A New Interpretation of Ptolemy's Germania Magna: Employing Computer-Assisted Image Distortion of a Medieval Map by Donnus Nicolaus Germanus to Examine Post-Glacial Geodynamics in Europe

Note about the Germania Magna Research Project on Zenodo:

This contribution to the repository presents the current main publications of the geodynamic modelling project. As part of an actively evolving model, its content adapts to the current development stage and serves as the project’s central version control and documentation platform. The model is progressively advancing from an initially descriptive approach toward a more rigorous mathematical, geometric, and cartometric formalisation.

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The New (v9) Geodynamic Model Description for Ptolemys Germania Magna

based on (Mildner, S. (2026). Geodynamic Reinterpretation Model for Ptolemy’s Germania Magna: General Model Description, Cartometric Foundations, (v8). EarthArXiv (Preprint). https://doi.org/10.31223/X5KB51)

The reconstruction of spatial coordinates from Claudius Ptolemy’s Geographike Hyphegesis (c. 150 AD) for Central Europe has historically been hindered by large and spatially autocorrelated residual errors. The prevailing geodetic-cartographic consensus interprets these discrepancies primarily as the cumulative result of ancient measurement inaccuracies and medieval copyist distortions. This preprint presents Version 9.0 of an alternative, quantitative framework that treats the residuals as the cartometric expression of real, geologically recent landscape transformation.

The model combines two explanatory layers. First, the northern reference line — the coastline of the Oceanus Germanicus — lay approximately 120 km further south during antiquity than today, placing it near the latitude of Eberswalde. North of this line existed not open sea but an extensive amphibious zone of marshes, lagoons and reticulated waterways. Second, significant post-Ptolemaic crustal deformation occurred in the mid-sixth century AD, driven by reactivation of the Caledonian Deformation Front under Alpine compression, with a possible cometary or impact trigger. Using GIS-anchored affine transformations and a rigidly constrained kinematic block-deformation approach (global scaling factor ≈27–28 km per Ptolemaic degree), the model demonstrates that the observed residuals are mathematically coherent with large-scale block movements rather than random error.

Two principal deformation modes are identified. The Elster-Lusatia geographic cluster is interpreted as a translation-glide block that moved eastward relative to the rigid Lausitz backstop along a Zechstein décollement. With the identifications of Leukaristos (Finsterwalde), Arsonion (Senftenberg zone) and the revised Carrodunum site (Bernsdorf area), the six-point cluster yields a highly significant displacement of ∆λ = −88.9 km (t = −15.0, p ≪ 0.001, df = 5). The Arsonion location marks the décollement tip, completing the kinematic picture of initiation, propagation and arrest. Concurrently, the Sudete Mons / Thüringer Wald block underwent a rigid dextral rotation of approximately +35° about the Waltershausen universal pivot (10°33′E / 50°53′N), preserving inter-endpoint distances within 2 %.

A central innovation is the Unified Abnobae Mons hypothesis: the Ptolemaic Abnoba Mons is reinterpreted as a single coherent pre-deformation crustal block comprising the modern Taunus, Odenwald, Spessart, Rhön and pre-Vogelsberg basement. Fragmentation into today’s separate ranges resulted from a sinistral counter-rotation of its southern portion about the same Waltershausen pivot. Pre-deformation positions of the Rhenus and Danubius sources lay only ~26 km apart, in close agreement with Mercator’s 1569 representation. Internal proportions within Ptolemy’s coordinate system independently corroborate the identification of the Vistula Fluvius with the Lusatian river system rather than the modern Polish Vistula.

Version 8.0/9 introduces four substantive advances. A new Part VII establishes early-modern cartographic traditions as palaeodrainage archives. Systematic comparison of Mercator’s Europae Tabula IIII (c. 1578) with geological evidence demonstrates that the depicted western arm of the ancient Vistula preserves the Senftenberger Elbelauf — a Miocene to Early Quaternary northward palaeodrainage from the Dresden–Ottendorf-Okrilla area toward the Oder and Baltic Sea. This yields a transferable methodological paradigm termed palaeodrainage cartometry.

Second, parameter parsimony is formalised: the complete kinematic model operates with exactly nine free parameters — six affine coefficients, one latitude-bias gradient, one Elster-Cluster translation scalar, and one rotation angle — none of which are locally tuned. This parsimony makes the 29–49 % out-of-sample RMSE improvement robust against overfitting critiques. Third, Carrodunum is revised to the Bernsdorf area at the mechanically coherent onset of strain partitioning. Fourth, three new falsification tests (T36–T38) are added, including an archaeological test at Bernsdorf, direct verification of the Mercator–Senftenberger Elbelauf correlation, and a transferability test to other regions of the Ptolemaic gazetteer.

The model is mathematically overdetermined, subjected to formal out-of-sample blind testing, and generates 38 explicit, testable predictions across geochronology, geophysics, hydrogeology and archaeology. All data, code and the complete gazetteer are provided for full computational reproducibility. The work is presented as a working hypothesis intended to stimulate targeted empirical testing rather than as a definitive reconstruction.

Projektwebsite: https://www.ancientmaps-geography.com

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A New Interpretation of Ptolemy's Germania Magna: Employing Computer-Assisted Image Distortion of a Medieval Map by Donnus Nicolaus Germanus to Examine Post-Glacial Geodynamics in Europe

based on Mildner, S. (2026). A New Interpretation of Ptolemy’s Germania Magna: Cartometric, Geodynamic, and Historical Evidence for a Long-Term Transgression and Post-Antique Regression of the Oceanus Germanicus in Central Europe (Version 5). EarthArXiv (Preprint). https://doi.org/10.31223/X5313T

This paper revises and extends the author’s earlier interpretation of Claudius Ptolemy’s Germania Magna (c. 150 AD) by combining a cartometric analysis of the medieval map redaction of Donnus Nicolaus Germanus with evidence drawn from geodynamics, palaeohydrology, palynology, archaeology, and historical chronology. Its central thesis is that the apparent discrepancies between Ptolemy’s coordinate system and the modern Central European landscape are not primarily the result of ancient measurement error, as the prevailing geodetic-rectification school has assumed, but the cumulative product of two superimposed factors: a substantial, geologically recent transformation of the landscape itself, and the inevitable cartographic distortion that arose when medieval and early-modern editors re-projected Ptolemy’s coordinates onto an already changed terrain without recognising the underlying shift. The most consequential change concerned the coastline of the Oceanus Germanicus. During antiquity, this coastline ran approximately 120 km south of its present position, just north of present-day Berlin, at the latitude of Eberswalde. North of this line stretched not open sea in the modern sense, but a wide amphibious zone of marshes, reed flats, shallow lagoons and reticulated waterways — a landscape that on approach from the sea offered no clear shoreline at all. Within this framework, the Vistula Fluvius of Ptolemy corresponds not to the modern Polish Vistula but to the Lusatian river system of the Schwarze Elster, Spree and Oder; the Asciburgius Mons corresponds not to the Sudetes but to the Fläming and its south-eastern foothills; and the southern boundary river that Ptolemy calls Danubius may, on a revised reading, correspond to the modern Main rather than to today’s Danube, with the Abnoba Mons of his text identified with the Taunus rather than the Black Forest. The hypothesis advanced here is that the relevant landscape transformation occurred in geologically recent time — most plausibly during a window centred on the midsixth century AD — and was driven by a late-stage reactivation of the Caledonian Deformation Front (CDF) and adjacent structures of the Trans-European Suture Zone under the compressional regime of the closing Alpine orogeny, with the possibility of an impact or airburst trigger of cometary origin that may have catalysed the deformation. The proposed framework offers a unified explanation for the archaeological settlement hiatus of the fifth to seventh centuries, the abrupt collapse of arboreal pollen curves in the same window, the Late Antique Little Ice Age now widely recognised in tree-ring records (Büntgen et al., 2016), the political collapse of the Thuringian kingdom in 531 AD, and the subsequent Slavic re-colonisation of an emptied and ecologically reset landscape.

Projektwebsite: https://www.germania-magna.de,

based on the earlyer German PREPRINT title Mildner, Sven. (2020). Die Neuinterpretation der Germania Magna des Claudius Ptolemaios durch Sven Mildner - mit Hilfe computergestützter Bildverzerrung einer mittelalterlichen Kartendarstellung des Donnus Nicolaus Germanus - und Betrachtungen zur postglazialen Geodynamik Europas, 10.23689/fidgeo-5907. (engl. The Reinterpretation of Claudius Ptolemy's Germania Magna - with the aid of computer-assisted image distortion of a medieval map by Donnus Nicolaus Germanus - and considerations on the postglacial geodynamics of Europe)