We explain what a planisphere is, its types and characteristics. Also, what is a celestial planisphere?
What is a planisphere?
A planisphere is a representation of the Earth’s sphere on a two-dimensional plane. It is a scale map that reproduces the Earth’s surface with the distribution of the continents and oceans.
Planispheres are frequently used in academic, school, and scientific settings, as they provide accurate information and allow for practical and detailed study of the Earth’s surface. You must read about Greenwich Meridian once.
Unlike a globe, which shows a three-dimensional representation of the Earth, the two-dimensional nature of the planisphere requires the use of a cartographic projection; that is, it requires the use of mathematical calculations to represent the spherical surface of the planet on a plane.
In all cases, image distortion is inevitable. This is because it is not possible to faithfully represent a spherical surface on a plane without some type of deformation occurring.
Planispheres are a reflection of the time and era in which they were created. For example, planispheres prior to the 15th century did not include the American continent because European cartographers were unaware of its existence. Maybe you should definitely read about Numbering System once.
Characteristics of a Planisphere
The main characteristics of planispheres are:
- They represent the Earth’s surface on a two-dimensional plane.
- They are usually physical, political, or physical-political.
- They are used in academic and school settings.
- They are used to represent phenomena and processes on a planetary scale.
- They require a cartographic projection to convert the Earth’s three-dimensionality to the map’s two-dimensionality.
- There are celestial planispheres, which show the stars and constellations.
Types of Planispheres
The types of planispheres are:
- Physical: These are maps that show, through variations in color, the different types of relief (such as plains, mountains, and plateaus), oceans, seas, and major rivers.
- Political: These are maps that indicate, through different types of lines and colors, the boundaries and divisions of each country or state, and their respective capitals and major cities.
- Physical-Political: These are the most common maps. They show both physical and political elements through symbols, signs, and colors.
Parts of a Planisphere
The parts that make up all types of planispheres and that accompany the map image are:
- Title: Indicates the content or type of planisphere.
- Compass Rose: Indicates the cardinal points (north, south, east, west).
- Scale: Indicates the number of times the map is reduced from the actual size of the Earth. It is used to calculate distances.
- References: Indicates the meaning of the colors, symbols, and signs that appear on the planisphere.
In addition to the continents and oceans, planispheres show latitude and longitude with imaginary lines (parallels and meridians), which are used to locate places geographically.
Regarding parallels, the following are marked: the equator, the Tropics of Cancer and Capricorn, and the Arctic and Antarctic circles. Regarding meridians, the Greenwich Meridian and the Greenwich Antimeridian, or Daylight Line, are also marked.
Thematic Planispheres
Planispheres can be used to mark various global phenomena, processes, or events, whether historical or current. For example:
- Trade flows.
- Migratory flows.
- Expansion of empires and colonial possessions.
- Economic blocs.
- Socioeconomic indicators.
In all cases, the complete image of the Earth’s surface provides a comprehensive view of the mapped phenomena, which facilitates the analysis and interpretation of the processes depicted.
History of the planisphere
The first flat maps are believed to have been created by the Babylonians around 600 BC. They showed a limited view of the world, based on observations and what was known about the planet at that time.
In contrast, during the Middle Ages, maps represented a theocentric view of the world, centered on Jerusalem. These types of maps, called T-in-O maps, showed a flat Earth divided into three parts by T-shaped waterways, all surrounded by a circular ocean. The best-known of these maps is the Discarion of Hereford Cathedral in England. Its unique feature is that it contains religious ornamentation based on the Bible.
With the Renaissance and the expansion of European exploration, planispheres became more precise and incorporated information about newly discovered territories.
Today, digital cartography makes it possible to produce planispheres with highly accurate and detailed information about the Earth’s surface.
The Celestial Planisphere
A celestial planisphere is a star chart represented on a plane that, when observing the night sky, helps locate stars and constellations.
This type of planisphere is usually made up of two discs: a larger one for the constellations and a smaller one for the stars. These discs are joined in the center on an axis that allows the smaller disc to rotate to identify features on a given day and month.
The creation of these maps also involves the use of cartographic projections that adapt the celestial sphere to a plane, similar to how the Earth’s surface is projected on a planisphere.
References
All the information we offer is supported by authoritative and up-to-date bibliographic sources, which ensure reliable content in line with our editorial principles.
- Garmendia, C. (2020). Cartographic projections: what should I know?. Idecor. idecor.gob.ar
- Lifeder. (n.d.). Planisferio. lifeder.com/planisferio
- Medellín Planetarium. (n.d.). Prometheus: Celestial Chart, a Map to Follow the Sky. planetariomedellin.org
