a digital elevation model (DEM), generating a point cloud with user-defined density, and finally importing and rescaling the cloud itself. The software was initially developed for the digitization of topographic maps produced in 1906–1907, used in a study of mud volcanoes (salse) in the Northern Apennines of Emilia-Romagna. In the future, further automation will be implemented.