7 junio, 2024

Planisphere: what it is, characteristics, types, examples

What is a planisphere?

A planisphere It is a map that represents the entire surface of the Earth in a plane, that is, in two dimensions (length and width). They are also known by the name of mapamundi (world map).

The first planispheres were prepared in the 16th century, based on the geographical information collected in the great exploration voyages of Christopher Columbus, Ferdinand Magellan and Vasco de Gama.

Although these primitive planispheres are very inaccurate if we compare them with today’s ones, they were a great help for navigation until the 18th century, when technology advanced enough to create more accurate maps.

There are also celestial planispheres. These serve to indicate the position in the sky of the stars and constellations seen from a certain place on the planet and on a specific date.

Characteristics of the planispheres

Planispheres are characterized by:

Be flat or two-dimensional.
Represent the earth’s surface or the position of various celestial bodies.
Have different scales.
Present parallels and meridians, which are used to write the exact coordinates of any point on the planisphere.
Reflect information of different types: geological, political, fluvial, economic, etc.
Be an effective tool to condense information and communicate it.

Types of planispheres

Planispheres are classified according to the information they reflect and whether they represent the Earth or the celestial bodies visible to the naked eye from its surface.

terrestrial planisphere

It represents the entire earth’s surface: the five continents, the oceans, Antarctica, etc. Terrestrial planispheres can reflect information of various types.

For example, we can make a terrestrial planisphere in which only the rivers are indicated, or only the highest mountains. We can make another with the temperatures, coloring the hottest areas of the planet red and the coldest ones blue.

Another planisphere might report altitude, with the highest places on the planet colored a darker shade than those closer to the sea.

political planisphere

It is a widely used type of terrestrial map in which only geopolitical information is reflected.

That is to say: the names of the countries and their territories delimited through lines. City names and locations are also often included.

Political maps can reflect historical information: for example, how the world was organized in 1980, when Russia and numerous countries around it still formed a single state (the Soviet Union).

It can also represent migratory information, indicating with arrows the points of origin, the route and the destination of the flows of people at a given historical moment.

celestial planisphere

It is also a flat map, but it represents the relative location of the stars and constellations visible from Earth.

We speak of relative location because celestial bodies appear at different points in the sky depending on the time of year and the place in the world from which they are viewed.

Celestial planispheres are useful for identifying lights seen in the night sky. Currently there are portable planispheres that show the location of the celestial bodies according to the date that the user selects.

Components of a planisphere

In order for the image and information reflected in a planisphere to be properly understood and used, it is necessary to include the following elements.

Qualification

It is placed at the upper or lower end of the planisphere, in the center. The title clearly indicates what information the world map offers. For example «World map of groundwater», «Map of migratory flows», «Map of marine currents» or «Map of tectonic plates».

coordinates

Parallels, meridians and height must also be indicated on the planisphere.

the parallels They are imaginary lines that divide the earth’s surface in a north-south direction. The equator is the parallel that divides the Earth into the northern and southern hemispheres.
the meridians they are also imaginary lines that divide the earth in an east-west direction. The Greenwich meridian or 0 meridian divides the planet into the eastern and western hemispheres. Using the parallels and meridians we can determine the coordinates, which indicate the exact position of a point on the planisphere.
The height, on the other hand, refers to the vertical distance that exists between a certain point on the planisphere and sea level. This is indicated by means of a scale.

Cardinal points

In the planispheres the four cardinal points must be indicated: north, south, east and west. In some cases they are indicated with the capital letter of each cardinal point placed where it corresponds: north at the top; the south at the bottom; west to the left and east to the right.

In other planispheres, the cardinal points are indicated by the wind rose, an ancient symbol in the form of a circle in which the directions in which the circumference of the horizon is divided are marked.

scales

We have them of three types: the numerical scale and the graphic scale.

Numerical scale: It is a mathematical relation between the size of the planisphere and the real size of the Earth.

For example, if the numerical scale of a planisphere is 1:100,000, this means that the world map is 100,000 times smaller than the area it represents, that is, the entire earth’s surface. Or put inversely: the real Earth is 100,000 times bigger than the map that represents it.

A world map or planisphere with a scale of 1:50,000 will be twice as large, while a third map with a scale of 1:200,000 will be two times smaller than the first.

Graphic scale: allows us to know the real distance that exists between two points on the planisphere. Suppose we have a map whose graphic scale is 1 centimeter = 100 kilometers. This means that each centimeter of the map is equivalent to 1000 kilometers in the actual size of the planet.

If I want to know the real distance between two cities that are separated on the map by 3.6 centimeters, I just have to multiply 3.6 x 1000. The real distance between these two cities is 3600 kilometers.

References

(2022). Compass Rose. Britannica School. Taken from escola.britannica.com.br.
(s/f). How to Use a Planisphere. Taken from astronomy.sierracollege.edu.
(s/f). Importance of the Planisphere. Taken from importance.org.
Caraballo Folgado, Alba. (2021). World map for elementary school children. Taken from guiainfantil.com.

Deja una respuesta

Tu dirección de correo electrónico no será publicada. Los campos obligatorios están marcados con *