What is a map projections?

A map projection is one of many methods used to represent the 3-dimensional surface of the earth or other round body on a 2-dimensional plane in cartography (mapmaking). This process is typically, but not necessarily, a mathematical procedure (some methods are graphically based).

The ways in which we visualize the world are varied- we have pictures, maps, globes, satellite imagery, hand drawn creations and more. What kinds of things can we learn from the way we see the world around us? For centuries mankind has been making maps of the world around them, from their immediate area to the greater world as they understood it at the time. These maps depict everything from hunting grounds to religious beliefs and speculations of the broader, unexplored world around them. Maps have been made of the local waterways, trade routes, and the stars to help navigators on land and sea make their way to different locations. How we visualize the world not only has practical implications, but can also help shape our perspectives of the Earth we live in.

There are many kinds of maps made from a variety of materials and on a variety of topics. Clay tablets, papyrus, and bricks made way for modern maps portrayed on globes and on paper; more recent technological advances allow for satellite imagery and computerized models of the Earth. Certain map projections, or ways of displaying the Earth in the most accurate ways by scale, are more well-known and used than other kinds. Three of these common types of map projections are cylindrical, conic, and azimuthal.

Cylindrical Map Projections

Cylindrical map projections are one way of portraying the Earth. This kind of map projection has straight coordinate lines with horizontal parallels crossing meridians at right angles. All meridians are equally spaced and the scale is consistent along each parallel. Cylindrical map projections are rectangles, but are called cylindrical because they can be rolled up and their edges mapped in a tube, or cylinder. The only factor that distinguishes different cylindrical map projections from one another is the scale used when spacing the parallel lines on the map.

The downsides of cylindrical map projections are that they are severely distorted at the poles. While the areas near the Equator are the most likely to be accurate compared to the actual Earth, the parallels and meridians being straight lines don’t allow for the curvature of the Earth to be taken into consideration. Cylindrical map projections are great for comparing latitudes to each other and are useful for teaching and visualizing the world as a whole, but really aren’t the most accurate way of visualizing how the world really looks in its entirety.

Types of cylindrical map projections you may know include the popular Mercator projection, Cassini, Gauss-Kruger, Miller, Behrmann, Hobo-Dyer, and Gall-Peters.

THE MERCATOR MAP PROJECTION IS ONE OF THE MOST WELL KNOWN CYLINDRICAL MAP PROJECTIONS.

Conic Map Projections

Secondly, conic map projections include the equidistant conic projection, the Lambert conformal conic, and Albers conic. These maps are defined by the cone constant, which dictates the angular distance between meridians. These meridians are equidistant and straight lines which converge in locations along the projection regardless of if there’s a pole or not. Like the cylindrical projection, conic map projections have parallels that cross the meridians at right angles with a constant measure of distortion throughout. Conic map projections are designed to be able to be wrapped around a cone on top of a sphere (globe), but aren’t supposed to be geometrically accurate.

Conic map projections are best suited for use as regional or hemispheric maps, but rarely for a complete world map. The distortion in a conic map makes it inappropriate for use as a visual of the entire Earth but does make it great for use visualizing temperate regions, weather maps, climate projections, and more.

THE ALBERS PROJECTION IS AN EXAMPLE OF A CONIC MAP PROJECTION.

Azimuthal Map Projection

The azimuthal map projection is angular- given three points on a map (A, B, and C) the azimuth from Point B to Point C dictates the angle someone would have to look or travel in order to get to A. These angular relationships are more commonly known as great circle arcs or geodesic arcs. The main features of azimuthal map projections are straight meridian lines, radiating out from a central point, parallels that are circular around the central point, and equidistant parallel spacing. Light paths in three different categories (orthographic, stereographic, and gnomonic) can also be used. Azimuthal maps are beneficial for finding direction from any point on the Earth using the central point as a reference.

LAMBERT AZIMUTHAL EQUAL-AREA PROJECTION.

Map projection types all have their pros and cons, but they are incredibly versatile. Even though it is nearly impossible to create an entirely accurate map projection there are uses for even the most imperfect depictions of the Earth. Map projections are created for certain purposes and should be used for those purposes. In the end each and every map projection has a place, and there is no limit to the amount of projections that can be created.

Interactive Map Projection

www.jasondavies.com. A cool site in playing around with different map projections and transitions.

Source:

www.geolounge.com,

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