The remarkably accurate representation of coastlines on late mediaeval portolan charts has garnered significant scholarly interest in uncovering the origin of their spatial data, with the prevailing hypothesis suggesting that they are authentic products of their time, created by synthesising numerous shipborne bearing and distance measurements. The pursuit of those answers also prompted the establishment and advancement of a cartometric approach, through which they can be attained with quantitative accuracy. This study is based on cartometric analyses and historical evidence, providing a comprehensive examination of the anonymous Carta Riccardiana portolan chart, presumably created by Pietro Vesconte between 1300 and 1325. It posits a paradigm shift regarding the late mediaeval origin hypothesis, tangibly indicating that the conventional geometry of portolan charts was likely developed by late mediaeval copyist-cartographers who utilised regional maps from classical antiquity, originally made in the projection of Marinus of Tyre calibrated to their mid-latitudes as inputs, which they partially scaled and gradually tilted, using a map in Ptolemy's first projection as a reference model. Concurrently, the article provides a historical overview of the most significant cartometric studies in the field, critically analysing their unique systemic parameters that have influenced various hypotheses regarding the origin of portolan charts – specifically, the systemically induced similarity with the modern map in the Mercator projection, which is, in the case of the Carta Riccardiana, at least, a misleading notion.

The research addresses the representation of selected Adriatic islands, subcategorised with respect to their size, on early modern nautical charts and geographical maps employing two concurrent approaches. The first approach inspects their positioning relative to one another and in absolute terms, and their visual appearance. Particular emphasis was placed on their dimensions in relation to a modern map, which were quantified utilising the Local Map Scale Index (LMSI). The second approach focuses on the toponymical content, and examines their distribution and varieties, including some notable aspects of naming certain islands. The findings indicate that small remote islands such as Palagruža and Pianosa were rendered as the most exaggerated, presumably due to their significance for terrestrial navigation, and that early modern geographical maps depicted islands larger than contemporary printed nautical charts. Research has established that most of the islands on old maps were designated by Venetian names rather than by the names used by their inhabitants, reflecting the influence of Venice as the dominant political and economic power in the Adriatic. In this process, greater emphasis was placed on naming the more important islands of the outer chain and the offshore islands relevant to maritime navigation, regardless of their size. Although the nature of these phenomenologically distinct map elements hinders the establishment of a convincing quantitative correlation and causal relationship between their manifestation and distribution, they are complementary as they collectively improve spatial orientation and reflect historical geographical understanding during the examined period. Consequently, the study aims to introduce a novel cartometric and analytical methodology to enhance the present understanding of island representations on early modern charts and maps overall.

Extensive cartometric analyses were performed on the portolan atlases of Pietro Vesconte (1313), Andrea Bianco (1436), and Battista Agnese (1538), along with their manually assembled composites and contemporaneously made portolan charts. The results indicate that none of the small-scale atlas sheets were fully aligned with the contemporary magnetic north, that they typically exhibit coastline contours mapped to different scales, and that the spatiums (50 miglia intervals) in Vesconte’s and Bianco’s atlases differ in length subsequent to the assembly of their composites. Consequently, the atlas sheets could not provide sailors with consistent navigational accuracy across the whole displayed area. Moreover, notable geometric differences can be observed between the composite of Vesconte's atlas and his 1311 portolan chart, as well as between the composite of Bianco's atlas and his smaller-scale chart bound in the same atlas, indicating that their creators had a limited understanding of their geometry. The discovery of cartometrically determined underlying mosaics of subsections encapsulated within their composites with accuracy twice as great—whose spatial extents have remained almost unchanged during more than two centuries of their production and geometrically correspond to portolan charts created before them—suggests that portolan atlases are medieval and early modern copies of earlier-made cartographic sources.

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.

Abstract Since the beginnings of nautical cartography in the Mediterranean region during the Late Middle Ages, the importance of nautical charts has grown beyond mere navigational purposes, especially during the early modern period. They became an essential medium for conveying an extensive array of socioeconomic information and messages, particularly as less expensive and easier-to-distribute printed charts began to replace their manuscript counterparts. Due to its immense geostrategic significance in integrating the Mediterranean framework with continental Europe, the Adriatic Sea and its surrounding areas have been the sole focus of numerous early modern charts. Featuring two primary ensembles, the chapter provides a comprehensive overview of the development of nautical cartography for the Adriatic Sea region from the late medieval era until the advent of systematic field surveys. With its most significant scientific and stylistic turning points explained in greater detail and supported by the most important cartographic examples, the first one focuses on the chronological development of nautical cartography as seen through a phenomenological lens. The second one focuses on the history of the discipline itself and provides readers a variety of insightful academic results that are further distinguished based on key methodological principles applied to the study of old nautical charts, both of the Adriatic Sea and beyond.

A sample of 12 representations of the Adriatic Sea on portolan charts, created between the late thirteenth century and the late 16th, were subjected to a series of tests in order to examine their navigational applicability. However, the by-products of their results strongly suggest that it is impossible that portolan charts were, in terms of their geometry, genuine late-medieval cartographic products. 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 which could have been performed aboard ship (from sailor's perspective) cannot be used to create charts which display such levels of geometric accuracy, not only in the late medieval period, but in general.

Seven portolan charts and atlases (including the anonymous Rex Tholomeus chart) made between 1311 and 1538 were cartometrically analysed. The findings indicate that their geometry was not improved chronologically and that the accuracy of Pietro Vesconte's charts (1311-13) was never surpassed. Portolan charts and atlases appear to be mosaics composed of subsections, each with variable metrics and accuracy levels that are, on average, twice as great in comparison to their Mediterranean and Black Sea areas (as a whole), and it is highly unlikely that they are genuine late medieval products, which is also supported by historical evidence. Their anticlockwise tilts fit well with the tilt of the Gibraltar-Antioch line on modern maps that closely approximate Ptolemy I and Ptolemy II projections centred near Gibraltar and with their meridian tilts for areas around Genoa. If late medieval Italian cartographers had acquired a collection of maps or charts from before the Middle Ages, it is theoretically feasible that they could have achieved the typical geometry of portolan charts by graphically combining their manuscript copies of large-scale regional maps in Mercator or Mercator-like projection, using a small-scale map in conic or pseudoconic projection (on which the convergence of meridians is displayed) as a template. Sept cartes portulans et atlas (dont la carte portulan anonyme Rex Tholomeus) publi & eacute; entre 1311 et 1538 ont & eacute;t & eacute; analys & eacute;s cartographiquement. Les r & eacute;sultats montrent que leur g & eacute;om & eacute;trie n'a pas & eacute;t & eacute; am & eacute;lior & eacute;e de fa & ccedil;on chronologique et que la pr & eacute;cision des cartes de Pietro Vesconte (1311-1313) n'a jamais & eacute;t & eacute; & eacute;gal & eacute;e. Les cartes portulans et atlas semblent & ecirc;tre des images en mosa & iuml;que compos & eacute;es de sous-sections dont les m & eacute;triques sont variables & agrave; l'int & eacute;rieur de chaque unit & eacute;, et dont les valeurs de pr & eacute;cision sont, en moyenne, deux fois plus grandes que celle de la M & eacute;diterran & eacute;e et de la Mer Noire (pris dans son ensemble), et il est tr & egrave;s peu probable qu'il s'agisse de produits de la fin du moyen-& acirc;ge. Leurs inclinaisons dans le sens inverse des aiguilles d'une montre correspondent bien & agrave; l'inclinaison de la ligne Gibraltar-Antioche sur les cartes modernes qui se rapprochent des projections de Ptol & eacute;m & eacute;e I et de Ptol & eacute;m & eacute;e II centr & eacute;es pr & egrave;s de Gibraltar, et leurs inclinaisons m & eacute;ridiennes pour les zones autour de G & ecirc;nes. On peut faire l'hypoth & egrave;se que, si les cartographes italiens de la fin du Moyen-Acirc;ge ont eu une collection de cartes ou de graphiques r & eacute;alis & eacute;s avant le moyen-& acirc;ge, il est th & eacute;oriquement possible qu'ils aient pu obtenir la g & eacute;om & eacute;trie typique des cartes portulans en composant graphiquement les copies manuscrites de ces cartes r & eacute;gionales grandes & eacute;chelles dans une projection de Mercator, ou de type Mercator, en utilisant une carte petite & eacute;chelle dans une projection conique ou pseudoconique (sur laquelle la convergence des m & eacute;ridiens est affich & eacute;e).

Anonymous Carte Pisane (c. 1275) and Cortona chart (c. 1300), as well as Pietro Vesconte's charts, made in 1311 and 1313, which represent some of the earliest known portolan charts, were cartometrically analysed to examine the geometric similarities between their coastal renderings. The research results show that not only the majority of their territorial coverage was drawn very similarly to each other but also that certain parts of the coastline are nearly identical between all the examined charts. Also, the magnitude and orientation of displacement vectors of residuals revealed that the Mediterranean and Black Sea areas on charts contain seven subsections which are on average, twice as accurate in comparison to the same area treated as a whole. The fundamental conclusion is that there is a high probability that the coastline renderings on the earliest known portolan charts are, actually, more or less skilfully made copies of the same source material used as a graphic template. The hypothetical source might have been an atlas whose origins date back to before the Middle Ages, containing charts whose extents were, perhaps, similar to the extents of detected subsections, which medieval cartographers were not able to assemble correctly due to their ignorance of map projections.

In the Pontifical Croatian College of St. Jerome in Rome, a manuscript geographic map of Illyricum is kept, drawn in 1663 by the architect and geographer, Pietro Andrea Buffalini of Rome. Cartographic analysis of this map has been carried out on several occasions, and the ecclesiastico-legal and historico-geographic context of its origin analysed. As contribution to previous research on the 1663 map of Illyricum, the depiction of the coast on that map is cartometrically compared with that on geographic maps and nautical charts from the late 16th century and the first half of the 17th. On the basis of these analyses it is confirmed that, with the 1663 map of Illyricum, a qualitative step forward was taken in depicting the northeast coast of the Adriatic. In addition, on the basis of research into available written data sources, it is concluded that Ivan Lučić made a key (co)authorial contribution to the shaping of the geographic content of this manuscript map.

The implementation of graticules on geographic maps and nautical charts, initially developed in the Hellenistic period, was a rediscovered novelty to Western European cartographers of the early modern period. The research sought to computationally examine the accuracy of spherical coordinates’ data extracted from selected geographical maps and nautical charts. Research results suggest that the cartographers who made geographic maps relied significantly on Claudius Ptolemy’s data on locations but managed to make certain accuracy improvements. The nautical charts with graticules showed significantly greater longitudinal accuracy, which suggests that they were created by using other data sources as their graphical templates; most likely the portolan charts that were already in existence at the time.

Cartographic representations of the Adriatic Sea basin on 11 (manuscript and printed) Early 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 and were subjected to the analysis of their spherical coordinates, which was conducted in parallel. The results show that cartographers who produced printed charts in 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.

The geometry of Adriatic Sea basin renderings on 12 portolan charts made from the late thirteenth to the late sixteenth century was compared to a modern map by applying Helmert transformation in order to preserve their initial geometry and by using the same 40 identical points per chart. In the first stage of the research, the geometry of the portolan charts was compared to six selected map projections in order to determine the geometrical ‘best fit'. In the second stage, networks of lines plotted on charts were divided regionally and functionally and compared to the ‘best fit’ map projection to determine their geometric patterns in more detail. 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.

The karst landscapes of the Mediterranean are regarded as some of the most vulnerable, fragile, and complex systems in the world. They hold a particularly interesting group of small islands with a distinctive, recognizable landscape. The Republic of Croatia (HR), which has one of the most indented coasts in the world, is particularly known for them. In this paper, we analyzed the spatio-temporal changes (STCs) in the landscape of Ošljak Island, the smallest inhabited island in HR. Landuse/landcover change (LUCC) analysis has been conducted from 1944 to 2021. The methodology included the acquisition of multi-temporal data, data harmonization, production of landuse/landcover (LU/LC) maps, selection of optimal environmental indicators (EIs), and simulation modeling. In total, eleven comparable LU/LC models have been produced, with moderate accuracy. STCs have been quantified using the nine EIs. The dominant processes that influenced the changes in the Ošljak landscape have been identified. The results have shown that, in recent decades, Ošljak has undergone a landscape transformation which was manifested through (a) pronounced expansion of Aleppo pine; (b) deagrarianization, which led to secondary succession; and (c) urban sprawl, which led to the transformation of the functional landscape. The most significant of the detected changes is the afforestation of the Aleppo pine. Namely, in a 77-year span, the Aleppo pine has expanded intensively to an area of 11.736 ha, created a simulation model for 2025, and pointed to the possibility of the continued expansion of Aleppo pine. Specific guidelines for the management of this new transformed landscape have been proposed. This research provides a user-friendly methodological framework that can efficiently monitor LUCCs of a smaller area in the case when geospatial data are scarce and satellite imagery of coarser resolution cannot be used. Moreover, it gives an insight into the availability and quality of multi-temporal data for the HR.

Distance and bearing navigational data for the Adriatic Sea basin, extracted from five late-medieval and Early Modern portolani, is examined and computationally compared to the geometry of their renderings, plotted both on a modern map projected in selected map projections, and on a sample of selected portolan charts georeferenced on them. The main conclusion is that the textual data on distances (expressed in portolan miles) and bearings (expressed in wind directions) contained in selected portolani do not, geometry-wise, represent the aggregated body of navigational measurements that were performed prior to their production, but that they were, most likely, extracted directly from portolan charts already in existence at the time. The secondary conclusion yielded by the methodology applied in the research is that the length of the portolan mile, which is still enigmatic to some extent, might be about 1.29 kms.

The research goal is to determine the level of accuracy of Adriatic Sea renderings on selected portolan charts by using the quantitatively–analytical approach and to determine the level of portolan charts usability for navigational purposes. The manuscript is divided into two main subject matters, each divided on three and four core chapters respectively. In the first subject matter, map projection that is geometrically most similar to the renderings of Adriatic Sea on portolan charts has been determined catrometrcally. Afterwards, chronological variations of mapping accuracy, along with geometrical deviations of particular charts from their average geometry, were determined compared to that projection. Also, in this part of the research, the Adriatic Sea basin was divided regionally and functionally, which resulted in detection of mapping accuracy variations for each particular segment of those divisions. In the second subject matter, the first aspect of charts’ usability are physical dimensions of Adriatic Sea renderings on charts themselves. The second aspect is the relation between portolan charts’ counterclockwise rendering tilt and direction and value of contemporary magnetic variation. The third aspect is the relation between terrestrial navigation across the Adriatic Sea and the portolan chart accuracy, whilst the fourth aspect represents geometrical interrelation between the accuracy of portolan charts and the accuracy of textual data on navigational routes contained in selected portolans. One of the fundamental conclusions is that the renderings of Adriatic Sea basin on portolan charts show immense accuracy levels, especially if bearing-mapping accuracy of cross-basin lines is considered, and that portolan charts, at least on their segments on which Adriatic Sea is being displayed, are intentionally made with the appliance of map projection which shows the characteristics of conformal cylindrical (Mercator) map projection in its normal aspect. Also, the research results implicitly suggest that it is highly unlikely that portolan charts are genuine medieval products, but rather that they represent the copies of older charts made in certain earlier period. Fundamental arguments that support such assumption are: calculated inexistence of charts’ accuracy increase during three-century period, higher accuracy of cross-basin bearings than that of coastal bearings, and higher accuracy of cross-basin routes in portolans (in general) than that of their coastal routes.