Are Portolan Charts and Portolan Mile Geometrically Rooted in Classical Antiquity? A Cartometric Analysis of al-Shirazi’s “Greek Map” and the <i>Pisane, Lucca, Avignon</i>, and <i>Cortona</i> Charts
Bibliographic record
Abstract
Some of the earliest-made known portolan charts ( Pisane, Cortona, Avignon, and Lucca charts) and Qutb al-Din al-Shirazi’s schematic (1282) resembling “a map of the Mediterranean that was drawn by the sages of Greece and the ancient geometers” were cartometrically analysed. The results show that the Mediterranean was drawn nearly identically on the Carte Pisane and Lucca chart and that the preserved fragment of the Avignon chart is somewhat of an intermediate step between the Pisane–Lucca model and Pietro Vesconte’s model. The coasts of al-Shirazi’s schematic fit well with the Pisane and Cortona charts, whereas its 40×30 grid is similar in size to the grid drawn on the Pisane and Avignon charts. The length of its sides along the latitude φ = 36° (125 km) corresponds to 100 portolan miles ( miglia) and a 2-degree interval along the parallel φ = 36° according to Ptolemy’s incorrect estimation of the Earth’s size. Hypothetically, such a misunderstanding could have occurred if a late medieval cartographer (unfamiliar with the differences between spherical and Euclidean geometry) erroneously combined different spatial datasets from classical antiquity by unwittingly superimposing Ptolemy’s longitudes onto maps or charts made according to Eratosthenes’s correctly obtained size of the Earth by treating them as distances.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.005 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.004 | 0.007 |
| Science and technology studies | 0.001 | 0.006 |
| Scholarly communication | 0.006 | 0.004 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.008 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".