Cartographic Projections Cartographic Projections Paolo Zatelli Alfonso Vitti Dept. Civil and Environmental Engineering University of Trento Paolo Zatelli University of Trento 1 / 18
Cartographic Projections Outline 1 Cartographic projection 2 Cartographic projection used in Italy Paolo Zatelli University of Trento 2 / 18
Cartographic Projections Cartographic projection Cartographic systems To create a map it is necessary to choose: the reference system and the associated ellipsoid (Datum) a set of coordinates and measures that realize the adopted reference system the cartographic projection and the related parameters Paolo Zatelli University of Trento 3 / 18
Cartographic Projections Cartographic projection Cartographic systems To give cartographic coordinates a meaning we have to label numbers with information about: the datum the cartographic projection While datum and the cartographic projection are distinct and different datum/projection combinations are possible, it is common to provide simply the cartographic projection leaving the Datum implied. For example, the UTM projection is used both with the global reference system WGS84 and with the ED50. Paolo Zatelli University of Trento 4 / 18
Cartographic Projections Cartographic projection Proiezioni cartografiche Cartographic projections transport coordinates from an ellipsoid to a cartographic plane. The two surfaces are not equivalent from a topological viewpoint, i.e., it is not possible to transport from one surface to the other without deformations. It is possible: to preserve angles (conformal maps) to preserve surfaces (equivalent maps) to minimize the deformation, without having none of them actually null (compromise maps) Paolo Zatelli University of Trento 5 / 18
Cartographic projection used in Italy The more common projections used in Italy are: UTM (Universal Trasversal Mercator) Gauss-Boaga, official Italian national projection Cassini-Soldner, used for the Nuovo Catasto dei Terreni italiano (new Italian Cadaster) Paolo Zatelli University of Trento 6 / 18
UTM Projection It is a Gauss map so: it is conformal along the central meridian, the scale factor is constant meridians and parallels are perpendicular it is symmetrical wrt the equator Paolo Zatelli University of Trento 7 / 18
UTM Projection The projection can be depicted as the projection of the ellipsoid to an horizontal cylinder (tangent to a meridian) Paolo Zatelli University of Trento 8 / 18
UTM Projection Since deformations increase moving away from the tangential meridian: the projection is performed using 6 wide zones the central meridian has a scale factor of 0.9996 the East coordinate of the central meridian is set to 500000 m the projection is bounded in the latitude range [ 80 ; +80 ] Paolo Zatelli University of Trento 9 / 18
UTM Projection UTM zones Paolo Zatelli University of Trento 10 / 18
UTM Projection The Italy falls in zones 32 and 33. A small part is in the zone 34 Paolo Zatelli University of Trento 11 / 18
UTM Projection This projection is used: in the official Italian cartography in ED50 to express the coordinates of a GPS survey, usually labeled simply as WGS84 (should be UTM-WGS84) Paolo Zatelli University of Trento 12 / 18
Gauss-Boaga projection I It is a Gauss projection: there are only two zones ( fusi in Italian) of 6 30, Ovest and Est that correspond to the UTM zones 32 and 33 the central meridian has a scale factor of 0.9996 the East coordinate of the first meridian is set to 1500000 m whereas the East coordinate of the second meridian is set to 2520000 m Paolo Zatelli University of Trento 13 / 18
Gauss-Boaga projection II Paolo Zatelli University of Trento 14 / 18
Double parametrization - IGM 1:25000 Paolo Zatelli University of Trento 15 / 18
Double parametrization - CTP PAT Paolo Zatelli University of Trento 16 / 18
Cartographic Projections Appendice Bibliografia Bibliografia Benciolini B., 2004, Dispensa sui sistemi di riferimento, comunicazione personale. Monti C., 1984, Elementi di cartografia con riferimenti alla situazione cartografica in Italia, in Spazi verdi territoriali. Corso post-laurea di formazione professionale - Milano, 1983, pp. 92-142, Franco Angeli editore, Milano, 1984. Paolo Zatelli University of Trento 17 / 18
Cartographic Projections Appendice Licenza Questa presentazione è c 2009 Paolo Zatelli, disponibile come Paolo Zatelli University of Trento 18 / 18