Former and current aerial photos were scanned at high
resolution (900 dpi) and the raster data were then transformed
into the S-JTSK Krovak East North Grid System, since a commonbased
reference frame had to be applied. The transformed data
were digitised using ArcGis 10.1 software. Polygons that were
visually distinguishable, were semi-automatic vectorise for each
data layer; the minimum polygon size was then corrected, to avoid
statistical discrepancies. In this study, polygons smaller than 10 m2
were excluded