Bernie Jenny | Map Design

Map Distortion and MapAnalyst

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    Distortion grid and position differences for the London Underground map

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    Distortion grid for the London Underground map on a Mercator projection

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    Isolines of local scale for the London Underground map

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    Displacement vectors for the London Underground map

I develop methods for analysing the planimetric distortion and accuracy of old maps and map diagrams. MapAnalyst is a specialised software for the geometrical analysis of map diagrams and old maps. It can generate distortion grids, displacement vectors, and isolines of scale and rotation to illustrate local map deformation.

MapAnalyst was reviewed in the journal Cartographica and was judged "a great piece of software for analysing old maps, and one would expect MapAnalyst to be a welcome addition to the desktops of map researchers everywhere". MapAnalyst has been used by several map historians for the study of old maps.

Geometric Analysis of Cartographic Heritage

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Orange is a copy of black, but not blue: The displacement vectors of the Hassler and Nötzli maps coincide, the vectors of the Atlas Suisse are spatially unrelated. Analysis and visualisation with MapAnalyst (Data courtesy of Dr. Martin Rickenbacher, Federal Office of Topography swisstopo.)

Old maps are increasingly used as a source for historical research. As with every source, when old maps are georeferenced and information is extracted for historical studies, the accuracy and reliability of the geometric and semantic information must be assessed. A series of geometric transformations can transform control points of a modern reference map to the coordinate system of an old map. Based on these transformed points, the planimetric and geodetic accuracy of the old map can be computationally analysed and various visualisations of space deformation generated. The results are graphical representations of map distortion, such as distortion grids or displacement vectors, as well as statistical and geodetic measures describing the map geometry (e.g., map scale, rotation angle, map projection). The visualisations help the map historian to assess the geometric accuracy of historical geographical information before using the data for geo-historical studies. The visualisations can also provide valuable information to the map historian about the history of a particular map and its creation.