Geographic coordinates are numbers that indicate the position of an arbitrary point on or near the surface of the Earth. These numbers are called longitude and latitude.

The geographic coordinate system is defined in relation to some major points and lines on the surface of the globe. Two of these points are the Earth's poles. The geographical poles of the Earth are the points at which the axis of rotation of the Earth intersects the surface of the globe. That of the two poles, when observed from which the rotation of the Earth occurs counterclockwise, is called the North. The opposite pole is called the South Pole.

The plane passing through the center of the Earth perpendicular to the axis of rotation is called the plane of the Earth's equator. The circle along which this plane intersects the surface of the Earth is called the equator. The equator divides the globe into two equal hemispheres: Northern and Southern.

The plane passing through an arbitrary point M of the earth's surface and the axis of rotation of the Earth intersects the earth's surface along a line called the meridian of the point M. Together, the meridians form a system of imaginary lines connecting the North and South geographic poles. The position of each meridian is determined in relation to one or another meridian, taken as the initial one. The prime meridian and the equator are the main lines by which the geographic coordinate system is set.

At different times, different meridians were taken as the initial ones. From 1634 it was carried out through the island of Ferro. This tiny island is considered the westernmost point of the Old World, and thus the initial meridian symbolically divided the countries of the Old and New Worlds into two hemispheres.

Since 1884, by decision of the International Meridian Conference, it was agreed to consider the initial meridian that passes through one of the oldest astronomical observatories in the world - the Greenwich Observatory, which at that time was located on the outskirts of London.

The dihedral angle between the planes of the initial meridian and the meridian of a given point on the earth's surface is one of the geographic coordinates - longitude. Geographic longitude can be measured either east (east longitude) or west (west longitude) of the prime meridian.

To distinguish points lying on the same meridian from each other, a second geographical coordinate is introduced - latitude. Latitude is the angle that a vertical line drawn at a given place on the Earth's surface forms with the plane of the equator.

For points in the Earth's Northern Hemisphere, latitudes are considered positive, or northern; for points in the Southern Hemisphere - negative, or southern.

Latitudes can range from -90° to +90° (or from 90° south latitude to 90° north latitude). The terms "longitude" and "latitude" have come down to us from ancient navigators who described the length and width of the Mediterranean Sea. The coordinate that corresponded to the measurements of the length of the Mediterranean Sea became longitude, and the one that corresponded to the width became the modern latitude.

Determination of latitude, like determination of the direction of the meridian, is closely related to the observation of stars. Astronomers of antiquity have already proved that the height of the celestial pole above the horizon is equal to the geographical latitude of the place.

A line on the surface of the Earth connecting points with the same latitude is called a parallel. The plane of any parallel is parallel to the plane of the earth's equator. Among the parallels, a special place is occupied by the tropics and the polar circles.

The sun makes a circuit of the celestial sphere during the year, moving along the ecliptic, inclined to the celestial equator (see Celestial Sphere) at an angle of 23.5 °. On the day of the vernal equinox, it is at the intersection of the ecliptic with the celestial equator and therefore at noon is observed at the zenith at the earth's equator.

Day by day, the Sun moves along the ecliptic to the northern hemisphere of the sky, its declination (see Celestial coordinates) increases, and in the following days at noon it passes overhead no longer at the Earth's equator, but at a latitude numerically equal to the Sun's declination. This continues until the summer solstice, when the declination of the Sun reaches its maximum value of +23.5°. On this day, the only time in the year it passes at noon through the zenith at the northern parallel + 23.5 °. This parallel is called the Northern Tropic, or the Tropic of Cancer (after the name of the zodiac constellation in which the point of the summer solstice was located in ancient times). On the day of the summer solstice, the zone of the polar day around the North Pole of the Earth extends to the parallel + 66.5 °, which is called the Arctic Circle (see Longitude of the day).

Six months later, on the day of the winter solstice, the Sun, whose declination takes on a value of -23.5 °, passes overhead only once a year at the latitude of the Southern Tropic, or Tropic of Capricorn, i.e., on a parallel with a latitude of -23.5 °. The southern parallel with a latitude of -66.5° is called the Antarctic Circle.

The astronomical determination of one of the geographic coordinates - latitude - is relatively simple. To do this, as mentioned above, it is sufficient to determine the height of the pole above the horizon. Astronomers of antiquity knew how to do this already in the III century. BC e. The measurement of longitude is associated with much greater difficulties. Only from some astronomical observations, without attracting additional information, longitude was not able to be determined either in antiquity or in the Middle Ages. This is connected, in particular, with the great delusion of Christopher Columbus, who, due to errors in determining longitude, having discovered the Bahamas, believed that he was sailing near the tip of Asia.

Geographic longitude is obtained as the difference between the local time (see Measuring time) of a given point and the local time of the initial meridian, taken as the prime meridian.

Previously, to determine longitude, observations were made of phenomena that occur almost simultaneously over vast areas of the earth's surface, for example, solar and lunar eclipses or eclipses of Jupiter's satellites.

It was done like this. Astronomers working on the zero meridian, using the results of many years of observations, predicted those moments at which the desired phenomenon occurs according to the local time of the zero meridian. These predictions were published in special tables. In the future, the astronomer-navigator or astronomer-traveler, from his measurements, established the moment of local time when the expected phenomenon occurred at the observation point. The result was compared with the table data. Since the phenomenon chosen for observation had to occur simultaneously for all parts of the Earth, the difference between the local time at the observation point and the local time indicated in the table for the zero meridian corresponded to the difference in longitude. A much more convenient way is "transportation of time". This method is as follows. The clock, set to the local time of the zero meridian, is transported to a given point on the Earth, and there their readings are compared with local time. But to apply the method of "transportation of time" in practice, you need a very reliable watch that can store the time of the zero meridian in a long journey. After all, a clock error of only 1 minute when determining longitude near the equator leads to an inaccuracy in determining the location on the Earth's surface by almost 30 km. Reliable mechanical clock-chronometers appeared only in the second half of the 18th century. in England.

With the invention of the telegraph, the time of the zero meridian began to be transmitted to observation points via electric wires. And then the telegraph was replaced by radio. The problem of determining geographic longitudes has ceased to exist in our time.

The geographic coordinates described above are called astronomical. Astronomical coordinates are inconvenient for building accurate topographic maps, since the plumb lines with which latitude measurements are associated change incorrectly when moving from one point on the earth's surface to another. The direction of plumb lines is greatly influenced by gravitational anomalies (see Gravimetry) associated with the features of the terrain and other causes.

Geodetic coordinates are more convenient for solving geodesy problems. In the geodetic coordinate system, the plumb line is the perpendicular to the earth's ellipsoid. Thus, the geodetic latitude is equal to the angle between the direction of the perpendicular to the earth's ellipsoid, drawn through a given point, and the plane of the ellipsoid's equator. It differs only slightly from the astronomical latitude.

Instead of a plumb line, you can use the radius vector of a given point on the Earth's surface, drawn from its center. A system of geographic coordinates obtained in this way is called geocentric.

The figure (p. 65) shows the section of the Earth along the meridian and the difference in geographical latitudes - astronomical, geodetic and geocentric.

By analogy with the system of geographic coordinates on Earth, similar systems are introduced on the surfaces of other planets and their satellites.

Two geographical coordinates - latitude and longitude - determine the position of a point on a regular geometric figure - a sphere or on an earth ellipsoid. For points of the real physical surface of the Earth, a third coordinate is introduced. The most commonly used for this purpose is the height above the geoid, the so-called height above sea level.

Measuring the height of points on the earth's surface above sea level is not an astronomical, but a geodetic task. The beginning of the calculation of heights is usually set by the results of long-term averaged observations of the water level in the seas with the help of special water meters - foot stocks. The height system on the territory of the USSR is based on the average water level of the Baltic Sea and originates from the zero of the Kronstadt footstock.

The earth has a spherical shape, more precisely, it is slightly flattened along the edges at the points that are its poles. But this is not particularly noticeable on the scale of the planet, because it is assumed that the Earth is a ball, and its surface is taken as spherical.

Marking the Earth with meridians and parallels made it possible to accurately determine the coordinates of any object that moves (airplane, thunderclouds), or that occupies a certain place on the planet (city, island). This gave quite a lot of advantages for 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 with the help of modern technologies, although if you suddenly find yourself on a desert island without the means so familiar to our lives - smartphones, tablets, laptops, respectively, without Internet access, without a navigator and other things, then it would not be superfluous to know those very "inconvenient" methods for calculating coordinates.

You can use a navigation system into which the desired coordinates will be entered, and the 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 coordinates have preoccupied the minds of people for a long time, even before our era. Hipparchus and Ptolemy were prominent scientists in the development of the coordinate system. These people lived in the second or first centuries BC, but, nevertheless, they could already determine with separation accuracy. These were the great people of their era, powerful geographers and astronomers. It was they who introduced the concept that we now call the coordinate system, and from their work it is already clear what it is. At that time, these people did not know that the Earth revolves around the Sun. Hipparchus suggested that the surface of our planet could be considered an ideal sphere, and using its example, he explained the various foundations regarding spherical geometry.

Globe - the most accurate model of the Earth

It is with the help of a globe that you can easily determine the coordinates of any country, island or other object. With its help, it is easiest to show what the meridians and parallels, geographic poles, other points and lines of the Earth are.

By the way, the first globe was created a long time ago, even before our era, and a certain Crates of Mallus made it in 150 BC, at the same time when Hipparchus and Ptolemy lived. Of course, a globe cannot show all the small details, but in general it allows you to perfectly describe the big picture of what our planet is, and perfectly demonstrates, for example, which points on the earth are called geographic poles,

On the globe, it is easy to see where any country, sea, ocean, location of the continents, or even their topography is located. It depends on what will be depicted by the creator of this or that globe. It can be purely political, only with the division of the continents into countries and with the indication of large objects such as oceans. Most likely it will be a small decorative globe. The training instances contain much more information about the geographic poles and geographic location of any part of the world.

In general, there are three parameters by which the Earth is characterized in geographic coordinate terms. Therefore, consider the main points, lines and planes on the surface of the Earth.

What is the Earth's axis

Is it possible to take the Earth for a ball, then it becomes clear that it has such a line, which also serves as a creative line in a stereometric figure. What exactly are we talking about? This is a line, which is a diameter, rotating around which, a semicircle creates a whole sphere. What diameter in comparison with the Earth is called the axis. This is an imaginary line that does not really exist, but there is a daily rotation around it, and it is commonly believed that it passes through the North and South Poles.

Poles of the planet Earth

What points on earth are called geographic poles? They are the well-known cold deserted north and south poles. In stereometry, what is called the "geographic pole" is the point at which the earth's axis of rotation (the diagonal of a spherical body) intersects the sphere. The last one in this case is

Through these two poles pass all the meridians, which will be discussed below.

What are parallels

Let's continue to consider the Earth as a sphere and define what the parallels are in this case. If we assume that the planet, like the ball, has a center, then the Earth's axis will pass through it and be divided into two equal parts, like a diameter into radii.

If we draw a certain plane that will pass perpendicular to the axis, then it will cross the sphere along a certain circle, that is, the Earth along a line called a parallel. The parallel, which has 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 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 geographic poles of the planet Earth, which are named depending on which part of the world they are in.

Meridian

If we draw a large plane through the axis itself and through the poles, we get the result of 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 shown on the map and on the globe, is a degree network.

It is two-dimensional, since it is given by only two coordinates - the parallel coordinate and the latitude coordinate. So what are geographic coordinates? These are two numbers, indicators of latitude and longitude. These numbers are in degrees and minutes.

At the beginning of the article, it was said that the Earth is not quite a sphere, that it is slightly flattened. What is it expressed in? The length of the equator is 40075.7 kilometers, when the length of the meridian is 40008.5 kilometers. The poles are a little closer to the equator, although this is not very noticeable on a planetary scale.

Planes of the earth's spheroid

It is those imaginary planes that run parallel or perpendicular to the earth's axis that 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 earth into the eastern and main plane, which passes through the equator and divides the earth into two parts - the northern and southern hemispheres.

Initial reference lines

All coordinates are calculated using conventional stereometry. Reference points are chosen, more precisely, reference meridian and reference parallel, from which the coordinates of any place on Earth are calculated. The zero meridian was chosen to be the one that passes through London, namely through the Greenwich Observatory. As a line, which is considered the origin of the 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 certain coordinates to a point, and it is called the World Geodetic System-84, or WGS-84 for short, (84 is the year the system was adopted), which is used by the whole world, and in which the zero meridian is the ERS Reference Meridian, passing near Greenwich, just 5.31 arc minutes to the east.

What lines of the earth give latitude and longitude

Children at school often confuse these concepts - meridians and parallels, which of them is the width and which is the longitude. So, the equator is the origin of the geographic latitude, when the Greenwich meridian is the starting line for calculating longitude.

Geographic latitude can have values ​​from 0 to 90 degrees. Depending on which side of the equator the point is located, it is assigned the value of northern latitude or southern latitude. So, let's say New York has a latitude of 40 degrees 43 minutes north, and Sydney has a latitude of 33 degrees 52 minutes south. It is written as follows: 40 about 43 ', 33 about 52 '.

Similarly with geographic longitude. It can also be calculated using degrees and minutes, but longitude has a range of values ​​from 0 to 180 degrees. It can be western if it goes west from the zero meridian, and eastern (similarly - east from the zero meridian).

As previously stated, the zero meridian passes through Greenwich and has a value of 0 degrees. And what points on the Earth are called the geographic poles of the planet and what are their coordinates? These are the points that have values ​​of ninety degrees in latitude and zero degrees in longitude.

Summing up

On the planet Earth, as well as on the sphere, there are basic points, lines and planes. What points on the earth are called geographical poles, we have already figured out. These are the points through which the diurnal axis passes. If the plane passes through this axis and crosses the geographic poles, then it forms the intersections of the Earth's sphere, which are called meridians.

There is a passing one in London, and several others that have a dimension of up to 180 degrees (there can be at least 180 of them). 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 with the greatest longitude is called the equator. It is he who is the initial for reading the latitude coordinates. 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 strokes are used to indicate seconds (such as for minutes).

The earth's axis crosses the surface of the planet at the points of the geographic poles.

Geographic poles

As you know, the Earth has two poles: North (located in the Arctic Ocean in the central part of the Arctic) and South (located on the Antarctic continent). These places do not belong to any state.

The South Pole is the southernmost point of the planet, and the North Pole, respectively, is the northernmost. A person standing exactly on the pole (for example, on the South) takes any step towards the north.

The areas surrounding the poles are the coldest on the planet and are called the Arctic. There are also two seasons of the year: polar night and polar day. This is due to the fact that the illumination here differs from the rest of the planet due to the deviation of the earth's axis from the plane of the orbit by about 20 °.

Conquest of the poles

The conquest of the poles was very slow and did not occur until the beginning of the twentieth century. People have been trying to conquer the North Pole since the seventeenth-eighteenth century, since all the continents around were inhabited for a long time and swimming in the southern parts of the Arctic Ocean took place over the centuries. However, during the short Arctic summer, it was not possible to sail there by sea, and icebreakers did not exist then.

In this regard, the North Pole was mastered only in 1909. The success of the expedition of the discoverer Robert Peary was guaranteed, in many respects, by the fact that the northern coast of Greenland, located closest to the pole, was chosen as the starting point. Other explorers tried to reach the Arctic from Europe, and they simply did not have enough supplies to complete the trip.

Other notable travelers who attempted to reach the North Pole included:

• F. Nansen.
• W. Parry.
• F. Cook.
• C. Hall.

Exploration of the Antarctic began much later, because. the continent itself was discovered only in the first half of the nineteenth century. It was reached by the Russian expedition of Bellingshausen. Only a few decades after that, people first set foot on the land of Antarctica. In 1911, several pioneers went to the pole at once, and in the end, the victory went to the Norwegian R. Amundsen.

One of the two points of intersection of the Earth's axis of rotation with the Earth's surface

The place on Earth with the longest nights

One of the two ends of a magnet

One of two opposite ends of an electrical circuit

One of the two points of intersection of the Earth's axis with the surface, as well as the area adjacent to this point

Singular point of an analytic function

Peren. pronounced opposites.

Positive or negative current source terminal

Polar Station, Amundsen-Scott, USA

Limit, border, extreme point of something

Central, main point, place

Meridian meeting point

One of the extreme points of the proposed axis of rotation of the Earth

Both North and South

Point with zero latitude and longitude

The place where bears rub their backs against the earth's axis

. "plus" or "minus" on the battery

magnet end

Geographical navel of the Earth

Top of the Earth

American polar station in Antarctica

Russian refrigerator brand

. "+" or "-" batteries

Magnetic south or north

. "minus" batteries

Center in the Arctic and Antarctica

A place with zero longitude and latitude

He was conquered by Sedov and Nansen

. "edge" of the earth

Intersection point of the Earth's axis of rotation with the surface

One of the two ends of a magnet

Positive or negative current source terminal

The end point of something

. "+" or "-" batteries

. "end" of the earth

. "minus" batteries

. battery positive or negative

M. Greek. awn, each of the end points of the axis on which the ball rotates. Earth's poles, north and south (ostia midnight and noon), points on the earth's surface through which the imaginary axis of the earth passes; heavenly ostia, corresponding to the earthly points of the meeting of the earth's axis with the (imaginary) heavenly firmament. The height of the pole, the earth's ostium above the ovid (horizon), is equal to the latitude of the place. The poles of any great circle of a ball, the meeting points of its axis with the surface of the ball. Poles or ostia of a magnet, a galvanic column or an electric bank, etc., two opposite points or planes that have an opposite effect; in a magnet, the north and south poles are distinguished, the ends with which a freely suspended magnet addresses these two cardinal points. The magnetic poles of the earth, the points near the awns, in which the greatest magnetic force is concentrated. The poles are also generally called the extreme points of forces opposite to each other (or mathematically, and - Pole or pole related to the pole. Polar, pole, core. Polar ice. Forces polar to each other, opposite. eye star, in the constellation Ursa Minor Polar circles, two imaginary circles separating the arctic belts around the poles, they are drawn by the end of the axis (ostium, pole) of the solar circle (ecliptic). Polarize light or a beam of light, change it by passing it through different media so that it reveals its duality.

The earth's axis crosses the surface of the planet at the points of the geographic poles.

Geographic poles

As you know, the Earth has two poles: North (located in the Arctic Ocean in the central part of the Arctic) and South (located on the Antarctic continent). These places do not belong to any state.

The South Pole is the southernmost point of the planet, and the North Pole, respectively, is the northernmost. A person standing exactly on the pole (for example, on the South) takes any step towards the north.

The areas surrounding the poles are the coldest on the planet and are called the Arctic. There are also two seasons of the year: polar night and polar day. This is due to the fact that the illumination here differs from the rest of the planet due to the deviation of the earth's axis from the plane of the orbit by about 20 °.

Conquest of the poles

The conquest of the poles was very slow and did not occur until the beginning of the twentieth century. People have been trying to conquer the North Pole since the seventeenth-eighteenth century, since all the continents around were inhabited for a long time and swimming in the southern parts of the Arctic Ocean took place over the centuries. However, during the short Arctic summer, it was not possible to sail there by sea, and icebreakers did not exist then.

In this regard, the North Pole was mastered only in 1909. The success of the expedition of the discoverer Robert Peary was guaranteed, in many respects, by the fact that the northern coast of Greenland, located closest to the pole, was chosen as the starting point. Other explorers tried to reach the Arctic from Europe, and they simply did not have enough supplies to complete the trip.

Other notable travelers who attempted to reach the North Pole included:

• F. Nansen.
• W. Parry.
• F. Cook.
• C. Hall.

Exploration of the Antarctic began much later, because. the continent itself was discovered only in the first half of the nineteenth century. It was reached by the Russian expedition of Bellingshausen. Only a few decades after that, people first set foot on the land of Antarctica. In 1911, several pioneers went to the pole at once, and in the end, the victory went to the Norwegian R. Amundsen.