What Does Planisphere Mean
We explain what a planisphere is, its types, characteristics and various examples. Also, what is a celestial planisphere.
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 earth ‘s surface with the distribution of continents , the characteristics of the different regions and oceans .
The name “world map” refers to a planisphere whose plane is designed to adapt to a sphere or globe shape, in order to achieve a three-dimensional representation of the Earth . Planispheres are frequently used in academic and scientific fields as they provide accurate information and allow the study of both the earth’s surface and the stars and constellations in the sky through the celestial planisphere. The discipline that studies maps is called cartography 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.
See also: Earth globe
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 relief (such as valleys , mountains and other geographical features), the vegetated regions, the bodies of water and the main rivers.
- Of political division. They are maps that indicate, by means of different types of lines, the limits and divisions of each country or State and their respective capitals. They also designate rivers, lakes and seas with their limits according to the corresponding state.
Other types of maps for specialized use are:
- The geographical physical map. It contains information on land elevations, hydrography, and oceans.
- The geological map. Contains information on springs, rocks, ground faults , volcanoes, and areas with mineral presence (such as gold, silver, and copper ).
- The climate map. It contains information on the different climatic groups in each region .
- The topographic map. It contains information on landforms, both natural and artificial, through contour lines, colors and symbols.
- The urban map. It contains information on urban areas and routes of communication .
Characteristics of a planisphere
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 symbols. 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 that of 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.
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 in 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 meet 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
Continue with: Meridians and parallels