Comparing historical and contemporary maps - a methodological framework for a cartographic map comparison applied to Swiss maps

ABSTRACT

Topographic maps are powerful tools for the purpose of identifying land use and cover change (LUCC) as they are among the most reliable representations of past landscapes for the time prior to the existence of aerial photography. In light of the increased availability of historical maps, we argue that there is a need for a standardized process to assess map comparability in a systematic way in order to avoid, or at least minimize, the detection of spurious landscape changes due to incompatible map series. A full understanding of map quality, background and error distributions is fundamental to attain reliable LUCC results. The conceptual framework presented in this study considers the context, distortion and cartographic generalization of topographic maps. Furthermore, it includes an approach to homogenize the level of generalization of landscape elements (e.g. forests) from maps with different scales. To demonstrate its application, we assessed the comparability of seven topographic maps from Canton Zurich covering a time span of 336 years (1664–2000). Overall, for the maps of Canton Zurich, a wall-to-wall comparison of forest cover based on the topographic maps presented here can be problematic for the oldest map from 1664. Based on the results, a wall-to-wall comparison with the later maps is not recommended, due to its substantial distortion. Yet, after re-generalization of natural landscape elements, such as forests, a comparison based on landscape indices is possible, even for the oldest map. Furthermore, our results demonstrate that maps from the mid-19^th century onward possess an acceptable level of accuracy. This framework can be applied to a wide range of maps at regional, national, or global levels, providing the opportunity to look at land cover history over multiple centuries.

KEYWORDS:

• Historical maps
• conceptual framework
• cartographic generalization
• map distortion
• Canton Zurich
• Switzerland

Acknowledgments

We gratefully acknowledge support by the Swiss National Science Foundation (SNSF) in the project Forest dynamics in Switzerland (FORDYNCH)—pattern, driving forces and ecological implications (Grant No. 200021-143242). We would like to thank Krzystof Ostafin for his support with the semi-automated feature extraction for the map from 1970, Ruedi Bösch for his comments on the alpha-shape topics and Matthias Bürgi for his input and comments on the manuscript. Thanks to Sarah Radford and Curtis Gautschi who kindly improved the English.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

Supplemental data for this article can be accessed here.

Additional information

Funding

This work was supported by the Swiss National Science Foundation (SNSF) [200021-143242]