Publicação
From the portolan chart of the mediterranean to the latitude chart of the atlantic
| Resumo: | 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. |
|---|---|
| Autores principais: | Gaspar, Joaquim Filipe Figueiredo Alves |
| Assunto: | Geometric Analysis Methods Construction Cartometric Geomagnetic model |
| Ano: | 2010 |
| País: | Portugal |
| Tipo de documento: | tese de doutoramento |
| Tipo de acesso: | acesso a metadados |
| Instituição associada: | Universidade Nova de Lisboa |
| Idioma: | inglês |
| Origem: | Repositório Institucional da UNL |
| Resumo: | 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. |
|---|