planisphere

Geographic

2022

We explain what a planisphere is, its types, characteristics and various examples. Also, what is a celestial planisphere.

There are different types of planispheres depending on the type of information they show.

What is a planisphere?

A planisphere is a representation of the terrestrial sphere, in a two-dimensional plane. Is a Map to scale that reproduces the land surface with the distribution of continents, the characteristics of the different regions and the oceans.

The name "world map" refers to a planisphere whose plane is designed to adapt to a shape of a sphere or globe, in order to achieve a three-dimensional representation of the world. Earth.

Planispheres are often used in academic and scientific fields as they bridle information precise and allow the study of both the earth's surface and the stars and the constellations in the sky across the celestial planisphere.

The discipline that studies maps is called mapping and is responsible for collecting information on the composition of the surface. There are different types of planispheres depending on the type of information they show, the most common ones are physical and political.

Terrestrial planisphere

The most common types of planispheres are:

  • Of physical division. They are maps that show, through variations in the intensity of the colors, The different types of reliefs (What valleys, moutains and other geographical features), vegetated regions, masses of Water and the main rivers.
  • Of political division. They are maps that indicate, by means of different types of lines, the limits and the divisions of each country or Condition and their respective capitals. They also designate rivers, lakes and seas with its limits according to the corresponding state.

Other types of maps for specialized use are:

  • The geographical physical map. Contains information on terrain elevations, hydrography and oceans.
  • The geological map. Contains information on springs, rocks, faults of the I usually, volcanoes and areas with the presence of minerals (such as gold, silver and copper).
  • The climate map. It contains information on the different climatic groups of each region.
  • The topographic map. It contains information on landforms, both natural and artificial, through contour lines, colors and symbols.
  • The urban map. Contains information on urban areas and roads communication.

Characteristics of a planisphere

The compass rose indicates the cardinal points.

The common characteristics in all types of planispheres are the title that indicates the content, the compass rose (that indicates the Cardinal points), the design made to scale, the geographical coordinates, the legends with references and symbology.

Also, all planispheres have parallels (horizontal lines) and meridians (vertical lines) are traces that are drawn on the map to imaginatively divide the planet into circles.

The main parallel is the equator, a line perpendicular to the Earth's axis that divides it into two hemispheres: the North and the South. The main meridian is Greenwich divides the Earth into two hemispheres: the East and the West.

Geographic coordinates are measured in degrees and allow locating the position of any point on the earth's surface. They are measured with two variables:

  • The latitude. It is the distance between a point on the earth's surface and the equator line to which a latitude of zero degrees (0º) corresponds. The value increases as the parallel lines move away from the equator towards the poles, dividing into north latitude or south latitude as appropriate. All the points that are found on the same line of parallel will have the same latitude value.
  • The length. It is the distance between a point on the earth's surface and the Greenwich meridian which corresponds to a longitude of zero degrees (0º). The value increases as the meridians move away from the Greenwich line, dividing into east or west longitude. All the points that are on the same meridian line will have the same longitude value.

Celestial planisphere

A fixed celestial planisphere can only show the sky at one time of the year.

A celestial planisphere is a star chart represented in a plane that, when observing the night sky, helps to locate the stars and constellations at a certain time of the year (that is, according to the location of the planet at a time of its orbital path).

This type of planisphere is made up of two discs (a larger one for constellations and a smaller one for stars) that come together in the center on the same axis that allows the smallest disc to rotate.

The celestial planisphere contains the compass rose with the cardinal points, so it is necessary to point the north position to the respective real North. Then, the disk must be rotated to select the corresponding hour, day and month to identify where the main stars and constellations are.

Planispheres with names

A political planisphere marks the boundaries between countries. A physical planisphere marks the different heights of the terrain with a color code. A planisphere can also show the tectonic plates that make up the lithosphere.

In 1746 Johann Baptist Homann developed this planisphere. Educational planispheres can provide summary information on flora and fauna.
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