# Definition types and how to construct map projection full topic

A map projection is the conversion of the ellipsoidal figure of Earth into a planar surface. Basically, a map projection displays the locations of the features on a two-dimensional surface. It is done by plotting the
geographical coordinates from the 3D model of earth to the planar surface.

**Advantages of Map
Projection:**

Advantages of map projection are;

1.
It permits us to utilize two
dimensional maps.

2.
It permits the use of planar
coordinates in place of geographical coordinates.

**Limitations of Map
Projection:**

We cannot transform a 3D object
into 2D perfectly. Therefore, distortion will always be present in the map
projection. This is why we have lots of map projections. That is why certain
properties are always preserved whereas leftover is compromised.

**Types of Map
Projection:**

Map projections are generally
categorized by conserved property and the object used in map projection

**Classification on the
basis of preserved properties:**

Map projections are classified into
four general types according to maintained properties which are as follows;

**Conformal Projection:** This one maintains
local angles and forms.

**Equal area Projection:** this one shows exactly
size of areas.

**Equidistant projection**:
this one retains the consistency of scale along some lines.

**Azimuthal Projection**:
maintains some accurate directions.

The maintained property is
sometimes incorporated in the projection’s name. For example; Lambert Conformal
Conic Projection.

A projection may have several preserved
property except for conformal and equal area. Conformal and equal area properties
cannot be maintained in a single map projection.

The preserved property helps in the selection of projection. For example; an accurate impression of population
densities on the world map will be produced by choosing Equal area Projection.

**How to Construct a Map
Projection:**

The geometric object used in
projection to map the Earth on the planar surface is termed projection Surfaces.
Generally used objects are a cylinder, cone, and plane. For example, we can
create a map projection utilizing an object and a globe (ellipsoidal shape of the
World). This is done by putting the object tangent to the globe or the object
intersects the globe. Then a map projection is produced by locating the
geographical coordinates from the ellipsoidal shape of the World onto the cube.

**Classification on the
basis of projection surfaces:**

Hence,
we can construct a map projection by employing the three projection objects.
Thus, On the basis of projection objects, a map projection is divided into
three types. Which are as follows;

**Cylindrical projection:** Projection that is constructed using the cylinder
tangent to or intersecting the globe.

**Conic projection:** Projection produced by putting the cone tangent to
or intersecting the globe.

**Azimuthal Projection:** Projection created by putting the cone tangent to or
intersecting the globe.

Like
the preserved property, The name of the geometric object is also occasionally
included in its name. For example; Lambert Conformal Conic Projection.

**Case and Aspect:**

The
concept of case and aspect can be explained by the help of geometric objects. As
mentioned earlier, a map projection can be created by putting the geometric
object to the world model such that it is tangent to or intersects the globe.
When the geometric object is tangent to the globe, this is the simple case.
This results in one line of tangency for the other two projection surfaces
except for plane projection for which it results in a point of tangency. When an object intersects with the globe which is the secant case, it results in two lines
of tangency for conic and cylindrical projections. When the geometric object
used is a plane, it results in a line of tangency.

The position of a geometric object on the globe is described by the aspect. For example, a globe can have a plane at any point. The tangency at the pole is mentioned as a polar aspect while at the equator as an equatorial aspect. The tangency anywhere between the pole and the equator is stated as an oblique aspect.

**Map Projection Parameter:**

A map projection is based on some parameters in which few parameters are as follows;

1.
The first parameter is the lines
of tangency called **standard lines**. As
discussed above, the simple case has a single tangency line which means that in a simple case a map projection has only one standard line. Similarly, in the
second case, a map projection has two standard lines. If the line of tangency goes
along latitude. The standard line is called a standard parallel. Also, if it
follows a longitude/meridian it is called a standard meridian. Likewise, the
simple case has one standard parallel or meridian while the secant case has two
standard parallels or meridians.

2.
A map projection has no
distortion along the standard line. The tearing, shearing, and compression can
cause distortion if we move away from standard line or lines. The scale** **is a measure of distortion, and “It is the
ratio of the distance on the map to its corresponding ground distance”.

The
**principal scale, or the size of the reference globe**,
can accordingly be gotten from the proportion of the globe's radius to the
Earth's radius. The principal scale applies just to the line of tangency in a
map projection. That is why standard meridian and standard parallel are often
called longitude of the true scale and latitude of true scale respectively. The
local scale applies to the other parts of the map projection. The **scale factor** is the
standardized local scale, characterized as the proportion of the local scale to
the principal scale. The scale factor is 1 along the line of tangency and turns
out to be either under 1 or more than 1 away from the line of tangency.

3.
The other parameter of map
projection is the **central lines**. Central
lines are central parallel and central meridian. It represents the center of a
map projection. it is different from the standard lines which show the pattern
of distortion in a map projection. Likewise, the standard meridian and standard
parallel, central parallel, and central meridian are often called latitude of
origin and longitude of origin respectively.

The difference between the central lines and standard lines can be seen through the
transverse Mercator projection. it is defined by the central meridian and two
standard meridians. The scale factor at the standard meridians is one and is less
than one at the central meridian.

1.
The parameter of map projection
is the **false origin**. False origin is the
X and Y assigned coordinate values in other to avoid negative coordinates. When
a map projection is used as the basis of a coordinate system, central meridian
and central parallel become the origin of the coordinate system then the
system is divided into four quadrants. So, the locations on the map can have
negative coordinates depending on the quadrant in which the location lies. That is why false origin is used. Where X
assigned coordinate is called **false easting** and the Y coordinate is called **false northing**.

## Conclusion

We hope that you have learned about map projection. If you are facing any problem in solving school, college, or university assignments then you can write questions in the comment section below and we will provide you a solution to your assignment.

See Also: Full assignment of market equilibrium demand and supply graph consumer producer surplus

## No comments