On Determining the Length of a Ptolemaic Degree – Supplement to the Reinterpretation of Germania Magna (doi: 10.31223/X5313T)

The realignment of the Germania Magna map according to this interpretation results in a new value for the length of a Ptolemaic degree. The following explanation is intended to make the calculation steps leading to this value easier to understand. For the derivation, we first consider the two rivers that border Germania Magna to the east and west, for which Ptolemy recorded the coordinates of their estuaries into the Oceanus Germanicus.


_File: "Overlay_geograf.Einheiten_zur_Germania Magna Neuinterpretation nach Sven Mildner.kml":

First draft of a map overlay featuring the geographical units of Germania Magna, adapted to the area of the Federal Republic of Germany and represented in a modern WGS84 coordinate system for Google Earth

(erster Entwurf eines Kartenoverlays mit den geografischen Einheiten der Germania Magna, übertragen auf die Bundesrepublik Deutschland bzw. auf ein modernes WGS84-Koordinatensystem für Google Earth)

Version 3 (01.05.2025) - Changelog:

• Improved alignment of Albis Fluvius in the middle Elbe region, south-east of Magdeburg
• [Revised representation] of the lower course and/or the mouth region of Rhenus Fluvius, more closely aligned with the map overlay rather than the present-day course of the Rhine (see following graphic)
• Addition of the river “Vidrus Fluvius” to the overlay, corresponding to the map overlay, with its source near the Vogelsberg in Hesse (see following graphic)

Note: The source and mouth region of Visurgis Fluvius has been shifted northward according to the map overlay, compared to the original representation on the medieval map of Donnus Nikolaus Germanus.

more:  https://www.germania-magna.de/kartenoverlay-mit-den-geografischen-einheiten-der-germania-magna/

Version 4 (07.05.2025) - Changelog: 

• Improved alignment of Albis Fluvius "Variante B" in the middle Elbe region between Bitterfeld-Wolfen and Braunschweig/Celle, and Addition of "Variante C" in the middle Elbe region with Albis Fluvius corresponding with a part of modern river Mulde near Dessau (Sachsen-Anhalt)
• Addition of the river “Tibiseus Fluvius” to the overlay, modern Iser/Jizera (CZ)
• .kml-file is a Network-Link-KML

Version 5 (08.05.2025) - Changelog: 

• Changes of Version 4 (Netzwerk-KML) and Improved Alignment for Chalusus Flu. (now Havel) and Suebus Flu. (now Nuthe)
• Addition of some ancient settlements to the overlay (Alisum, Amisia, Asciburgium, Budorigum, Budorgis, Budoris, Calisia, Carrodunum, Limiosaleum, Lugidunum, Mediolanium, Nomisterium, Parienna, Stragona)
• .kml-file is an Offline-KML

Version 6 (10.05.2025) - Changelog: 

• Improved Alignment for Vistula Flu., Suebus Flu., Viadua Flu. and Chalasus Flu.
• Addition of ancient settlements Colancorum, Lupfurdum, Mersovium and Susudata
• Addition of "Ziltendorfer Niederung"
• Some points of interesst now have additional informations in the description text for a better understanding

Note: The drawn course of the Chalasus Fluvius here roughly follows the Mercator map. According to the depiction of Germania Magna on the map by Donnus Nikolaus Germanus, the mouth area of the Chalusus Flu. is located approximately 15 kilometers further west, i.e., near Vehlgast/Kühlhausen or in the direction of Havelberg. This could indeed also indicate a change in the course of the river in antiquity, which becomes evident when comparing both maps and for which there are also further indications that such a change could actually have occurred. Consequently, it would then also be reasonable to assume that both maps might not depict Germania Magna at the same point in time, but that the course of the Chalusus Flu. on each map was recorded independently at different times. The question could still be whether a main channel was actually discernible in the mouth area here, or whether it was rather a branched delta. The course of the rivers drawn on the map, however, it seems, could also have been oriented much more directly along the course of the already existing subglacial meltwater channels.

Version 7 (12.05.2025) – Changelog:

• With this version, several of the Germanic and Sarmatian tribes are now located on the map.

Version 8 (12.05.2025) – Changelog:

• Further information was added to the description, initially regarding the Sarmatian tribes.

Version 10a,b,c (15/20.09.2025) – Changelog:

• Further information was added to the description, initially regarding the Sarmatian and Celtic tribes.
• Settlements and tribes with a possible Celtic name origin are now marked with a black symbol, Germanic tribes with a blue one, and Sarmatian tribes with a yellow one. (dt.: Siedlungen und Stämme mit einem möglichen keltischen Namensursprung werden nun durch ein schwarzes Symbol gekennzeichnet, germanische Stämme durch ein blaues und sarmatische Stämme durch ein gelbes Symbol)

Version 11 (21.09.2025) – Changelog:

• For orientation, a new layer containing geological information relevant to this reinterpretation was added, beginning with the Late Paleozoic volcanic centers in Central Europe and a possible fault zone between Kamenz and Görlitz

Version 12a/b (24.12.2025) – Changelog:

• rechnerische Bestätigung der Verortung des Römerlagers Aliso (bekannt durch die Beteiligung der hier stationierten Truppen an der Varusschlacht) bei Haltern am See, wie bereits durch andere Autoren beschrieben und durch die Bestimmung eines ptolemäischen Breitengrades (siehe hier).
  
  mathematical verification of the location of the Roman camp Alisio (noted for its role in the Varus Battle) near Haltern am See by other authors, based on the calculation of Ptolemaic latitudinal distance (see here).