What type of map exaggerates distances at the poles

The homolosine projection is also useless for navigation, as the lines of longitude point in different directions over various parts of the map. The Robinson planisphere projection Figure 2. There is still some distortion, but not as much as in a Mercator.

This projection is used mostly for data presentation. Other map types include bathymetric maps Figure 2. These are similar to topographic maps for terrestrial locations, with lines connecting areas of equal depth. The closer together the lines, the steeper the feature.

In the example below, the steep continental slope is represented by the high density of depth contours as the colors transition from light blue to dark blue. The result is that Europe although also Africa is in the centre of the conventional world map — a rather colonial perspective. The familiar meridian-centred map conveniently places the map edges down the middle of the Pacific Ocean so no continent is chopped in two.

But maps centred on the Pacific Ocean also work well because the edges of the map conveniently run down the middle of the Atlantic. This places east Asia in a more prominent position and pushes Europe to the edge.

Much of Oceania and Asia uses Pacific-centred maps. American-centred maps are also in use, but these have the unfortunate consequence of partitioning Asia to either side of the map. Our meridian-centred view of the world shapes how we refer to world regions. Seeing Europe on the left of a map and the Americas on the right can seem counter-intuitive, but it is just as correct as any other arbitrary chop point.

The world is, after all, round. An alternative is to place the North Pole in the centre. It is strangely disorienting to gaze on the world from a polar perspective.

The lower hemisphere should be hidden from view by the curve of the Earth because you can only see half a sphere at a time. But on the azimuthal polar projection from the north, the southern hemisphere has been pulled into view on the page, with the consequence that Antarctica centrifuges into a doughnut around the edge of the circular map. This highlights the disadvantage of the projection as it distorts both the area and shape of landmasses, but distances from the North Pole are accurate in all directions, with those further from the centre becoming more enlarged on their east-west axis.

Choice of a scale factor influences indirectly the distance between the secant lines. This way we can balance distortion within the area of interest. Remember the Orange-Video in Figure 6. Geometric distortions while mapping spherical surfaces are inevitable.

Different projections are characterised by the fact that they can preserve some geometrical properties at the expense of other geometric properties. For example, if relative size of regions on the Earth is preserved everywhere on a map, their shapes will be deformed to a lesser or greater extent. Compromises have to be made between the preserving properties.

This becomes more important with the increasing distance from a point or line of tangency, i. Equidistant - preserves distances. A distance measured on a map and multiplied by the scale factor results in the true distance in nature. Usually this property is preserved only along tangent or secant lines or in a specific direction.

Equal area — preserves size of a region. A measurement of a size of a region area on a map corresponds to the size of that region in reality considering the respective scale. Conformal — preserves angles locally.

A specific, local angle on a map is consistent with the respective, local angle on the Earth's surface. This property leads to local! True direction — preserves global directions. A specific direction on a map at any point should correspond to the actual direction in which the point is located. In many cases this task is not so easy. Look at the following brainteaser in Figure 6. What is the distance between A and D? Generally, it is impossible to create a map that has true-to-scale distances in all directions and between all points.

We therefore speak of partially equidistant projections. This, however, holds for a single point, i. For this reason, this projection must be specifically tailored for each point from which you want to measure spherical distances. The projection shown in Figure 6. Equidistant azimuthal projections can represent not only a hemisphere , but the entire world. However, the shape-related distortions increase rapidly towards the edges. The constant latitude intervals make it clear that the length of the meridians in this situation remains the same.

In addition to the equidistant property, this projection also preserves direction but only in its origin, i. Due to this property, all great circles passing through the origin are represented by the projection as straight lines. The property of true direction is particularly important for navigation purposes.

This projection is used in a wide range of applications like navigation, radio relay, and also in the representation of polar regions. A popular example for azimuthal equidistant projections is the logo of the UN as shown in Figure 6. The projection of the map extends to 60 degrees south of latitude, and includes five concentric circles.

The equidistant cylindrical projection equidistant cylindrical, cylindrical equirectangular, plane chart only has true distance along the equator and the meridians figure below. For distance measurements with an east or west component, the scale increases rapidly when moving from the equator towards the poles. The maximum deviation in horizontal distances can be seen at the poles, which are shown on the map as lines with the length of the equator.

An equidistant cylindrical projection with the line of tangency at the equator and with the origin at 0. The degrees of latitude and longitude are presented as if they were Cartesian coordinates. This simple planar representation of spherical coordinates is used in most GISystems as standard representation of unprojected spatial data. A rocket that is launched from Salzburg, Austria heads east and needs to fly in a straight line around the world.

Before you continue reading, think about the countries it would cross in its flight-path? If you thought the rocket flies over China and the U. A, you are mistaken. In reality, the rocket crosses the equator near Sumatra, flies over Australia, enters the northern hemisphere near Colombia and finally returns to Salzburg. At each point of this path, the rocket is exactly east or west of the starting point Salzburg, Austria.

This is because the true east direction is determined by following the great circle that intersects the reference meridian at a right angle. Now, a completely different situation arises if the rocket uses a compass to find east and steers itself in the direction pointed by the compass. Although the rocket is now flying due east, it no longer refers to its starting point Austria. Instead, it uses the last meridian it flew over as a reference to find which direction is east. From Austria, it would seem that the rocket constantly changes its direction according to the direction pointed by the compass.

In case 1 the rocket flies along a great circle and in case 2 , it moves along a rhumb line see Lesson on Coordinate Systems to refresh your memory on a rhumb line. In case 1 the cardinal direction in which the rocket is located to the starting point is constant. The course angle changes constantly but with respect to north. The situation is exactly the opposite in case 2: the course changes continuously in the direction of movement by always steering slightly to the left and, therefore, the cardinal direction in which it is located also changes with respect to the starting point.

However the respective course angle - angle between last reference meridian crossed and the east direction pointed by the compass - with respect to the north remains constant. In practice, the kind of application determines which of the two cases is needed. For example, true direction is important in the field of transmitting radio waves or for some military applications like long range unguided missiles.

The second case is required to navigate with a compass from A to B. Consequently a design of a grid will differ accordingly in order to meet various requirements: to determine the cardinal direction in which a particular point lies, you need a projection that has true direction i.

However, in order to determine the course angle which is to be followed to reach a destination, you need a conformal projection in which rhumb lines become straight lines.

Equal area projections preserve the relative size of regions on the entire map and they have property of equivalence. Due to demands of equivalence, the scale factor can only be the same along one or two lines or from maximum two points. Scale factors and angles around all other points will be deformed; it is therefore impossible to have a projection that is equal area and conformal at the same time.

Secant case provides a more even distribution of distortion throughout the map. Features appear smaller between secant lines scale 1. The aspect of the map projection refers to the orientation of the developable surface relative to the reference globe.

The graticule layout is affected by the choice of the aspect. The meridians are vertical and equally spaced; the parallels of latitude are horizontal straight lines parallel to the equator with their spacing increasing toward the poles. Therefore the distortion increases towards the poles. Meridians and parallels are perpendicular to each other. The meridian that lies along the projection center is called the central meridian. In conical or conic projections , the reference spherical surface is projected onto a cone placed over the globe.

The cone is cut lengthwise and unwrapped to form a flat map. For the polar or normal aspect , the cone is tangent along a parallel of latitude or is secant at two parallels. These parallels are called standard parallels. Distortion increases by moving away from standard parallels. Features appear smaller between secant parallels and appear larger outside these parallels. Secant projections lead to less overall map distortion. The polar aspect is the normal aspect of the conic projection.

The cone can be situated over the North or South Pole. The polar conic projections are most suitable for maps of mid-latitude temperate zones regions with an east-west orientation such as the United States.

Oblique aspect has an orientation between transverse and polar aspects. Transverse and oblique aspects are seldom used. In planar also known as azimuthal or zenithal projections, the reference spherical surface is projected onto a plane. The plane in planar projections may be tangent to the globe at a single point or may be secant.

In the secant case the plane intersects the globe along a small circle forming a standard parallel which has true scale. The normal polar aspect yields parallels as concentric circles, and meridians projecting as straight lines from the center of the map. The distortion is minimal around the point of tangency in the tangent case, and close to the standard parallel in the secant case.

The polar aspect is the normal aspect of the planar projection. The plane is tangent to North or South Pole at a single point or is secant along a parallel of latitude standard parallel. The polar aspect yields parallels of latitude as concentric circles around the center of the map, and meridians projecting as straight lines from this center.

Azimuthal projections are used often for mapping Polar Regions, the polar aspect of these projections are also referred to as polar azimuthal projections.

In transverse aspect of planar projections, the plane is oriented perpendicular to the equatorial plane. And for the oblique aspect, the plane surface has an orientation between polar and transverse aspects. These projections are named azimuthal due to the fact that they preserve direction property from the center point of the projection.

Great circles passing through the center point are drawn as straight lines. Some classic azimuthal projections are perspective projections and can be produced geometrically. They can be visualized as projection of points on the sphere to the plane by shining rays of light from a light source or point of perspective.

Three projections, namely gnomonic, stereographic and orthographic can be defined based on the location of the perspective point or the light source. The point of perspective or the light source is located at the center of the globe in gnomonic projections.