Georeferencing maps

Historical maps are both a source for places and borders and more, as well as a visualization aid for when that information is used. They lend immediate visual credibility to location based information. They are just neat to look at! For them to be useful, though, they need to be adjusted to a common map projection. Georeferencing is a tool for that purpose. This process can be fairly straightforward for recent maps that are based on a well known projection. For older maps, predating accurate metrology, this process is necessarily error-prone with large uncertainties. xplris has a build-in georeferencing mechanism that allows anyone to add any map to the platform for use as a source and for visualization.

• Location based information (points of events, borders of countries, ...) are based on textual descriptions in source material or graphical representations on historical maps. In the latter case, the source maps need to be georeferened as best as possible given the quality of the reproduction. Locations are then derived from the original position in the map and projected to latitude and longitude coordinates along with uncertainty estimates based on the accuracy of the map and the distortion of the map projection.