Determination of coordinates on the map. Geographic coordinates and their definition on the map

Video lesson “Geographical latitude and geographical longitude. Geographical coordinates will help you get an idea of ​​the geographic latitude and geographic longitude. The teacher will tell you how to correctly determine the geographical coordinates.

Geographic latitude- the length of the arc in degrees from the equator to the given point.

To determine the latitude of an object, you need to find the parallel on which this object is located.

For example, the latitude of Moscow is 55 degrees and 45 minutes north latitude, it is written as follows: Moscow 55 ° 45 "N; New York latitude - 40 ° 43" N; Sydney - 33°52"S

Geographic longitude is determined by meridians. Longitude can be western (from 0 meridian west to 180 meridian) and eastern (from 0 meridian east to 180 meridian). Longitudes are measured in degrees and minutes. Geographic longitude can have values ​​from 0 to 180 degrees.

Geographic longitude- length of the arc of the equator in degrees from the initial meridian (0 degrees) to the meridian of the given point.

The prime meridian is the Greenwich meridian (0 degrees).

Rice. 2. Definition of longitudes ()

To determine longitude, you need to find the meridian on which the given object is located.

For example, the longitude of Moscow is 37 degrees and 37 minutes of east longitude, it is written as follows: 37 ° 37 "E; the longitude of Mexico City is 99 ° 08" W.

Rice. 3. Geographic latitude and geographic longitude

To accurately determine the location of an object on the surface of the Earth, you need to know its geographic latitude and geographic longitude.

Geographical coordinates- quantities that determine the position of a point on the earth's surface using latitudes and longitudes.

For example, Moscow has the following geographic coordinates: 55°45" N and 37°37" E. The city of Beijing has the following coordinates: 39°56′ N 116°24′ E The latitude value is written first.

Sometimes you need to find an object by already given coordinates, for this you must first assume in which hemispheres this object is located.

Homework

Paragraphs 12, 13.

1. What is geographic latitude and longitude?

Bibliography

Main

1. Initial course of geography: Proc. for 6 cells. general education institutions / T.P. Gerasimova, N.P. Neklyukov. - 10th ed., stereotype. - M.: Bustard, 2010. - 176 p.

2. Geography. Grade 6: atlas. - 3rd ed., stereotype. - M.: Bustard, DIK, 2011. - 32 p.

3. Geography. Grade 6: atlas. - 4th ed., stereotype. - M.: Bustard, DIK, 2013. - 32 p.

4. Geography. 6 cells: cont. cards. - M.: DIK, Bustard, 2012. - 16 p.

Encyclopedias, dictionaries, reference books and statistical collections

1. Geography. Modern illustrated encyclopedia / A.P. Gorkin. - M.: Rosmen-Press, 2006. - 624 p.

Literature for preparing for the GIA and the Unified State Examination

1. Geography: an initial course. Tests. Proc. allowance for students 6 cells. - M.: Humanit. ed. center VLADOS, 2011. - 144 p.

2. Tests. Geography. Grades 6-10: Teaching aid / A.A. Letyagin. - M .: LLC "Agency" KRPA "Olimp": "Astrel", "AST", 2001. - 284 p.

Materials on the Internet

1. Federal Institute of Pedagogical Measurements ().

2. Russian Geographical Society ().

Instruction

See how the position of the mainland relates to other continents, the equator, the north and south poles, in which hemisphere the mainland is located, for example, North America is in the northern hemisphere, and Africa crosses the equator. Describe it in as much detail as possible.

Carefully study the coordinate grid and find the coordinates of the mainland: the northernmost (upper), southern (lower), western (right) and eastern (left) points. To find the coordinates of a point, find the latitude and longitude.

Latitude is measured from the equator, if you go up from the equator, then the latitude value will be positive, if you go down - negative. It is impossible to determine the exact value on paper, estimate approximately according to the drawn parallels (horizontal lines). That is, if your point (for example, Cape Agulhas - the southernmost point in Africa) lies between the parallels 30 ° and 45 °, divide this distance by an eye and determine about 34 ° - 35 °. For a more accurate definition, use an electronic map or geographical atlases.

Longitude is measured from the prime meridian (this is a line passing through London). If your point lies to the east of this line, put a "+" in front of the value, if to the west, put a "-". In the same way as latitude, determine longitude, only not along horizontal, but along vertical lines (meridians). The exact value can only be found on an electronic map or with the help of a sextant.

Record the coordinates of all extreme points of the mainland in the form (latitude from -90° to +90°, from -180° to +180°). For example, the coordinates of Cape Agulhas will be equal to (34.49 ° south latitude and 20.00 ° east longitude). The modern notation of the coordinate system implies notation in degrees and decimal fractions, but measurement in degrees and minutes was popular earlier; you can use either system of notation.

Globes and maps have their own coordinate system. Thanks to this, any object of our planet can be applied and found on them. Geographic coordinates are longitude and latitude, these angular values ​​are measured in degrees. With their help, you can determine the position of an object on the surface of our planet relative to the prime meridian and the equator.

Instruction

Instruction

Determine if a river flows through the mainland. In the northern regions, atmospheric precipitation quickly accumulates into ice, so there are no rivers with a rapid flow. In the south, on the contrary, rain moisture evaporates quickly, so there are no rivers there either. The most full-flowing rivers with fast and stormy currents are observed in the middle part of the country.

Find out where the river flows. All rivers flow into seas or oceans. The junction of the river and the sea is called the mouth.

Determine which direction the river is flowing. There will be no problems with this, since the direction of the flow of rivers is from the source to the mouth.

Also, for a complete geographical study, establish how the river flows (i.e. what kind of current is in it: fast, slow, turbulent flow), depending on the relief.

Determine the type of river. All rivers are divided into mountain and flat. In the mountains, the current is fast, stormy; in the plains it is slow, and the valleys are wide and terraced.

Explain the economic and historical significance of the river. Indeed, throughout the development of mankind, rivers have played a significant role in the development of the area. Since ancient times, they have been used as trade routes, for fish farming and fishing, timber rafting, water supply and irrigation of fields. Since ancient times, people settled on the banks of rivers. Now the river is the main source of hydroelectric power and the most important transport route.

Related videos

What is tundra?

The natural zone is located in the northern hemisphere and covers the northern part of Russia and Canada. The nature here is very scarce, and the climate is considered harsh. Summer is practically absent - it lasts only a few weeks, and the temperature, as a rule, is kept at the level of 10-15 degrees Celsius. Precipitation is frequent, but the total amount is small.

The tundra stretches along the entire coast of the Arctic Ocean. Due to constant low temperatures, winter here lasts for about nine months (the temperature can be up to -50°C), and the rest of the time the temperature does not rise above +15°C. Low temperatures also lead to the fact that the earth is frozen all the time and does not have time to thaw.

There are no forests and tall trees here. In this area there are only marshes, small streams, mosses, lichens, low plants and shrubs that can survive in such a harsh climate. Their flexible stems and low height allow them to adapt to cold winds.
However, the tundra is still a beautiful place. This can be especially noticed in summer, when it sparkles with different colors due to the many delicious berries that spread like a beautiful carpet.

In addition to berries and mushrooms, herds of reindeer can be found in the tundra in summer. At this time of the year, they feed on everything they find: lichens, leaves, etc. And in winter, deer feed on plants that they get out from under the snow, while they can even break it with their hooves. These animals are very sensitive, have a great charm, and also know how to swim - reindeer can freely swim across a river or lake.

Flora and fauna

The flora in the tundra is very poor. The soil of this zone can hardly be called fertile, since most of the time it is frozen. Few plant species can survive in such difficult conditions, where there is little heat and sunlight. Mosses, lichens, snow buttercups, saxifrages grow here, and some berries appear in summer. All plants here are of dwarf growth. The "forest", as a rule, grows only up to the knee, and the local "trees" are no taller than an ordinary mushroom. The geographical position is completely unsuitable for forests, since the temperature here has been low for many years in a row.

As for animals, the tundra is most suitable for those who prefer the sea. Due to the large amount of water in these places, many waterfowl live here - ducks, geese, loons. The fauna of the tundra is rich in hares, foxes, wolves, brown and

The northernmost point of Africa

A closer examination of the characteristics of this point shows that it is a cape, protruding far enough into the Mediterranean Sea. The Arabic name of this world-famous point is pronounced as "Ras al-Abyad", but quite often you can find an abbreviated version of this phrase - "El-Abyad".

From a substantive point of view, both of these options are legitimate. The fact is that "ras" in translation from Arabic into Russian just means "cape", so the use of the Russian counterpart in this situation is quite acceptable. In turn, the word "abyad" can be translated from the original language as "white", and "al" is just an untranslatable article in this situation. Thus, the name of the extreme northern point of Africa, translated into Russian, means "white cape".

Nevertheless, according to geographers, it is unlikely that this name was given to it in connection with its northern position. Most likely, this name reflects the special color of the sand on this Mediterranean coast.

Other names

Another name common in those days was the name "Ras Engel", which, by analogy with the modern name, was often shortened to the version of "Engela": in fact, such a name can be translated into modern Russian as "Cape Engel". Researchers suggest that this African cape could have received the name in honor of the German traveler Franz Engel, who was quite famous in his time, who made several significant geographical discoveries at the turn of the 19th-20th centuries, although his activity was more connected with South America than with Africa .

Good day!

Almost every one of us has found ourselves in a situation where you wander into an unfamiliar part of the city and try to find the right address. Now, of course, technology has stepped forward and a regular smartphone allows you to navigate the terrain great...

However, far from everywhere and not everything is drawn on Google and Yandex maps. Not so long ago, I was in a new part of my city, and, as it turned out, some streets of this area are simply not shown on the map. How can you tell another person where you are and how to find you?

Actually, this short note is devoted to coordinates and finding a specific point on the map using map services from Yandex and Google. So...

How to determine your coordinates and how to find an address by coordinates

I'll start with Google maps, the official site :

To accurately determine your coordinates - click on the "Location determination" button, usually a small window immediately pops up in the browser asking whether to allow access (select "Allow").

Important! By the way, in some cases, different services can show you in "different places". Therefore, double-check your coordinates on 2 maps at once.

If the street is long, and there are no house numbers (or, in Google maps, houses in this territory are not indicated at all) - then left-click on the point next to the one determined by Google - a small tab should pop up below, in which your coordinates!

Coordinates represent out of two numbers. For example, on the screen below, these are: 54.989192 and 73.319559

Knowing these numbers, you can transfer your location to anyone (even if he does not use Google maps, which is very convenient).

To find the desired point in Google by coordinates, just open the maps and enter these two numbers in the search box (upper left): after 1-2 seconds. a red flag will light up on the maps, indicating the desired point.

Note:

1. coordinates must be specified through a dot, not a comma (correct: 54.989192 73.319559; incorrect: 54.989192 and 73.319559);
2. indicate the coordinates in the order in which their map gives you: i.e. first latitude, then longitude (if you violate the order, you will get the wrong point at all, perhaps even 1000 km further than the desired one ...);
3. coordinates can be specified in degrees and minutes (example: 51°54" 73°31").

Yandex maps

By and large, with Yandex-maps, the principle of operation is similar. It is worth noting that if one service does not determine the address, try using another one. Sometimes, if a street or district is not drawn in Google maps, then in Yandex, on the contrary, it is displayed quite fully, all streets are signed, and you can easily find out where to go and what to do.

Yandex Maps also has a special. a tool that allows you to find out your location online (on the right, click on the arrow in the white circle, see the screen below).

To determine the coordinates - just click on the necessary points on the map - a small window will pop up with addresses and two numbers - that's what they are.

You can insert both a specific address and coordinates into the search string (do not forget that they must be set correctly: do not confuse the sequence, specify through a dot, not a comma!).

Addition!

I have another article of a similar nature on my blog - about determining distances between cities, choosing the best road and estimating travel time. It will be useful to everyone who is going to go to another city, I recommend:

Additions are welcome...

In Chapter 1, it was noted that the Earth has the shape of a spheroid, that is, an oblate ball. Since the terrestrial 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 an 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) is the pole opposite to the north.
If we mentally cut the globe with a plane passing through the axis (parallel to the axis) of the Earth's rotation, we get an imaginary plane, which is called meridian plane . The line of intersection of this plane with the earth's surface is called geographic (or true) meridian .
The plane perpendicular to the earth's axis and passing through the center of the earth is called equatorial plane , and the line of intersection of this plane with the earth's surface - equator .
If you mentally cross the globe with planes parallel to the equator, then circles are obtained on the surface of the Earth, which are called parallels .
Parallels and meridians plotted on globes and maps make up degree grid (Fig. 3.1). The degree grid makes it possible to determine the position of any point on the earth's surface.
For the initial meridian in the preparation of topographic maps taken 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 Hirstmonceau Castle 102.5 meters (5.31 seconds) east of the Greenwich Astronomical Meridian. The 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 by 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 a point relative to the earth's equator and one of the meridians, taken as the initial one. Geographic coordinates may be derived from astronomical observations or geodetic measurements. In the first case they are called astronomical , in the second - geodetic . For astronomical observations, the projection of points onto the surface is carried out by plumb lines, for geodetic measurements - by normals, therefore the values ​​of astronomical and geodetic geographical coordinates are somewhat different. To create small-scale geographical 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 - angular value that determines the position of a point on Earth in the direction from the equator (0º) to the North Pole (+90º) or South Pole (-90º). Latitude is measured by the central angle in the meridian plane of a given point. On globes and maps, latitude is shown using parallels.

Rice. 3.2. Geographic latitude

Longitude - 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 called the angular quantities (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 initial meridian.

spherical latitude (φ) call 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) is the angle between the zero meridian plane and the meridian plane of the given point (the plane passes through the given point and the axis of rotation).

Rice. 3.4. Geographic spherical coordinate system

In the practice of topography, a sphere with a radius R = 6371 is used km, whose surface 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 geographical coordinates are latitude and longitude, which 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) called 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 axis of rotation of the Earth.
astronomical meridian - the line of intersection of the surface of the geoid with the plane of the astronomical meridian.

Astronomical longitude (λ) called 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

AT geodetic geographic coordinate system for the surface on which the positions of the points are found, the surface is taken reference -ellipsoid . The position of a point on the surface of the reference ellipsoid is determined by two angular values ​​- the geodetic latitude (AT) and geodetic longitude (L).
Plane of the geodesic meridian - 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 an ellipsoid by a plane passing through a given point and perpendicular to the minor axis.

Geodetic latitude (AT)- 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 the given point and the plane of the initial geodesic meridian.

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

3.2. DETERMINATION OF 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 the meridians, and the upper and lower frames are the parallels. . (Fig. 3.7). Consequently, geographic coordinates can be determined by the side frames of the topographic map . On all maps, the top frame always faces north.
Geographic latitude and longitude are signed in the corners of each sheet of the map. On maps of the Western Hemisphere, in the northwestern corner of the frame of each sheet, to the right of the longitude of the meridian, 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 through one and divided by dots (except for the 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 frames of the card

When compiling 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, respectively, through 20′ and 40 "(minutes), and meridians - through 30" and 1 °.
The geographical 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 with a scale of 1: 50,000 "ZAGORYANI", the nearest parallel located to the south of a given point will be the parallel 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 must:

• set one leg of the measuring compass to a given point, set the other leg along the shortest distance to the nearest parallel (for our map 54º40 ′);
• without changing the solution of the measuring compass, install it on the side frame with minute and second divisions, one leg should be on the south 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 south parallel to the second leg of the measuring compass;
• add the result obtained to the south latitude (for our map 54º40 ′).

To determine the longitude of a given point, you must:

• set one leg of the measuring compass to a given point, set the other leg along the shortest distance to the nearest meridian (for our map 18º00′);
• without changing the solution of the measuring compass, set it to 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 at a scale of 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 side. Therefore, the discrepancies between the measurements of longitude on the northern and southern frames may differ by several seconds. To achieve high accuracy in the measurement results, it is necessary to determine the longitude on both the south and north sides of the frame, and then interpolate.
To improve the accuracy of determining geographic coordinates, you can use graphic method. To do this, it is necessary to connect with straight lines the ten-second divisions of the same name nearest to the point in latitude south of the point and in longitude west of it. Then determine the dimensions of the segments in latitude and longitude from the drawn lines to the position of the point and summarize them, respectively, with the latitude and longitude of the drawn lines.
The accuracy of determining geographical coordinates on maps of scales 1: 25,000 - 1: 200,000 is 2" and 10", respectively.

3.3. POLAR COORDINATE SYSTEM

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

The 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 - the projection of the terrain line on 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

For the polar axis can be taken: the true meridian, the magnetic meridian, the vertical line of the grid, the direction to any landmark.

3.2. BIPOLAR COORDINATE SYSTEMS

Bipolar coordinates call two angular or two linear quantities that determine the location of a point on a plane relative to two starting points (poles O 1 and O 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

Previously reviewed plan coordinate systems , defining the position of any point on the surface of the earth's ellipsoid, or the reference ellipsoid , or on the plane. However, these planned coordinate systems do not allow obtaining an unambiguous position of a point on the physical surface of the Earth. Geographic coordinates refer the position of the point to the surface of the reference ellipsoid, polar and bipolar coordinates refer the position of the point to the plane. And all these definitions have nothing to do with the physical surface of the Earth, which is more interesting for the geographer than the reference ellipsoid.
Thus, the planned 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”, “below”. Just about what? To obtain complete information about the position of a point on the physical surface of the Earth, the third coordinate is used - height . Therefore, it becomes necessary to consider the third coordinate system - height system .

The distance along a plumb line from the 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 level of the ocean or the open sea in a calm state is taken as the origin of absolute heights. In Russia and Ukraine, the absolute heights are taken as the origin 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, which is 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 footstock was installed during the reign of Peter the Great, and since 1703 regular observations of the level of the Baltic Sea began. Soon the footstock was destroyed, and only from 1825 (and up to the present time) regular observations were resumed. In 1840, hydrographer M.F. Reinecke calculated the average height of the Baltic Sea and recorded it on the granite abutment of the bridge in the form of a deep horizontal line. Since 1872, this feature has been taken as a zero mark when calculating the heights of all points on the territory of the Russian state. The Kronstadt footstock was repeatedly modified, however, the position of its main mark was kept the same during design changes, i.e. determined in 1840
After the collapse of the Soviet Union, Ukrainian surveyors did not begin to invent their own national system of heights, and at present, Ukraine still uses 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 system of heights. These points are called benchmarks .
Absolute heights H can be positive (for points above the Baltic Sea level) and negative (for points below the Baltic Sea level).
The difference between the absolute heights of two points is called relative tall or excess (h):
h = H BUT-H AT .
The excess of one point over another can also be positive and negative. If the absolute height of the point BUT greater than the absolute height of the point AT, i.e. is above the point AT, then the excess of the point BUT over the dot AT will be positive, and vice versa, exceeding the point AT over the dot BUT- negative.

Example. Absolute heights of points BUT and AT: H BUT = +124,78 m; H AT = +87,45 m. Find Mutual Exceedances of Points BUT and AT.

Solution. Exceeding point BUT over the dot AT
h A(B) = +124,78 - (+87,45) = +37,33 m.
Exceeding point AT over the dot BUT
h B(A) = +87,45 - (+124,78) = -37,33 m.

Example. Point absolute height BUT is equal to H BUT = +124,78 m. Exceeding point FROM over the dot BUT equals h C(A) = -165,06 m. Find the absolute height of a point FROM.

Solution. Point absolute height FROM is equal to
H FROM = H BUT + h C(A) = +124,78 + (-165,06) = - 40,28 m.

The numerical value of the height is called the elevation of the point (absolute or conditional).
For example, H BUT = 528.752 m - absolute mark of the point BUT; H" AT \u003d 28.752 m - conditional elevation of the point AT .

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

To move from conditional to absolute heights and vice versa, it is necessary 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 coordinates?
4. Using the drawing, expand 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 the drawing, expand the concepts of "astronomical latitude" and "astronomical longitude".
7. On what surface is the position of points in the geodetic coordinate system determined?
8. Using the drawing, expand the concepts of "geodesic latitude" and "geodesic longitude".
9. Why is it necessary to connect ten-second divisions of the same name closest to the point with straight lines to improve the accuracy of determining longitude?
10. How can you calculate the latitude of a point if you determine the number of minutes and seconds from the northern frame of a topographic map?
11. What are the polar coordinates?
12. What is the purpose of the polar axis in a polar coordinate system?
13. What coordinates are called bipolar?
14. What is the essence of the direct geodetic problem?

Globes and maps have a coordinate system. With its help, you can put 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 - the angle between a plumb line at a particular point and the plane of the equator (zero parallel). Latitude in the Southern Hemisphere is called South, while in the Northern Hemisphere it is called North. It can vary from 0 ∗ to 90 ∗ .

Geographic longitude is the angle that is made by the meridian plane at a certain point to the prime meridian plane. If the longitude reading goes east from the initial Greenwich meridian, then it will be eastern longitude, and if it goes west, then it will be western longitude. Longitude values ​​can be from 0 ∗ to 180 ∗ . Most often, on globes and maps, meridians (longitude) are indicated at their intersection with the equator.

How to determine your coordinates

When a person gets into an emergency situation, he must, first of all, be well oriented on the ground. In some cases, it is necessary to have certain skills in determining the geographical coordinates of your location, for example, in order to transfer them to rescuers. There are several ways to do this the handy way. We present the simplest of them.

Determining longitude with a gnomon

If you are traveling, it is best to set your watch to Greenwich Mean Time:

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

Calculations are made based on the following:

• since the Earth makes a complete revolution in 24 hours, therefore, 15 ∗ (degrees) it will pass 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 is before 12 noon GMT, you are in the Eastern Hemisphere;
• if you spotted 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 11:36, 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.

• The thread with the 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.
• From the indicators of the angle between the plumb line of the protractor and its base, 90 ∗ is subtracted. The result is the angle between the horizon and the 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 currently located.

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, zoomed in and out with the mouse wheel
  • Find a place by name using the search.
• Click on the desired location with the right mouse button. Select the desired item from the menu that opens. In this case, "What's in there?" Geographic coordinates will appear in the search line at the top of the window. For example: Sochi - 43.596306, 39.7229. They indicate the geographical latitude and longitude of the center of this city. So you can determine the coordinates of your street or house.

By the same coordinates, you can see the place on the map. You can't just change these numbers. If you put longitude first and then latitude, you run the risk of being in a different place. For example, instead of Moscow, you will end up in Turkmenistan.

How to determine the coordinates on the map

To determine the geographic latitude of an object, you need to find the nearest parallel to it from the side of 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 counted from the 50th parallel to the desired object. This number is equal to 6. Therefore, 50 + 6 = 56. Moscow lies on the 56th parallel.

To determine the geographic longitude of an object, find the meridian where it is located. For example, St. Petersburg lies to the east of Greenwich. Meridian, this one is separated from the zero meridian by 30 ∗ . 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 closer to Greenwich is determined. Then, to this value, it is necessary to add such a number of degrees that is the distance between the object and the meridian closest to Greenwich on the arc of the parallel.

Example, Moscow is located east of the meridian 30 ∗ . Between him and Moscow, the arc of the parallel is 8 ∗ . This means that Moscow has east 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 by an average of 70 m. Parallels and meridians on topographic maps are the inner borders of sheets. Their latitude and longitude are written in the corner of each sheet. Sheets of maps of the Western Hemisphere are marked in the northwest corner of the frame "West of Greenwich". On the maps of the Eastern Hemisphere, respectively, there will be a note "East of Greenwich."