The map projections are a systematic transformation of the longitudes and latitudes of a position on the surface of the sphere. Map projections are important in creating maps with map projections that distort the surface in some way. Some of the distortions on the maps are acceptable while other distortions are not acceptable depending on the purpose of the map. The projection of the map is classified according to the type of projection surface on which the globe is projected conceptually. There are several cartographic projections that preserve some properties of the sphere at the expense of others.
Types of cartographic projections
A cylindrical projection is any projection in which the meridians are mapped on parallel vertical lines and the latitudes are mapped on horizontal lines. The projections extend from east to west according to their geometric constructions and are the same in any chosen latitude. Cylindrical projections are distinguished from each other by stretching from north to south indicated by φ. Stretching from north to south is equivalent to east to west but grows with faster latitude than east-west extending in the case of central cylindrical projection. The Mercator projection is an example of a cylindrical projection that became a standard cartographic projection due to its ability to represent constant course lines. Mercator distorts the dimensions of geographic objects because its linear scale increases with the increase in latitude. The distortion caused by the Mercator distorts the perception of the entire planet by exaggerating the areas located far from the equator.
The pseudocylindrical projections present the meridian as a straight line while others parallel like sinusoidal curves that are longer than the central meridian. The scaling of the pseudocylindrical projections are straight along the central meridian and also along the parallels. On a pseudocylindrical map, the points farthest from the equator have higher latitudes than other points, preserving the north-south relationship. The pseudocylindrical projections include sinusoidal with the same horizontal and vertical scales. The Robinson projection was created to promptly show the globe as a flat image. The projection is neither of equal area nor conform due to the compromise to show the whole planet.
Van der Grinten Projection
Van der Grinten is a compromised projection that is neither equal nor compliant. It is an arbitrary scale projection of the plane that projects the entire earth in a circle. The Van der Grinten projection preserves the image of the Mercator projection and reduces its distortion. However, the polar regions can still be distorted by the Van der Grinten projection.
The conical projections have meridians mapped on equidistant parallels that start from the top while the parallels are mapped on circular arcs that are centered at the top. Two standard lines displayed as secant lines are collected in the process of creating a conical projection. When a single parallel line has used the distance along the parallels it is lengthened. Examples of conic maps include equidistant conics, of Albers and Lambert.
Pseudoconical projections are projections with parallels that are circular arcs with common central points. Unlike conical projections, the meridian is not bound to be a straight line. Examples of pseudoconical projections include “bonne”, which is a projection of maps of equal area. The maps are not bound to rectangles or disks. Pseudoconic projection is one of the oldest types of maps and although they were used by Ptolemy, they are rarely seen today.
Distortion of distortions on map projections
Projections of the map without distortion would represent the correct distance, direction, shapes and areas on a map. However, cartographic projections have distortions that depend largely on the size of the area being mapped. Scale distortions on maps are shown on the map by a distortion ellipse or by using a scale factor which is the ratio of the scale at a given point to the real scale. Distortions on the maps of countries or cities are not obvious to the view and can be identified only when distances and areas are calculated.
What are the different types of map projections?
|degree||Map Projection Name||Examples|
|1||cylindrical||Mercator, Cassini, Equirectangular|
|2||Pseudocylindrical||Mollweide, Sinusoidal, Robinson|
|3||conical||Conical in accordance with Lambert, conical by Albers|
|4||Pseudoconical||Bonne, Bottomley, Werner, American Polyconic|
|5||azimuthal||Gnomonica, Lambert azimuthal equal area, stereographic|
|6||polyhedral||Authagraph, octane projection, Cahill butterfly map|
|7||Other||GS50, Peirce quuncuncial, Van der Grinten|