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 adoptedreference systemthe 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 datumthe cartographic projection
While datum and the cartographic projection are distinct and differentdatum/projection combinations are possible, it is common to providesimply the cartographic projection leaving the Datum implied.
For example, the UTM projection is used both with the global referencesystem 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 acartographic plane.
The two surfaces are not equivalent from a topological viewpoint, i.e., itis not possible to “transport” from one surface to the other withoutdeformations.
It is possible:
to preserve angles (conformal maps)to preserve surfaces (equivalent maps)to minimize the deformation, without having none of them actuallynull (compromise maps)
Paolo Zatelli | University of Trento | 5 / 18
Cartographic Projections | Cartographic projection used in Italy
Cartographic projection used in Italy
The more common projections used in Italy are:
UTM (Universal Trasversal Mercator)Gauss-Boaga, official Italian national projectionCassini-Soldner, used for the Nuovo Catasto dei Terreni italiano(new Italian Cadaster)
Paolo Zatelli | University of Trento | 6 / 18
Cartographic Projections | Cartographic projection used in Italy
UTM Projection
It is a Gauss map so:
it is conformalalong the central meridian, the scale factor is constantmeridians and parallels are perpendicularit is symmetrical wrt the equator
Paolo Zatelli | University of Trento | 7 / 18
Cartographic Projections | Cartographic projection used in Italy
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
Cartographic Projections | Cartographic projection used in Italy
UTM Projection
Since deformations increase moving away from the tangentialmeridian:
the projection is performed using 6◦ wide zonesthe central meridian has a scale factor of 0.9996the East coordinate of the central meridian is set to 500000 mthe projection is bounded in the latitude range [−80◦; +80◦]
Paolo Zatelli | University of Trento | 9 / 18
Cartographic Projections | Cartographic projection used in Italy
UTM Projection
UTM zones
Paolo Zatelli | University of Trento | 10 / 18
Cartographic Projections | Cartographic projection used in Italy
UTM ProjectionThe Italy falls in zones 32 and 33. A small part is in the zone 34
Paolo Zatelli | University of Trento | 11 / 18
Cartographic Projections | Cartographic projection used in Italy
UTM Projection
This projection is used:
in the official Italian cartography in ED50to express the coordinates of a GPS survey, usually labeledsimply as WGS84 (should be UTM-WGS84)
Paolo Zatelli | University of Trento | 12 / 18
Cartographic Projections | Cartographic projection used in Italy
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 mwhereas the East coordinate of the second meridian is set to2520000 m
Paolo Zatelli | University of Trento | 13 / 18
Cartographic Projections | Cartographic projection used in Italy
Gauss-Boaga projection II
Paolo Zatelli | University of Trento | 14 / 18
Cartographic Projections | Cartographic projection used in Italy
Double parametrization - IGM 1:25000
Paolo Zatelli | University of Trento | 15 / 18
Cartographic Projections | Cartographic projection used in Italy
Double parametrization - CTP PAT
Paolo Zatelli | University of Trento | 16 / 18
Cartographic Projections | Appendice | Bibliografia
Bibliografia
Benciolini B., 2004, Dispensa sui sistemi di riferimento, comunicazionepersonale.
Monti C., 1984, Elementi di cartografia con riferimenti alla situazionecartografica in Italia, in “Spazi verdi territoriali. Corso post-laurea diformazione professionale - Milano, 1983”, pp. 92-142, Franco Angelieditore, 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