The earth has a spherical shape, more precisely, it is slightly flattened at the edges at the points that are its poles. But this is not particularly noticeable on a planetary scale, because it is accepted that the Earth is a ball, and its surface is taken as spherical.
The marking of the Earth by meridians and parallels made it possible to accurately determine the coordinates of any object that moves (plane, thunderclouds), or which occupies a specific place on the planet (city, island). This has given quite a few advantages to any objects moving in space. Previously, people were guided by the stars, by the position of the sun in the sky. It was not as accurate as using modern technology, although if you suddenly find yourself on a desert island without the means that are so familiar in our lives — smartphones, tablets, laptops, respectively, without access to the Internet, without a navigator and other things, then It would not be superfluous to know the very “inconvenient” methods of calculating coordinates.
You can use a navigation system in which the necessary coordinates will be entered, and autopilot devices will be able to move themselves where necessary without a person. But first things first. Consider the main points and circles on the globe.
Some historical information
Questions about the coordinates concerned the minds of people for a long time, even before our era. Prominent scientists in the path of developing a coordinate system were Hipparchus and Ptolemy. These people lived in the second or first centuries BC, but, nevertheless, they could determine the coordinates of stars with separating accuracy . These were the great people of their era, powerful geographers and astronomers. It was they who introduced the concept, which we now call the coordinate system, and from their work it is already becoming clear what geographical coordinates are. At that time, these people did not know that the Earth revolves around the Sun. Hipparchus suggested that the surface of our planet can be considered an ideal sphere, and on its example, he explained various foundations regarding spherical geometry.
Globe - the most accurate model of the Earth
It is with the help of the globe that you can easily determine the coordinates of any country, island or other object. With its help, it is easiest to show what are the meridians and parallels, geographic poles, other points and lines of the Earth.
By the way, the first globe was created a long time ago, before our era, and it was made by a certain Kratet of Mullsky in 150 BC, at the same time when Hipparchus and Ptolemy lived. Of course, the globe cannot demonstrate all the small details, but in general it allows you to perfectly describe the general picture of what our planet is, and perfectly demonstrates, for example, what points of the earth are called geographical poles,
On the globe, it’s easy to see where any country, sea, ocean, location of the continents or even their relief is located. It depends on what will be depicted by the creator of a particular globe. It can be purely political, only with the division of continents into countries and indicating large objects such as oceans. Most likely, it will be a small decorative globe. Training copies contain much more information about the geographic poles and geographic location of any part of the world.
In general, three parameters are distinguished by which they characterize the Earth in a geographic coordinate plan. Therefore, we consider the main points, lines and planes on the surface of the Earth.
What is the axis of the earth
If we take the Earth for a ball, then it becomes clear that it has a line that serves as a stereometric figure. What exactly is it about? This is a line that is a diameter, rotating around which a semicircle creates a whole sphere. What diameter in comparison with the Earth is called an axis. This is an imaginary line, which is not really there, but there is a daily rotation around it, and it is considered that it passes through the North and South poles.
Poles of the planet Earth
What points of the earth are called geographic poles? They are the well-known cold deserted north and south poles. In stereometry, what is called the “geographical pole” is the point at which the earth’s rotation axis (diagonal of a spherical body) intersects with the sphere. The last in this case is the surface of the Earth.
Through these two poles pass all the meridians, which we will discuss below.
What are parallels?
We continue to consider the Earth as a sphere and determine what the parallels are in this case. If we assume that the planet, like the ball, has a center, then the axis of the Earth will pass through it and will be divided into two equal parts, like the diameter of the radii.
If you draw a certain plane that will be perpendicular to the axis, then it will intersect the sphere in a certain circle, that is, the Earth along a line called a parallel. The parallel with the largest diameter passes through the center of the globe of the Earth, which is a large circle and is called the equator. It divides the sphere into two equal hemispheres. All similar circles that are created by planes perpendicular to the axis are also called parallels, but they are small circles compared to the equator. And the lines passing through the geographic poles will be called meridians. By the way, it is thanks to the equator that our Earth is divided into two parts - northern and southern. Accordingly, there are geographical poles of planet Earth, which are named depending on which part of the world they are located.
Meridian
If we draw a large plane through the axis itself and through the poles, we get a circle, which is called the "full meridian". All meridians are the same in length, as they pass through a straight line and two points on it in different planes. Only their location changes.
The system of meridians and parallels, which are depicted on the map and on the globe, is a degree network.
It is two-dimensional, since it is specified by only two coordinates - the parallel coordinate and the latitude coordinate. That is, what are geographic coordinates? These are two numbers, indicators of latitude and longitude. Such numbers have a dimension in degrees and minutes.
At the beginning of the article it was said that the Earth is not quite a sphere, that it is a bit flattened. What is this expressed in? The equator is 40075.7 kilometers long, while the meridian is 40008.5 kilometers long. The poles are a little closer to the equator, although on a global scale this is not very noticeable.
Earth spheroid planes
It is those imaginary planes that run parallel or perpendicular to the earth's axis, are the main ones. The area of the plane that passes through the meridian is called, respectively, the plane of the earth’s meridian. The most prominent of them is the Greenwich Meridian. It divides the land into the eastern and western hemispheres. The main plane that passes through the equator and divides the earth into two parts is the Northern and Southern Hemispheres.
Origin lines
All coordinates are calculated using conventional stereometry. The reference points, more precisely, the meridian of reference and the parallel of reference, from which the coordinates of any place on Earth are calculated, are selected. The one that passes through London, namely through the Greenwich Observatory, was chosen as the zero meridian. As the line, which is considered the origin of geographical latitude, it is customary to take the longest meridian - the equator.
An interesting fact about the Greenwich Meridian. There is a system for assigning coordinates to a point, and it is called World Geodetic System-84, or WGS-84 for short, (84 is the year the system was adopted), which the whole world uses, and in which the ERS Reference Meridian, passing near Greenwich, is the zero meridian, just 5.31 arc minutes east.
What lines of the earth give width and longitude
Children at school often confuse these concepts - meridians and parallels, which of them is width and what is longitude. So, the equator is the origin of geographical latitude, then when the Greenwich meridian is the starting line for calculating longitude.
Geographic latitude can range from 0 to 90 degrees. Depending on which side of the equator the point is located, it is assigned the value of north latitude or south. So, for example, New York has a latitude of 40 degrees 43 minutes north latitude, and Sydney has 33 degrees 52 minutes south latitude. It is written as follows: 40 about 43 ', 33 about 52'.
Similarly with geographic longitude. It can also be calculated using degrees and minutes, just that longitude has a range of values from 0 to 180 degrees. It can be western if it goes west from the prime meridian, and east (similarly, east from the prime meridian).
As previously indicated, the prime meridian passes through Greenwich and has a value of 0 degrees. And what points of the Earth are called the geographical poles of the planet and what are their coordinates? These are points that are ninety degrees latitude and zero degrees longitude.
To summarize
On planet Earth, as well as on the sphere, there are basic points, lines and planes. What points of the earth are called geographical poles, we have already figured out. These are the points through which the axis of the Earth's daily rotation passes . If a plane passes through this axis and crosses geographic poles, then it forms intersections of the Earth’s sphere, which are called meridians.
There is a zero meridian passing in London, and several others that have dimensions up to 180 degrees (there may be at least 180). If a certain plane passes through the axis of rotation of the Earth, namely perpendicular to it, then their intersection with the sphere of the Earth is a parallel. The parallel that has the longitude is called the equator. It is he who is the starting point for the latitude coordinate. All coordinates are measured in degrees and smaller fractions - minutes, seconds. There are sixty minutes in one degree, and sixty seconds in one minute. Two bars are used to indicate seconds (such as those for minutes).