Map Map ProjectionsProjections

Warm UpWarm Up

►Draw an accurate Draw an accurate map of South America map of South America with as many details with as many details as you can.as you can.

Warm UpWarm Up

►Discuss with your teammate and write Discuss with your teammate and write down down 5 examples5 examples to the following to the following questions:questions:

►What are some uses of What are some uses of mapsmaps??

► Imagine a globe made of glass. Overlay Imagine a globe made of glass. Overlay pieces of silver in the shape of the pieces of silver in the shape of the landmasses. Now imagine a light at the landmasses. Now imagine a light at the globe’s center, casting land-shaped globe’s center, casting land-shaped shadows in all directions. shadows in all directions.

► The cartographer’s job, roughly and The cartographer’s job, roughly and poetically, is to gather those shadows and poetically, is to gather those shadows and transform them into a reasonable portrait transform them into a reasonable portrait of the planet. of the planet.

► This first, crucial step in mapmaking is This first, crucial step in mapmaking is called the called the projectionprojection. Projections fall into . Projections fall into three basic categories: three basic categories: planar, , conic, and , and cylindrical. Picking the right projection is . Picking the right projection is crucial for achieving the map’s objective. crucial for achieving the map’s objective.

Planar (Flat-Plane) ProjectionPlanar (Flat-Plane) Projection

► Project the Earth onto a plane Project the Earth onto a plane that touches—or, technically, is that touches—or, technically, is tangent to—the globe at a tangent to—the globe at a single point, and you get a single point, and you get a planar projection. planar projection.

► Because this projection, also Because this projection, also known as an known as an azimuthalazimuthal projection, is most accurate at projection, is most accurate at its center, it is often used for its center, it is often used for maps focusing on one of the maps focusing on one of the Poles. Poles.

Conic ProjectionConic Projection

► Cap the globe with a cone to Cap the globe with a cone to achieve a conic projection. Cut achieve a conic projection. Cut open the cone, and the basis open the cone, and the basis of a map emerges. of a map emerges.

► The map will be least distorted The map will be least distorted along the line where the cone along the line where the cone touches the sphere. touches the sphere.

► Conic projections are handy Conic projections are handy for portraying the United for portraying the United States, which fits nicely within States, which fits nicely within the resulting smile-shaped the resulting smile-shaped map. map.

Cylindrical ProjectionCylindrical Projection

► Swaddle the globe and project Swaddle the globe and project its surface onto a cylinder. Slit its surface onto a cylinder. Slit the cylinder and flatten it into the cylinder and flatten it into a map. a map.

► This projection is most This projection is most accurate near the Equator and accurate near the Equator and greatly distorted near the greatly distorted near the Poles. Poles.

► The most famous cylindrical The most famous cylindrical map is the map is the MercatorMercator projection, projection, perfect for navigation but poor perfect for navigation but poor for teaching geography.for teaching geography.

Cylindrical Projection Cylindrical Projection

►Mercator MapMercator Map

PocketPocketGlobe?Globe?

Map DistortionMap Distortion

►Mapmakers tailor their creations to Mapmakers tailor their creations to focus on focus on area, , shapeshape, , distancedistance, , directiondirection, and other objectives. , and other objectives.

►National Geographic continually National Geographic continually refines the compromises involved in refines the compromises involved in crafting a crafting a world reference mapworld reference map. .

►Their objective chosen, cartographers Their objective chosen, cartographers rely on varied tools to accomplish it.rely on varied tools to accomplish it.

MAPS HAVE MAPS HAVE DISTORTION!DISTORTION!

!!Some parts aren’t accurate, because the world is Some parts aren’t accurate, because the world is

not flat.not flat.

AreaArea

► To compare geographical data To compare geographical data on a level playing field, pick a on a level playing field, pick a projection that maintains the projection that maintains the correct proportions among the correct proportions among the sizes of Earth’s landmasses. sizes of Earth’s landmasses.

► Such a map, often called an Such a map, often called an equal-area projection, would equal-area projection, would be useful to demographers. be useful to demographers.

► The price of getting the sizes The price of getting the sizes right, however, is right, however, is distortion in distortion in the shapes of the continentsthe shapes of the continents. .

ShapeShape

►Preserving the shape of a Preserving the shape of a landmass—an important landmass—an important concern for those wanting to concern for those wanting to see what Earth “really” looks see what Earth “really” looks like—gets harder as the area like—gets harder as the area covered gets larger. covered gets larger.

►A world map can only preserve A world map can only preserve the continents’ shapes by the continents’ shapes by distorting their sizesdistorting their sizes. Maps . Maps that stress shape are called that stress shape are called conformal. conformal.

DistanceDistance

► Geometry students the world Geometry students the world over learn that the shortest over learn that the shortest distance between two points distance between two points is a line. Not on most maps. is a line. Not on most maps.

► If distance is the focus of your If distance is the focus of your map, choose a projection map, choose a projection centered on a key point. Lines centered on a key point. Lines radiating from the middle will radiating from the middle will be equidistant. be equidistant.

► Shapes and sizes will be Shapes and sizes will be distorteddistorted, however, especially , however, especially at the outer edges. at the outer edges.

DirectionDirection

►Many navigational charts rely Many navigational charts rely on projections focused on on projections focused on direction. Such maps, usually direction. Such maps, usually centered on one place, allow centered on one place, allow mariners to plot a journey mariners to plot a journey they can actually sail without they can actually sail without constant course corrections. constant course corrections.

► That ability matters far more That ability matters far more at sea than at sea than shapes and sizes, shapes and sizes, which can get distortedwhich can get distorted. .

Putting It All TogetherPutting It All Together

► National Geographic has wrestled for National Geographic has wrestled for decades with the choice of a decades with the choice of a projection for reference maps of the projection for reference maps of the world. In 1922 the Society adopted world. In 1922 the Society adopted the Van der Grinten projection, which the Van der Grinten projection, which encloses the world in a circle. encloses the world in a circle.

► Their cartographers switched in 1988 Their cartographers switched in 1988 to the to the RobinsonRobinson projection, on which projection, on which the high latitudes are less distorted in the high latitudes are less distorted in size (but more so in shape). A decade size (but more so in shape). A decade later, the Society began using the later, the Society began using the Winkel Tripel projection, which Winkel Tripel projection, which provides a better balance between provides a better balance between size and shape size and shape

Robinson ProjectionsRobinson Projections

►a compromise map projection showing a compromise map projection showing the poles as lines rather than points the poles as lines rather than points and more accurately portraying high and more accurately portraying high latitude lands and water to land ratio latitude lands and water to land ratio

InterruptionsInterruptions

►Only globes are edgeless. Only globes are edgeless. All other maps have to stop somewhere. All other maps have to stop somewhere.

Those unavoidable interruptions can Those unavoidable interruptions can actually help focus the map by drawing the actually help focus the map by drawing the reader’s eye toward—or away from—reader’s eye toward—or away from—particular features. The projection seen particular features. The projection seen here clearly focuses on land and would be here clearly focuses on land and would be helpful for mapping terrestrial data such as helpful for mapping terrestrial data such as human population. Yet it distorts the sea, human population. Yet it distorts the sea, which covers 70 percent of the planet. which covers 70 percent of the planet.

The West Wing – Peters The West Wing – Peters ProjectionProjection

The West Wing – Peters The West Wing – Peters ProjectionProjection