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Understanding Map Projections. Which one is correct?. Albers Equal Area. Mercator. The essential question. How do you represent all or part of an ellipsoid object on a flat piece of paper?. Planar Projections. If the earth was transparent, You could stick a sheet of paper in it and
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Which one is correct? Albers Equal Area Mercator
The essential question • How do you represent all or part of an ellipsoid object on a flat piece of paper?
Planar Projections • If the earth was transparent, • You could stick a sheet of paper in it and • Shine a light through it • The picture on the paper would create a map.
Other ways to project the map • On to a cone of paper • On to a cylinder of paper.
Projection Results • Any type of map projection will result in some distortion of the area being mapped. • Each of the projections have strengths and weaknesses.
Mercator Projection • Distances are true only along Equator, but are reasonably correct within 15° of Equator; • Areas and shapes of large areas are distorted. Distortion increases away from Equator and is extreme in polar regions.
Conic Projections • Earth's surface is projected onto a tangent or secant cone, which is then cut from apex to base and laid flat.
References • http://geology.isu.edu/geostac/Field_Exercise/topomaps/map_proj.htm • http://en.wikipedia.org/wiki/Sphere#Topology • http://egsc.usgs.gov/isb/pubs/MapProjections/projections.html • http://www.nationalatlas.gov/articles/mapping/a_projections.html