From the portolan chart of the mediterranean to the latitude chart of the atlantic

Research output: ThesisDoctoral Thesis


In this thesis a methodology for the systematic geometric analysis and modeling of pre-Mercator nautical charts is proposed and tested, aiming at contributing to better understand their geometric properties and methods of construction. The suggested approach involves the application of a series of cartometric techniques: georeferencing, on the basis of a sample of control points of known geographic coordinates; the interpolation of the geographical graticules implicit to the representations; the assessment of scales of distance and latitude; the assessment of the navigational accuracy, by comparing the latitudes, directions and distances measured on the charts with the corresponding exact values, affected by magnetic declination; and the identification of the routes underlying the charts’ construction. A numerical model was developed using the concept of ‘multimensional scaling’, here generalized to distances and directions measured on a spherical Earth, to simulate the main geometric features of the charts. To estimate the spatial distribution of the magnetic declination in various times two sources were used: the historical observations made by D. João de Castro in 1538 and 1541, and a recent geomagnetic model.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • NOVA Information Management School (NOVA IMS)
  • Painho, Marco, Supervisor
  • Contente Domingues, Francisco, Supervisor, External person
Award date21 Sept 2010
Publication statusPublished - 21 Sept 2010


  • Geometric
  • Analysis
  • Methods
  • Construction
  • Cartometric
  • Geomagnetic model


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