Week 6 Lab- map projections

Map projections display the spherical earth on a two dimensional plane.  Transferring this data can be difficult, as some information will be lost in the process.  Different methods of map projection can yield differing data.  Different projections will keep certain aspects of the spherical data accurate, such as distance or area.  Depending on the intended use, certain map projections will be appropriate for differing situations.  For example, an ocean going vessel would not want to use an equal area projection, as this angles, direction and distance; possibly misleading the ship and its crew into a perilous situation.  Conformal maps would be most appropriate for navigation purposes (except in air travel, when an equidistant map should be used) as they preserve angles and local directions.

Equidistant maps could be used to calculate the total distance traveled by the aforementioned ship.  This would be best accomplished with a two point equidistant map, as opposed to an azimuthal projection, which bases its scale from a single point.  My examples of equidistant maps are both azimuthal.  The first centers on the North Pole, while the second centers on the coordinate origin, or where the equator and prime meridian intersect. 

Equal area maps are what they sound like; maps which preserve the correct ratio of land area.  These are useful for displaying data such as land use, or population density where the data is more about spatial distribution then exact distances or angles.  Distance can vary greatly between various equal area projections, as exemplified by my two equal area maps here shown.  The first is a Lambert Cylindrical projection, and shows the distance between Washington DC and Kabul, Afghanistan as being 10,108 miles.  The second is a Lambert Azimuthal equal area projection, which centers on the North Pole.  The Azimuthal projection however, shows the distance between Washington D.C. and Kabul, Afghanistan as being only 6,806 miles.  That is a 3,300 mile difference, which is more than the distance from San Francisco to New York City. 

My Mercator maps are conformal.  They could be used in my ship example for navigation and plotting purposes, as they preserve angles and represent constant navigations lines and allow the captain to stay the course.  I had trouble finding difference between the various Mercator projections, as all the ones I tried seemed to render similar or identical maps.