Rectify the river, rectify the map; geometry and geovisualization of Adige river hydro-topographic historical maps

Analysis of historical maps is useful for purposes not only in a qualitative but also in a quantitative way, whereas the latter serve the purpose of assign a geometrical content to early maps, useful for a comparison with current maps. The main problem with old maps depends on their unknown projection and/or their lack of geometric accuracy. Thus, the evaluation of planimetric accuracy (through a calibration) represents a previous analysis helpful for a consequent standard geometric correction. This paper analyses as a case‐studies two fine‐scale historical maps of Adige river (1802‐1850) through three steps: firstly, the accuracy has been analyzed; then, we have performed a local geometric transformation suitable with linear topologies; and, finally, we have set up map‐tiles/mashup for web mapping