Hi ha algun exemple a Internet De la creació de mapes plotejant les coordenades dels punts de la costa, dels diferents paisos i llavors unint els punts?
jo el vaig trobar una vegada amb google, però ara no ho trobo

Ptolemeu no va deixar almenys no han perdurat cap mapa dibuixat el que queda és la geografia de Ptolemeu amb les longituds i les latituds de totes les ciutats de l'Imperi Romà Uns monjos al segle 13 i 14 van posar aquestes coordenades sobre un paper i unint. les ciutats de la costa van assolir fer un dibuix d'Europa i Àfrica o sigui del món conegut les coordenades. que tenia la geografia de Ptolemeu la latitud estava amb una precisió molt bona ja que és l'alçada de l'estrella polar al Pol Nord (al Pol Sud no sé quant van trigar a trobar la Creu del Sud) Però la longitud es calculava per estima, llavors hi ha errors força grans en longitud, que és el que causa aquests errors en el dibuix en els mapes de Ptolemeu

Els portolans mallorquins estaven fets presumiblement marcant una triangulació amb el compàs i encara que a tota la Mediterrània Hi ha una desviació del Nord és gairebé la mateixa a tot arreu i els van sortir uns mapes gairebé perfectes.

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Absolutely! You're describing a fascinating and historically significant aspect of cartography. The process of plotting coordinates and connecting them to form a map is fundamental, and what you recall about Ptolemy's Geography being used this way by later monks is spot on.

It's common to have trouble finding something specific you saw on Google before, especially if the search terms aren't just right. What you're looking for is often referred to as:

• Reconstructions of Ptolemy's maps from his coordinates.
• Plotting ancient coordinates to recreate maps.
• Digital reconstructions of historical maps.

Reconstructing Ptolemy's Maps Today

Yes, there are definitely examples on the internet of exactly what you described! Modern cartographers, historians, and digital humanities projects have undertaken precisely this task: taking Ptolemy's Geography (his list of latitudes and longitudes) and plotting them using modern software to visualize the world as he described it.

You can find numerous examples by searching for terms like:

• "Ptolemy map reconstruction coordinates"
• "Ptolemy's Geography modern mapping"
• "Ptolemy coordinates visualized"
• "Digital Ptolemy maps"

Many of these projects highlight the errors in longitude that you correctly identified, showing how the Mediterranean appears stretched or distorted compared to modern maps, while the relative latitudes are often more accurate.

Here's an example of what you might find, showing a common visualization that illustrates these errors:

• Image Search for "Ptolemy map reconstruction coordinates" (You'll see various renditions, some overlaying modern coastlines to highlight the discrepancies).

The Medieval Monks and Ptolemy

Your understanding of the medieval context is also accurate. While Ptolemy himself didn't leave surviving drawn maps, his Geography provided the raw data. When his text was "rediscovered" and translated into Latin in the early 15th century (notably by Jacobus Angelus in 1406, though earlier Byzantine scholars knew of it), it was indeed scholars and cartographers (often associated with monastic or scholarly centers) who used these coordinates to draw maps for the first time based purely on mathematical principles, rather than just empirical observation or portolan charts. These early Renaissance maps, inspired by Ptolemy, marked a significant shift in cartography.

Portolan Charts vs. Ptolemaic Maps

You've also hit on a crucial distinction with your mention of Majorcan portolan charts. You're absolutely right:

• Portolan charts (like those from the Majorcan Cartographic School) were empirical, based on compass bearings and estimated distances (dead reckoning) from actual voyages. They were incredibly accurate for the Mediterranean and Atlantic coasts they covered, primarily because they focused on relative bearings and distances between known points, rather than absolute coordinates. Their characteristic "wind roses" and rhumb lines allowed navigators to plot courses effectively. The "deviation from North" you mention for the Mediterranean would have been largely consistent across the chart, leading to surprisingly accurate local representation.
• Ptolemaic maps, on the other hand, were theoretical, based on a grid of absolute latitude and longitude. While revolutionary for their time, the inaccuracies in longitude (due to the difficulty of precisely measuring it before accurate chronometers) led to distortions, especially over large east-west expanses like the Mediterranean.

It's a fascinating contrast between two different, yet complementary, approaches to mapping the world in pre-modern times!

I hope this expanded explanation helps you reconnect with the information you were looking for and enriches your understanding of these historical mapping techniques.