Cartographic Projections

Cartographic projections are those mathematical transformations that allow to represent and project a spherical shape in a plane, and convert the geographical coordinates, which are latitude and longitude, into Cartesian coordinates (x, y). These coordinates arise from the need to be able to capture the earth’s surface on a flat surface with as little deformation as possible.

In addition, cartographic projections can be divided according to their metric quality (Conform, Equidistant and Equivalent), their projective qualities (Perspectives, Planar, Stereographic, Orthographic and Transverse), according to their development (Conical and Cylindrical) and according to their projections (Sinusoidal and Goode).

Types of Cartographic Projections most used today

Many of the most common map projections are classified according to the surface of the projection used: Conical, Cylindrical or Planar.

We have then:

• The Conic (Tangent):

An imaginary cone is placed on the globe. The cone and globe touch along a line of latitude. This line is the standard parallel. The cone is cut along the line of longitude opposite the central meridian and becomes a plane.

• The Conical (Secant):

An imaginary cone is placed on the globe that crosses part of its surface. The cone and globe touch along two lines of latitude. These lines are the standard parallels. The cone is cut along the line of longitude opposite the central meridian and becomes a plane.

• Cylindrical orientations:

An imaginary cylinder is placed around the globe. The cylinder can touch the globe along a line of latitude (normal type), along a line of longitude (transverse type), or along any other line (oblique type).

• Planar orientations:

An imaginary plane is placed on the globe. The plane can touch the globe at one of its poles (polar type), at the equator (equatorial type) or on any other line (oblique type).

• The polar orientation perspectives:

Planar or azimuth projections can be reproduced with different perspectives. The gnomonic projection point is located in the center of the globe. In stereographic projection, the contact point is located at the opposite pole of the globe. The perspective point in orthographic projection is located at infinity.

Official Cartographic Projections

The EPSG and its importance:

The EPSG is the acronym for European Petroleum Survey Group, it is an oil organization in Europe.

Likewise, it is formed by specialists in geodesy, topography and cartography applied to the area of exploitation and development of a repository of geodetic parameters that contains information on ancient and modern systems or reference frames, cartographic projections and ellipsoids from around the world.

• In Peru, the Universal Transverse Mercator (UTM) cartographic projection is currently used, where we locate the 17s zone (EPSG: 32717), 18s zone (EPSG: 32718) and 19s zone (EPSG: 32719).
• In Chile, the Universal Transverse Mercator (UTM) projection is used, zone 18 (EPSG: 32718) and zone 19 (EPSG: 32719).
• In Mexico, there are 6 UTM zones: zone 11 (EPSG: 4484), zone 12 (EPSG: 4485), zone 13 (EPSG: 4486), zone 14 (EPSG: 4487), zone 15 (EPSG: 4488) and zone 16 (EPSG: 4489).
• In the United States, the most frequently used datums are North American Datum 1927 (NAD 1927), North American Datum 1983 (NAD 1983), and World Geodetic Survey 1984 (WGS 1984).
• In Spain, the ETRS89 system (European Terrestrial Reference System 1989) as the official geodetic reference system for geographic and cartographic reference in the area of the Iberian Peninsula and the Balearic Islands. In the case of the Canary Islands, the REGCAN95 system is adopted.
• In Australia, GDA2020 (EPSG 7856), is the new coordinate system, to facilitate a more robust, accurate and capable datum, more aligned with global positioning systems.

Importance of Cartographic Projections

If the cartographic projection did not exist, maps could not be made and geographic information systems could not be developed. Cartographic projections are essential for cartography, since they allow a mathematical transformation that converts the spherical coordinates of the earth’s surface into flat coordinates, thus being able to represent three-dimensional objects on a flat surface.

References

• Suárez Peña, E. (2017). Cartographic projections and maps.

https://repositorio.unican.es/xmlui/handle/10902/12594

• Martinez, C. (2016). Cartographic projections, overseas competition and colonial experience in Terra Brasilis: the case of France in the 16th century. History School Magazine, 15(1), 00-00.

https://digital.csic.es/handle/10261/23344