When is a map projection made

This is your imaginary Earth. But when you peel the orange, flatten and stretch it out, you can begin to see everything. Similarly, a map projection is a method by which cartographers translate a sphere or globe into a two-dimensional representation. In other words, a map projection systematically renders a 3D ellipsoid or spheroid of Earth to a 2D map surface. There are multiple ways to represent a sphere on a two-dimensional surface… Like Jason Davies popular Map Projection Transition Visualizer.

For example, map projections distort distance, direction, scale, and area. Every projection has strengths and weaknesses. All in all, it is up to the cartographer to determine what projection is most favorable for its purpose.

When you place a cone on the Earth and unwrap it, this results in a conic projection. Both of these map projections are well-suited for mapping long east-west regions because distortion is constant along common parallels. But they struggle at projecting the whole planet.

While the area is distorted, the scale is mostly preserved. For conic map projections , distance at the bottom of the image suffers with the most distortion. When you place a cylinder around a globe and unravel it, you get the cylindrical projection. Strangely enough, you see cylindrical map projections like the Mercator and Miller for wall maps even though it inflates the Arctic.

You can place it in a vertical, horizontal or oblique position such as the State Plane Coordinate System. Each one has its own use in mapping the world.

These types of projections plot the surface of Earth using a flat plane. It is most commonly used over Polar areas, but can be used for small scale maps of continents such as Australia. The great attraction of the projection is that the Earth appears as if viewed form space or a globe. This is a conformal projection in that shapes are well preserved over the map, although extreme distortions do occur towards the edge of the map. One interesting feature of the Stereographic projection is that any straight line which runs through the centre point is a Great Circle.

The advantage of this is that for a place of interest e. Canberra, the capital city of Australia a map which uses the Stereographic projection and is centred on that place of interest true distances can be calculated to other places of interest e. His mathematics was considered revolutionary for its time and is still considered important today. Today the Lambert Conformal Conic projection has become a standard projection for mapping large areas small scale in the mid-latitudes — such as USA, Europe and Australia.

It has also become particularly popular with aeronautical charts such as the , scale World Aeronautical Charts map series. This projection commonly used two Standard Parallels lines of latitudes which are unevenly spaced concentric circles. The projection is conformal in that shapes are well preserved for a considerable extent near to the Standard Parallels.

For world maps the shapes are extremely distorted away from Standard Parallels. Distances are only true along the Standard Parallels. Across the whole map directions are generally true. One of the most famous map projections is the Mercator, created by a Flemish cartographer and geographer, Geradus Mercator in It became the standard map projection for nautical purposes because of its ability to represent lines of constant true direction. Constant true direction means that the straight line connecting any two points on the map is the same direction that a compass would show.

In an era of sailing ships and navigation based on direction only, this was a vitally important feature of this projection.

Its construction is such that the lines of longitude and latitude are at right angles to each other — this means that a world map is always a rectangle. Also, the lines of longitude are evenly spaced apart.

But the distance between the lines of latitude increase away from the Equator. This projection uses a cylinder to touch a globe at the equator plane and cast the light for meridians and parallels to appear on cylindrical surface. Meridians are straight lines and equally spaced, while parallels are also straight lines but their spacing increases as they get closer to the poles. Shapes are represented more accurately in tangent point areas. However, the closer to the poles, the more distortion occurs.

Therefore, it is not typically used to make a map in areas above 80 degrees north latitude and below 80 degrees south latitude. The Mercator projection is being applied in varying patterns, such as by taking a cylinder to touch a globe with the axis of cylinder intersecting that of the globe at the right angle, leaving the cylinder to touch any single meridian. By that way, a central Meridian is created. When the cylinder is unrolled, the area adjacent to the central meridian will have constant scales.

This type of projection is commonly used to display different parts of the Earth. It maintains area around the central meridian. The equator is a straight horizontal line intersecting the central meridian at a right angle. Other meridians are curved lines, while other parallels are straight lines. This map projection was initiated by Karl B. Mollweide in However, there is more scale accuracy in the equatorial regions. The projection is ideal for making global maps.

All the parallels are straight lines perpendicular to a central meridian, while other lines are curved like those in the Mollweide projection. The values of sine curves are used to create meridians, making the meridian spacing wider than that of the Mollweide projection.

The Sinusoidal projection is typically used for map making of the equatorial regions such as in South America and Africa. This type of equal-area projection is a combination of the Homolographic and the Sinusoidal. Normally, the Sinusoidal projection is applied between the 40 degrees south and 40 degrees north latitudes, grafted to the Homolographic in the areas out of the above mentioned range. Azimuthal equal-area projection: distance from the tangent point on the map is equal to straight-line distance through the earth.

Azimuthal orthographic projection maps each point on the earth to the closest point on the plane. Conformal map projections preserve angles. Stereographic projection touches a plane to the earth and projects each point in a straight line from the antipode of the tangent.

Gall-Peters projection wraps a cylinder around the earth and maps each point on the earth to the nearest point on the cylinder. Cordiform projection designates a pole and a meridian; distances from the pole are preserved, as are distances from the meridian which is straight along the parallels. What is GIS? What is a Map Projection? Creation of a Map Projection The creation of a map projection involves three steps in which information is lost in each step: selection of a model for the shape of the earth or round body choosing between a sphere or ellipsoid transform geographic coordinates longitude and latitude to plane coordinates eastings and northings.

The metric properties or a map are area shape direction distance scale Choosing a projection surface If a surface can be transformed onto another surface without stretching, tearing, or shrinking, then the surface is said to be an applicable surface. Using globes vs. Choosing a model for the shape of the Earth The projection is also affected by how the shape of the earth is approximated. Categories Projection classification is based on type of projection surface that is used.