What are geographic coordinates called? Latitude and longitude - what is it in geography

In Chapter 1, it was noted that the Earth has the shape of a spheroid, that is, an oblate ball. Since the earth's spheroid differs very little from a sphere, this spheroid is usually called the globe. The earth rotates around an imaginary axis. The points of intersection of the imaginary axis with the globe are called poles. North geographic pole (PN) is considered to be the one from which the Earth’s own rotation is seen counterclockwise. South geographic pole (PS) - the pole opposite to the north.
If you mentally cut the globe with a plane passing through the axis (parallel to the axis) of rotation of the Earth, we get an imaginary plane called meridian plane . The line of intersection of this plane with the earth's surface is called geographical (or true) meridian .
Plane perpendicular earth's axis and passing through the center globe, called plane of the equator , and the line of intersection of this plane with the earth’s surface is equator .
If you mentally cross the globe with planes parallel to the equator, then on the surface of the Earth you get circles called parallels .
The parallels and meridians marked on globes and maps are degree mesh (Fig. 3.1). The degree grid makes it possible to determine the position of any point on the earth's surface.
It is taken as the prime meridian when compiling topographic maps Greenwich astronomical meridian , passing through the former Greenwich Observatory (near London from 1675 - 1953). Currently, the buildings of the Greenwich Observatory house a museum of astronomical and navigational instruments. The modern prime meridian passes through Hurstmonceux Castle 102.5 meters (5.31 seconds) east of the Greenwich astronomical meridian. A modern prime meridian is used for satellite navigation.

Rice. 3.1. Degree grid of the earth's surface

Coordinates - angular or linear quantities that determine the position of a point on a plane, surface or in space. To determine coordinates on the earth's surface, a point is projected as a plumb line onto an ellipsoid. To determine the position of horizontal projections of a terrain point in topography, systems are used geographical , rectangular And polar coordinates .
Geographical coordinates determine the position of the point relative to the earth's equator and one of the meridians, taken as the initial one. Geographic coordinates can be obtained from astronomical observations or geodetic measurements. In the first case they are called astronomical , in the second - geodetic . In astronomical observations, the projection of points onto the surface is carried out by plumb lines, in geodetic measurements - by normals, therefore the values ​​of astronomical and geodetic geographical coordinates are somewhat different. To create small-scale geographic maps, the compression of the Earth is neglected, and the ellipsoid of revolution is taken as a sphere. In this case, the geographic coordinates will be spherical .
Latitude - an angular value that determines the position of a point on Earth in the direction from the equator (0º) to the North Pole (+90º) or the South Pole (-90º). Latitude is measured central angle in the plane of the meridian of a given point. On globes and maps, latitude is shown using parallels.

Rice. 3.2. Geographic latitude

Longitude - an angular value that determines the position of a point on Earth in the West-East direction from the Greenwich meridian. Longitudes are counted from 0 to 180°, to the east - with a plus sign, to the west - with a minus sign. On globes and maps, latitude is shown using meridians.

Rice. 3.3. Geographic longitude

3.1.1. Spherical coordinates

Spherical geographic coordinates are called angular values ​​(latitude and longitude) that determine the position of terrain points on the surface of the earth’s sphere relative to the plane of the equator and the prime meridian.

Spherical latitude (φ) called the angle between the radius vector (the line connecting the center of the sphere and a given point) and the equatorial plane.

Spherical longitude (λ) - this is the angle between the plane of the prime meridian and the meridian plane of a given point (the plane passes through the given point and the axis of rotation).

Rice. 3.4. Geographic spherical coordinate system

In topography practice, a sphere with radius R = 6371 is used km, the surface of which is equal to the surface of the ellipsoid. On such a sphere, the arc length of the great circle is 1 minute (1852 m) called nautical mile.

3.1.2. Astronomical coordinates

Astronomical geographic coordinates are latitude and longitude that determine the position of points on geoid surface relative to the plane of the equator and the plane of one of the meridians, taken as the initial one (Fig. 3.5).

Astronomical latitude (φ) is the angle formed by a plumb line passing through a given point and a plane perpendicular to the axis of rotation of the Earth.

Plane of the astronomical meridian - a plane passing through a plumb line at a given point and parallel to the Earth’s axis of rotation.
Astronomical meridian - line of intersection of the geoid surface with the plane of the astronomical meridian.

Astronomical longitude (λ) is the dihedral angle between the plane of the astronomical meridian passing through a given point and the plane of the Greenwich meridian, taken as the initial one.

Rice. 3.5. Astronomical latitude (φ) and astronomical longitude (λ)

3.1.3. Geodetic coordinate system

IN geodetic geographic coordinate system the surface on which the positions of points are found is taken to be the surface reference -ellipsoid . The position of a point on the surface of the reference ellipsoid is determined by two angular quantities - geodetic latitude (IN) and geodetic longitude (L).
Geodesic meridian plane - a plane passing through the normal to the surface of the earth's ellipsoid at a given point and parallel to its minor axis.
Geodetic meridian - the line along which the plane of the geodesic meridian intersects the surface of the ellipsoid.
Geodetic parallel - the line of intersection of the surface of the ellipsoid with a plane passing through a given point and perpendicular to the minor axis.

Geodetic latitude (IN)- the angle formed by the normal to the surface of the earth's ellipsoid at a given point and the plane of the equator.

Geodetic longitude (L)- dihedral angle between the plane of the geodesic meridian of a given point and the plane of the initial geodesic meridian.

Rice. 3.6. Geodetic latitude (B) and geodetic longitude (L)

3.2. DETERMINING GEOGRAPHICAL COORDINATES OF POINTS ON THE MAP

Topographic maps are printed in separate sheets, the sizes of which are set for each scale. The side frames of the sheets are meridians, and the top and bottom frames are parallels. . (Fig. 3.7). Hence, geographic coordinates can be determined by the side frames of a topographic map . On all maps, the top frame always faces north.
Geographic latitude and longitude are written in the corners of each sheet of the map. On maps of the Western Hemisphere in the northwest corner of the frame of each sheet to the right of the value meridian longitude the inscription is placed: “West of Greenwich.”
On maps of scales 1: 25,000 - 1: 200,000, the sides of the frames are divided into segments equal to 1′ (one minute, Fig. 3.7). These segments are shaded every other and separated by dots (except for a map of scale 1: 200,000) into parts of 10" (ten seconds). On each sheet, maps of scales 1: 50,000 and 1: 100,000 show, in addition, the intersection of the middle meridian and the middle parallel with digitization in degrees and minutes, and along the inner frame - outputs of minute divisions with strokes 2 - 3 mm long. This allows, if necessary, to draw parallels and meridians on a map glued from several sheets.

Rice. 3.7. Side map frames

When drawing up maps of scales 1: 500,000 and 1: 1,000,000, a cartographic grid of parallels and meridians is applied to them. Parallels are drawn at 20′ and 40″ (minutes), respectively, and meridians at 30′ and 1°.
The geographic coordinates of a point are determined from the nearest southern parallel and from the nearest western meridian, the latitude and longitude of which are known. For example, for a map of scale 1: 50,000 “ZAGORYANI”, the nearest parallel located to the south of a given point will be the parallel of 54º40′ N, and the nearest meridian located to the west of the point will be the meridian 18º00′ E. (Fig. 3.7).

Rice. 3.8. Determination of geographical coordinates

To determine the latitude of a given point you need to:

• set one leg of the measuring compass to a given point, set the other leg at the shortest distance to the nearest parallel (for our map 54º40′);
• Without changing the angle of the measuring compass, install it on the side frame with minute and second divisions, one leg should be at the southern parallel (for our map 54º40′), and the other between the 10-second points on the frame;
• count the number of minutes and seconds from the southern parallel to the second leg of the measuring compass;
• add the result to the southern latitude (for our map 54º40′).

To determine the longitude of a given point you need to:

• set one leg of the measuring compass to a given point, set the other leg at the shortest distance to the nearest meridian (for our map 18º00′);
• without changing the angle of the measuring compass, install it on the nearest horizontal frame with minute and second divisions (for our map, the lower frame), one leg should be on the nearest meridian (for our map 18º00′), and the other - between the 10-second points on horizontal frame;
• count the number of minutes and seconds from the western (left) meridian to the second leg of the measuring compass;
• add the result to the longitude of the western meridian (for our map 18º00′).

note that this method of determining the longitude of a given point for maps of scale 1:50,000 and smaller has an error due to the convergence of the meridians that limit the topographic map from the east and west. The north side of the frame will be shorter than the south. Consequently, discrepancies between longitude measurements on the north and south frames may differ by several seconds. To achieve high accuracy in the measurement results, it is necessary to determine the longitude on both the southern and northern sides of the frame, and then interpolate.
To increase the accuracy of determining geographic coordinates, you can use graphic method. To do this, it is necessary to connect the ten-second divisions of the same name closest to the point with straight lines in latitude to the south of the point and in longitude to the west of it. Then determine the sizes of the segments in latitude and longitude from the drawn lines to the position of the point and sum them accordingly with the latitude and longitude of the drawn lines.
The accuracy of determining geographic coordinates using maps of scales 1: 25,000 - 1: 200,000 is 2" and 10" respectively.

3.3. POLAR COORDINATE SYSTEM

Polar coordinates are called angular and linear quantities that determine the position of a point on the plane relative to the origin of coordinates, taken as the pole ( ABOUT), and polar axis ( OS) (Fig. 3.1).

Location of any point ( M) is determined by the position angle ( α ), measured from the polar axis to the direction to the determined point, and the distance (horizontal distance - projection of the terrain line onto the horizontal plane) from the pole to this point ( D). Polar angles are usually measured from the polar axis in a clockwise direction.

Rice. 3.9. Polar coordinate system

The following can be taken as the polar axis: the true meridian, the magnetic meridian, the vertical grid line, the direction to any landmark.

3.2. BIPOLAR COORDINATE SYSTEMS

Bipolar coordinates are called two angular or two linear quantities that determine the location of a point on a plane relative to two initial points (poles ABOUT 1 And ABOUT 2 rice. 3.10).

The position of any point is determined by two coordinates. These coordinates can be either two position angles ( α 1 And α 2 rice. 3.10), or two distances from the poles to the determined point ( D 1 And D 2 rice. 3.11).

Rice. 3.11. Determining the location of a point by two distances

In a bipolar coordinate system, the position of the poles is known, i.e. the distance between them is known.

3.3. POINT HEIGHT

Were previously reviewed plan coordinate systems , defining the position of any point on the surface of the earth's ellipsoid, or reference ellipsoid , or on a plane. However, these plan coordinate systems do not allow one to obtain an unambiguous position of a point on the physical surface of the Earth. Geographic coordinates relate the position of a point to the surface of the reference ellipsoid, polar and bipolar coordinates relate the position of a point to a plane. And all these definitions do not in any way relate to the physical surface of the Earth, which for a geographer is more interesting than the reference ellipsoid.
Thus, plan coordinate systems do not make it possible to unambiguously determine the position of a given point. It is necessary to somehow define your position, at least with the words “above” and “below”. Just regarding what? For getting complete information about the position of a point on the physical surface of the Earth, the third coordinate is used - height . Therefore, there is a need to consider the third coordinate system - height system .

The distance along a plumb line from a level surface to a point on the physical surface of the Earth is called height.

There are heights absolute , if they are counted from the level surface of the Earth, and relative (conditional ), if they are counted from an arbitrary level surface. Usually, the starting point for absolute heights is taken to be the ocean level or open sea in a calm state. In Russia and Ukraine, the starting point for absolute altitude is taken to be zero of the Kronstadt footstock.

Footstock- a rail with divisions, fixed vertically on the shore so that it is possible to determine from it the position of the water surface in a calm state.
Kronstadt footstock- a line on a copper plate (board) mounted in the granite abutment of the Blue Bridge of the Obvodny Canal in Kronstadt.
The first footpole was installed during the reign of Peter 1, and from 1703 regular observations of the level began Baltic Sea. Soon the footstock was destroyed, and only from 1825 (and to the present) regular observations were resumed. In 1840, hydrographer M.F. Reinecke calculated the average height of the Baltic Sea level and recorded it on the granite abutment of the bridge in the form of a deep horizontal line. Since 1872, this line has been taken as the zero mark when calculating the heights of all points on the territory Russian state. The Kronstadt footing rod was modified several times, but the position of its main mark was kept the same during design changes, i.e. defined in 1840
After the breakup Soviet Union Ukrainian surveyors did not invent their own national height system, and currently in Ukraine it is still used Baltic height system.

It should be noted that in every necessary case, measurements are not taken directly from the level of the Baltic Sea. There are special points on the ground, the heights of which were previously determined in the Baltic height system. These points are called benchmarks .
Absolute altitudes H can be positive (for points above the Baltic Sea level), and negative (for points below the Baltic Sea level).
The difference in absolute heights of two points is called relative height or exceeding (h):
h =H A−H IN .
The excess of one point over another can also be positive or negative. If the absolute height of a point A greater than the absolute height of the point IN, i.e. is above the point IN, then the point is exceeded A above the point IN will be positive, and vice versa, exceeding the point IN above the point A- negative.

Example. Absolute heights of points A And IN: N A = +124,78 m; N IN = +87,45 m. Find mutual excesses of points A And IN.

Solution. Exceeding point A above the point IN
h A(B) = +124,78 - (+87,45) = +37,33 m.
Exceeding point IN above the point A
h B(A) = +87,45 - (+124,78) = -37,33 m.

Example. Absolute point height A equal to N A = +124,78 m. Exceeding point WITH above the point A equals h C(A) = -165,06 m. Find the absolute height of a point WITH.

Solution. Absolute point height WITH equal to
N WITH = N A + h C(A) = +124,78 + (-165,06) = - 40,28 m.

The numerical value of the height is called the point elevation (absolute or conditional).
For example, N A = 528.752 m - absolute point elevation A; N" IN = 28.752 m - reference point elevation IN .

Rice. 3.12. Heights of points on the earth's surface

To move from conditional heights to absolute ones and vice versa, you need to know the distance from the main level surface to the conditional one.

Video
Meridians, parallels, latitudes and longitudes
Determining the position of points on the earth's surface

Questions and tasks for self-control

1. Expand the concepts: pole, equatorial plane, equator, meridian plane, meridian, parallel, degree grid, coordinates.
2. Relative to what planes on the globe (ellipsoid of revolution) are geographic coordinates determined?
3. What is the difference between astronomical geographic coordinates and geodetic ones?
4. Using a drawing, explain the concepts of “spherical latitude” and “spherical longitude”.
5. On what surface is the position of points in the astronomical coordinate system determined?
6. Using a drawing, explain the concepts of “astronomical latitude” and “astronomical longitude”.
7. On what surface are the positions of points determined in a geodetic coordinate system?
8. Using a drawing, explain the concepts of “geodetic latitude” and “geodetic longitude”.
9. Why is it necessary to connect the ten-second divisions of the same name closest to the point with straight lines to increase the accuracy of determining longitude?
10. How can you calculate the latitude of a point by determining the number of minutes and seconds from the northern frame of a topographic map?
11. What coordinates are called polar?
12. What purpose does the polar axis serve in a polar coordinate system?
13. What coordinates are called bipolar?
14. What is the essence of the direct geodetic problem?

We suggest using a similar service from Google - + location interesting places in the world on the Google Maps diagram

Calculation of the distance between two points by coordinates:

Online calculator - calculating the distance between two cities, points. Their exact location in the world can be found at the link above

Countries in alphabetical order:

Determining latitude and longitude on a map?

On the page you can quickly determine coordinates on the map - find out the latitude and longitude of the city. Online search for streets and houses by address, using GPS, to determine coordinates on a Yandex map, how to find a location - described in more detail below.

Determining the geographical coordinates of any city in the world (find out latitude and longitude) by online map from the Yandex service is actually a very simple process. You have two convenient options, let’s take a closer look at each of them.

Fill out the form: Rostov-on-Don Pushkinskaya 10 (with the help and if you have the house number, the search will be more accurate). In the upper right corner there is a form for determining coordinates, which contains 3 precise parameters - the coordinates of the mark, the center of the map and the zoom scale.

After activating the “Find” search, each field will contain the necessary data - longitude and latitude. Look at the “Center of the map” field.

Second option: In this case it’s even simpler. Interactive world map with coordinates contains a marker. By default, it is located in the center of Moscow. You need to drag the label and place it on the desired city, for example, determine the coordinates on. The latitude and longitude will automatically match the search object. Look at the “Mark Coordinates” field.

When searching the desired city or countries, use the navigation and zoom tools. By zooming in and out +/-, and also moving the interactive map itself, it is easy to find any country or search for a region on the world map. This way you can find the geographic center of Ukraine or Russia. In the country of Ukraine, this is the village of Dobrovelichkovka, which is located on the Dobraya River, Kirovograd region.

Copy the geographic coordinates of the center of Ukraine urban settlement. Dobrovelychkovka — Ctrl+C

48.3848,31.1769 48.3848 north latitude and 31.1769 east longitude

Longitude +37° 17′ 6.97″ E (37.1769)

Latitude +48° 38′ 4.89″ N (48.3848)

At the entrance to the urban settlement there is a sign notifying about this interesting fact. It will most likely be uninteresting to examine its territory. There are much more interesting places in the world.

How to find a place on the map using coordinates?

Let's consider the reverse process, for example. Why do you need to determine latitude and longitude on a map? Let's say you need to determine by GPS coordinates navigator shows the exact location of the car on the diagram. Or close friend will call on a day off and tell you the coordinates of his location, inviting you to join a hunt or fishing.

Knowing the exact geographic coordinates, you will need a map with latitude and longitude. It is enough to enter your data into the search form from the Yandex service to determine the location by coordinates successfully. Example, enter the latitude and longitude of Moskovskaya street 66 in the city of Saratov - 51.5339,46.0368. The service will quickly determine and display the location of a given house in the city as a mark.

In addition to the above, you can easily determine the coordinates on the map of any metro station in the city. After the name of the city we write the name of the station. And we observe where the mark is located and its coordinates with latitude and longitude. To determine the length of the route, you need to use the “Ruler” tool (measuring distances on the map). We put a mark at the beginning of the route and then at end point. The service will automatically determine the distance in meters and show the track itself on the map.

It is possible to more accurately examine a place on the map thanks to the “Satellite” diagram (upper corner on the right). Look what it looks like. You can do all of the above operations with it.

World map with longitude and latitude

Imagine you are in an unfamiliar area, and there are no objects or landmarks nearby. And there is no one to ask! How could you explain your exact location so that you can be found quickly?

Thanks to concepts such as latitude and longitude, you can be detected and found. Latitude shows the location of an object in relation to the South and North Poles. The equator is considered to be zero latitude. The South Pole is located at 90 degrees. south latitude, and North at 90 degrees north latitude.

This data turns out to be insufficient. It is also necessary to know the situation in relation to the East and West. This is where the longitude coordinate comes in handy.

Cartographic data of cities in Russia, Ukraine and the world

Globes and geographic maps have a coordinate system. With its help, you can plot any object on a globe or map, as well as find it on the earth's surface. What is this system, and how to determine the coordinates of any object on the surface of the Earth with its participation? We will try to talk about this in this article.

Geographic latitude and longitude

Longitude and latitude are geographical concepts that are measured in angular units (degrees). They serve to indicate the position of any point (object) on the earth's surface.

Geographic latitude is the angle between a plumb line at a particular point and the plane of the equator (zero parallel). Latitude in Southern Hemisphere called southern, and in the Northern Hemisphere – northern. Can vary from 0∗ to 90∗.

Geographic longitude is the angle made by the meridian plane at a certain point to the plane of the prime meridian. If the longitude is counted east from the prime Greenwich meridian, then it will be east longitude, and if it is to the west, then it will be west longitude. Longitude values ​​can range from 0∗ to 180∗. Most often, on globes and maps, meridians (longitude) are indicated when they intersect with the equator.

How to determine your coordinates

If a person gets into emergency he must, first of all, be well versed in the terrain. In some cases, it is necessary to have certain skills in determining the geographic coordinates of your location, for example, in order to convey them to rescuers. There are several ways to do this using improvised methods. We present the simplest of them.

Determining longitude by gnomon

If you go traveling, it is best to set your watch to Greenwich time:

• It is necessary to determine when it will be noon GMT in a given area.
• Stick a stick (gnomon) to determine the shortest solar shadow at noon.
• Find the minimum shadow cast by the gnomon. This time will be local noon. In addition, this shadow will point strictly north at this time.
• Using this time, calculate the longitude of the place where you are.

Calculations are made based on the following:

• since the Earth makes a complete revolution in 24 hours, therefore, it will travel 15 ∗ (degrees) in 1 hour;
• 4 minutes of time will be equal to 1 geographical degree;
• 1 second of longitude will be equal to 4 seconds of time;
• if noon occurs before 12 o'clock GMT, this means that you are in the Eastern Hemisphere;
• If you spot the shortest shadow after 12 o'clock GMT, then you are in the Western Hemisphere.

An example of the simplest calculation of longitude: the shortest shadow was cast by the gnomon at 11 hours 36 minutes, that is, noon came 24 minutes earlier than at Greenwich. Based on the fact that 4 minutes of time are equal to 1 ∗ longitude, we calculate - 24 minutes / 4 minutes = 6 ∗. This means that you are in the Eastern Hemisphere at 6 ∗ longitude.

How to determine geographic latitude

The determination is made using a protractor and a plumb line. To do this, a protractor is made from 2 rectangular strips and fastened in the form of a compass so that the angle between them can be changed.

• A thread with a load is fixed in the central part of the protractor and plays the role of a plumb line.
• With its base, the protractor is aimed at the North Star.
• 90 ∗ is subtracted from the angle between the plumb line of the protractor and its base. The result is the angle between the horizon and North Star. Since this star is only 1 ∗ deviated from the axis of the world pole, the resulting angle will be equal to the latitude of the place where you are given time you are.

How to determine geographic coordinates

The simplest way to determine geographic coordinates, which does not require any calculations, is this:

• Google maps opens.
• Find the exact place there;
  • the map is moved with the mouse, moved away and zoomed in using its wheel
  • find locality by name using search.
• Right-click on the desired location. Select the required item from the menu that opens. IN in this case“What is here?” Geographic coordinates will appear in the search line at the top of the window. For example: Sochi - 43.596306, 39.7229. They mean geographic latitude and the longitude of the center of this city. This way you can determine the coordinates of your street or house.

Using the same coordinates you can see the place on the map. You just can’t swap these numbers. If you put longitude first and latitude second, you risk ending up in a different place. For example, instead of Moscow you will end up in Turkmenistan.

How to determine coordinates on a map

To determine the geographic latitude of an object, you need to find the closest parallel to it from the equator. For example, Moscow is located between the 50th and 60th parallels. The closest parallel from the equator is the 50th. To this figure is added the number of degrees of the meridian arc, which is calculated from the 50th parallel to the desired object. This number is 6. Therefore, 50 + 6 = 56. Moscow lies on the 56th parallel.

For determining geographic longitude the object is found on the meridian where it is located. For example, St. Petersburg lies east of Greenwich. Meridian, this one is 30 ∗ away from the prime meridian. This means that the city of St. Petersburg is located in the Eastern Hemisphere at a longitude of 30 ∗.

How to determine the coordinates of the geographic longitude of the desired object if it is located between two meridians? At the very beginning, the longitude of the meridian that is located closer to Greenwich is determined. Then to given value it is necessary to add the number of degrees that is on the parallel arc the distance between the object and the meridian closest to Greenwich.

Example, Moscow is located east of the 30 ∗ meridian. Between it and Moscow the arc of parallel is 8 ∗. This means that Moscow has an eastern longitude and it is equal to 38 ∗ (E).

How to determine your coordinates on topographic maps? Geodetic and astronomical coordinates of the same objects differ on average by 70 m. Parallels and meridians on topographic maps are the inner frames of the sheets. Their latitude and longitude are written in the corner of each sheet. Western Hemisphere map sheets are marked "West of Greenwich" in the northwest corner of the frame. Maps of the Eastern Hemisphere will accordingly be marked “East of Greenwich.”

Geographic longitude and latitude are used to accurately determine the physical location of any object on the globe. The most in a simple way Finding geographic coordinates is using a geographic map. This method requires some theoretical knowledge to implement it. How to determine longitude and latitude is described in the article.

Geographical coordinates

Coordinates in geography are a system in which each point on the surface of our planet is assigned a set of numbers and symbols that allows the precise location of that point to be determined. Geographic coordinates are expressed in three numbers - latitude, longitude and altitude above sea level. The first two coordinates, that is, latitude and longitude, are most often used in various geographical problems. The origin of the report in the geographic coordinate system is at the center of the Earth. To represent latitude and longitude, spherical coordinates are used, which are expressed in degrees.

Before considering the question of how to determine longitude and latitude by geography, you should understand these concepts in more detail.

The concept of latitude

The latitude of a specific point on the Earth's surface is understood as the angle between the equatorial plane and the line connecting this point with the center of the Earth. Through all points of the same latitude, you can draw a plane that will be parallel to the plane of the equator.

The equatorial plane is the zero parallel, that is, its latitude is 0°, and it divides the entire globe into the southern and northern hemispheres. Accordingly, the north pole lies at the parallel of 90° north latitude, and the south pole lies at the parallel of 90° south latitude. The distance that corresponds to 1° when moving along a particular parallel depends on what kind of parallel it is. As latitude increases, moving north or south, this distance decreases. Therefore, is 0°. Knowing that the circumference of the Earth at the latitude of the equator has a length of 40075.017 km, we obtain the length of 1° along this parallel equal to 111.319 km.

Latitude shows how far north or south a given point on the Earth's surface lies from the equator.

The concept of longitude

The longitude of a specific point on the Earth's surface is understood as the angle between the plane passing through this point and the Earth's axis of rotation, and the plane of the prime meridian. According to the settlement agreement, the zero meridian is the one that passes through the Royal Observatory at Greenwich, located in the southeast of England. The Greenwich meridian divides the globe into eastern and

Thus, each line of longitude passes through the north and south pole. The lengths of all meridians are equal and amount to 40007.161 km. If we compare this figure with the length of the zero parallel, we can say that the geometric shape of planet Earth is a ball flattened at the poles.

Longitude shows how far west or east of the prime (Greenwich) meridian a specific point on Earth lies. If latitude has a maximum value of 90° (the latitude of the poles), then the maximum value of longitude is 180° west or east of the prime meridian. The 180° meridian is known as the International Date Line.

One might wonder interesting question, the longitude of which points cannot be determined. Based on the definition of a meridian, we find that all 360 meridians pass through two points on the surface of our planet; these points are the south and north poles.

Geographical degree

From the above figures it is clear that 1° on the Earth’s surface corresponds to a distance of more than 100 km, either along a parallel or along a meridian. For more accurate coordinates of an object, the degree is divided into tenths and hundredths, for example, they say 35.79 north latitude. This type of information is provided by satellite navigation systems such as GPS.

Ordinary geographic and topographic maps Fractions of a degree are expressed as minutes and seconds. Thus, each degree is divided into 60 minutes (denoted by 60"), and each minute is divided into 60 seconds (denoted by 60"). An analogy can be drawn here with the idea of ​​measuring time.

Getting to know the geographic map

To understand how to determine geographic latitude and longitude on a map, you must first become familiar with it. In particular, you need to understand how longitude and latitude coordinates are represented on it. Firstly, the top part of the map shows the northern hemisphere, the bottom part shows the southern hemisphere. The numbers on the left and right sides of the map indicate latitude, and the numbers on the top and bottom of the map indicate longitude coordinates.

Before determining the latitude and longitude coordinates, you need to remember that they are presented on the map in degrees, minutes and seconds. This system of units should not be confused with decimal degrees. For example, 15" = 0.25°, 30" = 0.5°, 45"" = 0.75".

Using a geographic map to determine longitude and latitude

We will explain in detail how to determine longitude and latitude by geography using a map. To do this, you first need to purchase a standard geographical map. This map can be a map of a small area, a region, a country, a continent, or the entire world. To understand which card you are dealing with, you should read its name. At the bottom, under the name, the limits of latitude and longitude that are presented on the map can be given.

After this, you need to select a certain point on the map, some object that needs to be marked in some way, for example, with a pencil. How to determine the longitude of an object located at a selected point, and how to determine its latitude? The first step is to find the vertical and horizontal lines that lie closest to the selected point. These lines are latitude and longitude, the numerical values ​​of which can be seen at the edges of the map. Let's assume that the selected point lies between 10° and 11° north latitude and 67° and 68° west longitude.

Thus, we know how to determine the geographic latitude and longitude of the object selected on the map with the accuracy that the map provides. In this case, the accuracy is 0.5°, both in latitude and longitude.

Determining the exact value of geographic coordinates

How to determine the longitude and latitude of a point more accurately than 0.5°? First you need to find out what scale the map you are working with is on. Typically, a scale bar is indicated in one of the corners of the map, showing the correspondence of distances on the map to distances in geographic coordinates and in kilometers on the ground.

After you have found a scale ruler, you need to take a simple ruler with millimeter divisions and measure the distance on the scale ruler. Let, in the example under consideration, 50 mm correspond to 1° latitude and 40 mm correspond to 1° longitude.

Now we position the ruler so that it is parallel to the lines of longitude drawn on the map, and measure the distance from the point in question to one of the nearest parallels, for example, the distance to the 11° parallel is 35 mm. We make a simple proportion and find that this distance corresponds to 0.3° from the 10° parallel. Thus, the latitude of the point in question is +10.3° (the plus sign means north latitude).

Similar steps should be done for longitude. To do this, place the ruler parallel to the lines of latitude and measure the distance to the nearest meridian from the selected point on the map, let’s say this distance is 10 mm to the meridian 67° west longitude. According to the rules of proportion, we find that the longitude of the object in question is -67.25° (the minus sign means western longitude).

Converting the received degrees into minutes and seconds

As stated above, 1° = 60" = 3600". Using this information and the rule of proportion, we find that 10.3° corresponds to 10°18"0". For the longitude value we get: 67.25° = 67°15"0". In this case, the proportion was used for conversion once for longitude and latitude. However, in the general case, when after using the proportion once fractional values ​​of minutes are obtained, it should be use the proportion a second time to get the value of incremental seconds. Note that the accuracy of determining coordinates up to 1" corresponds to an accuracy on the surface of the globe equal to 30 meters.

Recording received coordinates

After the question of how to determine the longitude of an object and its latitude has been answered, and the coordinates of the selected point have been determined, they should be written down correctly. The standard form of notation is to indicate longitude after latitude. Both values ​​must be specified with as many decimal places as possible, since this determines the accuracy of the object's location.

Defined coordinates can be represented in two different formats:

1. Using only the degree icon, for example +10.3°, -67.25°.
2. Using minutes and seconds, for example 10°18"0""N, 67°15"0""W.

It should be noted that in the case of representing geographic coordinates only using degrees, the words “north (south) latitude” and “east (west) longitude” are replaced by the corresponding plus or minus sign.

For determining latitude It is necessary, using a triangle, to lower the perpendicular from point A to the degree frame onto the line of latitude and read the corresponding degrees, minutes, seconds on the right or left along the latitude scale. φА= φ0+ Δφ

φА=54 0 36 / 00 // +0 0 01 / 40 //= 54 0 37 / 40 //

For determining longitude you need to use a triangle to lower a perpendicular from point A to the degree frame of the line of longitude and read the corresponding degrees, minutes, seconds from above or below.

Determining the rectangular coordinates of a point on the map

The rectangular coordinates of the point (X, Y) on the map are determined in the square of the kilometer grid as follows:

1. Using a triangle, perpendiculars are lowered from point A to the kilometer grid line X and Y and the values ​​are taken XA=X0+Δ X; UA=U0+Δ U

For example, the coordinates of point A are: XA = 6065 km + 0.55 km = 6065.55 km;

UA = 4311 km + 0.535 km = 4311.535 km. (the coordinate is reduced);

Point A is located in the 4th zone, as indicated by the first digit of the coordinate at given.

9. Measuring the lengths of lines, directional angles and azimuths on the map, determining the angle of inclination of the line specified on the map.

Measuring lengths

To determine on a map the distance between terrain points (objects, objects), using a numerical scale, you need to measure on the map the distance between these points in centimeters and multiply the resulting number by the scale value.

A small distance is easier to determine using a linear scale. To do this, it is enough to apply a measuring compass, the opening of which is equal to the distance between given points on the map, to a linear scale and take a reading in meters or kilometers.

To measure curves, the “step” of the measuring compass is set so that it corresponds to an integer number of kilometers, and an integer number of “steps” is plotted on the segment measured on the map. The distance that does not fit into the whole number of “steps” of the measuring compass is determined using a linear scale and added to the resulting number of kilometers.

Measuring directional angles and azimuths on a map

.

We connect points 1 and 2. We measure the angle. The measurement is carried out using a protractor, it is located parallel to the median, then the angle of inclination is reported clockwise.

Determining the angle of inclination of a line specified on the map.

The determination follows exactly the same principle as finding the directional angle.

10. Direct and inverse geodetic problem on a plane. When performing computational processing of measurements taken on the ground, as well as when designing engineering structures and making calculations to transfer projects into reality, the need arises to solve direct and inverse geodetic problems. Direct geodetic problem . By known coordinates X 1 and at 1 point 1, directional angle 1-2 and distance d 1-2 to point 2 you need to calculate its coordinates X 2 ,at 2 .

The coordinates of point 2 are calculated using the formulas (Fig. 3.5): (3.4) where X,atcoordinate increments equal to

(3.5)

Inverse geodetic problem . By known coordinates X 1 ,at 1 points 1 and X 2 ,at 2 points 2 need to calculate the distance between them d 1-2 and directional angle 1-2. From formulas (3.5) and Fig. 3.5 it is clear that. (3.6) To determine the directional angle 1-2, we use the arctangent function. At the same time, we take into account that computer programs and microcalculators give the main value of the arctangent= , lying in the range90+90, while the desired directional anglecan have any value in the range 0360.

The formula for transition from kdepends on the coordinate quarter in which the given direction is located or, in other words, on the signs of the differences y=y 2 y 1 and  x=X 2 X 1 (see table 3.1 and figure 3.6). Table 3.1

Rice. 3.6. Directional angles and main arctangent values ​​in the I, II, III and IV quarters

The distance between points is calculated using the formula

(3.6) or in another way - according to the formulas (3.7)

In particular, electronic tacheometers are equipped with programs for solving direct and inverse geodetic problems, which makes it possible to directly determine the coordinates of observed points during field measurements and calculate angles and distances for alignment work.