Naslov
Certain arguments against the hypothesis that portolan charts were genuine late-medieval cartographic products

Autori
Marelić, Tome

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, neobjavljeni rad, znanstveni

Skup
On the Origin and Evolution of the Nautical Chart, IV International Workshop

Mjesto i datum
Lisabon, Portugal, 25.05.2023. - 26.05.2023

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
portolan chart origins ; portolan chart accuracy ; terrestrial navigation ; Adriatic Sea

Sažetak
A sample of 12 representations of the Adriatic Sea on portolan charts, created between the late thirteenth century and the late sixteenth, as well as distance and bearing navigational data extracted from five portolani written between about 1200 and 1490, were subjected to a series of tests in order to examine their navigational applicability. The by-products of their results strongly suggest that it is highly unlikely that portolan charts were, in terms of their geometry, genuine late-medieval cartographic products. Firstly, the research results showed that Adriatic Sea basin renderings on portolan charts were probably the result of a deliberately applied map projection which was geometrically most similar to the modern conformal cylindrical (Mercator) projection. Secondly, the textual data on distances (expressed in portolan miles) and bearings (expressed in wind directions) contained in selected portolani do not represent the aggregated body of genuinely acquired measurements performed during late-medieval navigations, but that they were, most likely, extracted directly from portolan charts already in existence at the time. Thirdly, it was demonstrated that, during the 300 years of their continuous production, their accuracy was not improved, and their anticlockwise tilt was not chronologically aligned with the dynamics of magnetic declination across the research area. Moreover, it was explicitly demonstrated that bearing measurements that could have been performed aboard a ship (from a sailor’s perspective) cannot be used to create charts that display such levels of geometric accuracy, not only in the late-medieval period but in general. In the consecutive study, the cartographic representations of the Adriatic Sea basin on eleven (manuscript and printed) Modern Age nautical charts, made between 1538 and 1771, were subjected to a cartometric analysis in which their geometrical features were inspected. Additionally, four of them on which the graticules were plotted, were subjected to the analysis of their spherical coordinates, which was conducted in parallel. The results show that cartographers who produced printed charts in the seventeenth and eighteenth centuries never succeeded in surpassing the geometric accuracy of manuscript portolan charts from the sixteenth century, regardless of whether their charts contained graticules or not. According to the results and the historical context of contemporary technological development, it appears that in the era that preceded systematic hydrographic surveys, their authors had no other choice but to (partially) copy the inherited ‘framework’ of portolan charts as a reference model, and to implement certain localized trial and error modifications.

Izvorni jezik
Engleski

Znanstvena područja
Geodezija, Povijest, Geografija

POVEZANOST RADA