A brief introduction to map projections By Mark VanderVen vanderm6@cc A brief introduction to map projections By Mark VanderVen  vanderm6@cc.wwu.edu

We’ll define it as the study, science, history, and art of map-making. Cartography No simple, easy definition We’ll define it as the study, science, history, and art of map-making. 

Cartography Comprised of many techniques and methods. Includes measuring the earth's shape, distances, and features Collect and store information about terrain, places and people Create and design processes for graphical representation of data Print and publish spatial information. Adapt three-dimensional features to flat models

A spherical surface (or section of) cannot be transformed to a planar (flat) surface without incurring some distortion

Projection “A mathematical development of one surface onto another. In the cartographic context, one surface is the earth and the other is a flat surface such as a map. The mathematics usually convert from the spherical coordinates of latitude and longitude to a Cartesian coordinate system. The projection is one element of a coordinate system definition.” Norm's GIS Glossary http://www.mentorsoftwareinc.com/resource/glossary.htm

Second Defintion A map projection is a systematic transformation of the latitudes and longitudes of locations from the surface of a sphere or an ellipsoid into locations on a plane. Maps cannot be created without map projections. All map projections necessarily distort the surface in some fashion. https://www.revolvy.com/main/index.php?s=Orthographic%20projection%20in%20cartography

…more simply put… A map projection is a flat map surface representing all or part of a spherical surface (Earth).

REMINDER A spherical surface (or section of) cannot be transformed to a planar (flat) surface without incurring some distortion

Map properties that can be distorted Shape Area Distance Direction

Distance ?

Area

Shape?

Direction?

For a web page on coordinate systems see: http://www.colorado.edu/geography/gcraft/notes/coordsys/coordsys.html

Comparisons ESRI “No Projection” (Lat/Long) Mercator

Conclusions Different projections are used to preserve Shape Area Distance Direction No projection can do all simultaneously.

For More What on Earth are Map Projections Prof. Alan Saalfeld Geography Ohio State University Click Here for pdf