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Map Projections

All you need to know

If you are primarily interested in buying a map for decor purposes then the main thing to know is that a map projection determines the shape of the map. For example item # 4101-1_01 is a map of the whole world using our NASA: MODIS GEBCO Land & Bathy 500m imagery in a Plate Carre projection (also known as a Geographic projection). Item # 4102_02 is also a map of the whole world from the same imagery but it is in a Hotine Oblique Mercator projection. When searching our online map catalog you can choose to reduce your search results to include only maps in a particular map projection by searching the catalog by type, see left side of this page.

Plate Carre or Geographic Projection

(Above) Projection: Geographic (Plate Carre)

(Right) Projection: Hotine Oblique Mercator

Hotine Oblique Mercator Projection

Brief explanation

For purposes of explaining projections further we will consider the world to be sphere (it is in fact not a perfect sphere but rather a spheroid) and maps are flat. A map projection is a means of “projecting” the spherical map of the world, or part of it, on to a flat surface. It is impossible to do this without introducing distortion, sometimes very significant distortion. Consider trying to wrap cellophane around an orange without a wrinkle. Some distortions of conformality, distance, direction, scale and area always result. On very large scale maps (i.e. maps covering small areas) many of these distortions are imperceptible to the eye and therefore insignificant. On the other hand, they are completely obvious on small scale maps like maps of the whole world.

Practical examples

If you planned on sailing from Lisbon to the Havana you would probably need to know the distance and the direction. If you drew a straight line from one to the other, on most maps it would NOT be the shortest route. You could choose an Azimuthal Equidistant projection centered on one of those two locations. Distances and direction to any point from the projection center would be correct. Unfortunately, no map projection can show true distance between any pair of points on a map. On the other hand a Gnomonic projection is the only map where the shortest route from any point to any other point is a straight line, however distances along those lines are not shown correctly. Unfortunately, if you were to set sail you would need to know that in order to follow that shortest path your compass bearing would need to change constantly throughout that journey. If that seems too difficult and if your concern is just to make sure you arrive at the destination you may prefer to sail with your compass set on a fixed bearing. To find this bearing you would need to use a Mercator projection. In such a map the direction of a line drawn from Lisbon to Havana would be that compass bearing and it would show the exact path that you would take if you held that bearing. This would not be the shortest route. The problem with many of these projections is that other distortions arise. In a Mercator projection Greenland appears the same size as Africa where in fact Africa is almost 14 times larger than Greenland. Even the very familiar Geographic projection results in similar though less distortion. If displaying areas correctly is important then an equal-area map projection is used, such as the Mollweide projection.

Interesting applications

At Newport Geographic we try to make our maps useful and educational but above all we want them to be interesting. To that end we have developed some completely unique maps. Consider our PolyView map series, for example item # 41BH-1-2_04 . It is made up of 32 separate polygons (20 hexagons and 12 pentagons) that together represent the whole world. Each polygon is a separate map in Gnomonic projection. A straight line between any two points that stays on a polygon is a great circle and so represents the shortest distance between those two points. Any such line that crosses polygons but remains within the map will approximate a great circle. Since the area covered by each polygon is relatively small distortion across the entire map is minimal. The result is a flat map that can give the shortest route between two points with very little error in distance, scale and area.