How to determine the geographic coordinates of a point on a map. Geographic latitude and geographic longitude. Geographical coordinates. Determination of geographical coordinates

Latitude- the angle between the local zenith direction and the equatorial plane, measured from 0 to 90 on both sides of the equator. The geographic latitude of points lying in the northern hemisphere (northern latitude) is usually considered positive, the latitude of points in the southern hemisphere - negative. In addition, it is customary to talk about latitudes that are larger in absolute value - as high, and about those close to zero (that is, to the equator) - as about low.

Longitude

Longitude- the angle between the plane of the meridian passing through a given point and the plane of the initial prime meridian, from which longitude is calculated. Now on Earth the prime meridian is the one that passes through the old observatory in the city of Greenwich, and therefore it is called the Greenwich meridian. Longitudes from 0 to 180° east of the prime meridian are called eastern, and to the west - western. Eastern longitudes are considered to be positive, western longitudes are considered negative. It should be emphasized that, unlike latitude, for a system of longitudes the choice of the origin (prime meridian) is arbitrary and depends only on agreement. So, in addition to Greenwich, the meridians of the observatories of Paris, Cadiz, Pulkovo (on the territory of the Russian Empire), etc. were previously chosen as the zero meridians.

Height

To completely determine the position of a point in three-dimensional space, a third coordinate is needed - height. The distance to the center of the planet is not used in geography: it is convenient only when describing very deep regions of the planet or, on the contrary, when calculating orbits in space.

Within the geographical envelope it is usually used height above sea level, measured from the level of the “smoothed” surface - geoid. Such a three-coordinate system turns out to be orthogonal, which simplifies a number of calculations. Altitude above sea level is also convenient because it is related to atmospheric pressure.

Distance from the earth's surface (up or down) is often used to describe a place, however Not serves coordinate due to the unevenness of the surface.

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 northwestern corner of the frame of each sheet, to the right of the meridian longitude value, 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. 3.10. Determining the location of a point from two angles (α 1 and α 2 )

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? To obtain complete information about the position of a point on the physical surface of the Earth, a 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 level of the ocean or open sea in a calm state is taken as the starting point for absolute heights. 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 of the Baltic Sea began. 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 of the 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 collapse of the Soviet Union, Ukrainian surveyors did not invent their own national system of heights, 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

Expand the concepts: pole, equatorial plane, equator, meridian plane, meridian, parallel, degree grid, coordinates.
Relative to what planes on the globe (ellipsoid of revolution) are geographic coordinates determined?
What is the difference between astronomical geographic coordinates and geodetic ones?
Using a drawing, explain the concepts of “spherical latitude” and “spherical longitude”.
On what surface is the position of points in the astronomical coordinate system determined?
Using a drawing, explain the concepts of “astronomical latitude” and “astronomical longitude”.
On what surface are the positions of points determined in a geodetic coordinate system?
Using a drawing, explain the concepts of “geodetic latitude” and “geodetic longitude”.
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?
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?
What coordinates are called polar?
What purpose does the polar axis serve in a polar coordinate system?
What coordinates are called bipolar?
What is the essence of the direct geodetic problem?

Each point on the planet's surface has a specific position, which corresponds to its own latitude and longitude coordinates. It is located at the intersection of the spherical arcs of the meridian, which corresponds to longitude, with the parallel, which corresponds to latitude. It is denoted by a pair of angular quantities expressed in degrees, minutes, seconds, which has the definition of a coordinate system.

Latitude and longitude are the geographic aspect of a plane or sphere translated into topographic images. To more accurately locate a point, its altitude above sea level is also taken into account, which makes it possible to find it in three-dimensional space.

Latitude and longitude

The need to find a point using latitude and longitude coordinates arises due to the duty and occupation of rescuers, geologists, military personnel, sailors, archaeologists, pilots and drivers, but it may also be necessary for tourists, travelers, seekers, and researchers.

What is latitude and how to find it

Latitude is the distance from an object to the equator line. Measured in angular units (such as degrees, degrees, minutes, seconds, etc.). Latitude on a map or globe is indicated by horizontal parallels - lines that describe a circle parallel to the equator and converge in the form of a series of tapering rings towards the poles.

Lines of latitude

Therefore, they distinguish between northern latitude - this is the entire part of the earth's surface north of the equator, and also southern latitude - this is the entire part of the planet's surface south of the equator. The equator is the zero, longest parallel.

Parallels from the equator line to the north pole are considered to be a positive value from 0° to 90°, where 0° is the equator itself, and 90° is the top of the north pole. They are counted as northern latitude (N).
Parallels extending from the equator towards the south pole are indicated by a negative value from 0° to -90°, where -90° is the location of the south pole. They are counted as southern latitude (S).
On the globe, parallels are depicted as circles encircling the ball, which become smaller as they approach the poles.
All points on the same parallel will be designated by the same latitude, but different longitudes.
On maps, based on their scale, parallels have the form of horizontal, curved stripes - the smaller the scale, the straighter the parallel strip is depicted, and the larger it is, the more curved it is.

Remember! The closer to the equator a given area is located, the smaller its latitude will be.

What is longitude and how to find it

Longitude is the amount by which the position of a given area is removed relative to Greenwich, that is, the prime meridian.

Lines of longitude

Longitude is similarly characterized by measurement in angular units, only from 0° to 180° and with a prefix - eastern or western.

The Greenwich Prime Meridian vertically encircles the globe of the Earth, passing through both poles, dividing it into the western and eastern hemispheres.
Each of the parts located west of Greenwich (in the Western Hemisphere) will be designated west longitude (w.l.).
Each of the parts distant from Greenwich to the east and located in the eastern hemisphere will bear the designation east longitude (E.L.).
Finding each point along one meridian has the same longitude, but different latitude.
Meridians are drawn on maps in the form of vertical stripes curved in the shape of an arc. The smaller the map scale, the straighter the meridian strip will be.

How to find the coordinates of a given point on the map

Often you have to find out the coordinates of a point that is located on the map in a square between the two nearest parallels and meridians. Approximate data can be obtained by eye by sequentially estimating the step in degrees between the mapped lines in the area of interest, and then comparing the distance from them to the desired area. For accurate calculations you will need a pencil with a ruler, or a compass.

For the initial data we take the designations of the parallels closest to our point with the meridian.
Next, we look at the step between their stripes in degrees.
Then we look at the size of their step on the map in cm.
We measure with a ruler in cm the distance from a given point to the nearest parallel, as well as the distance between this line and the neighboring one, convert it to degrees and take into account the difference - subtracting from the larger one, or adding to the smaller one.
This gives us the latitude.

Example! The distance between the parallels 40° and 50°, among which our area is located, is 2 cm or 20 mm, and the step between them is 10°. Accordingly, 1° is equal to 2 mm. Our point is 0.5 cm or 5 mm away from the fortieth parallel. We find the degrees to our area 5/2 = 2.5°, which must be added to the value of the nearest parallel: 40° + 2.5° = 42.5° - this is our northern latitude of the given point. In the southern hemisphere, the calculations are similar, but the result has a negative sign.

Similarly, we find longitude - if the nearest meridian is further from Greenwich, and the given point is closer, then we subtract the difference, if the meridian is closer to Greenwich, and the point is further, then we add it.

If you only have a compass at hand, then each of the segments is fixed with its tips, and the spread is transferred to the scale.

In a similar way, calculations of coordinates on the surface of the globe are carried out.

The best services for finding a place by coordinates

The easiest way to find out your location is by logging into the PC version of the service, which works directly with Google Maps. Many utilities make it easy to enter latitude and longitude in a browser. Let's look at the best of them.

Map & Directions

In addition, Maps & Directions allows you to determine the coordinates of your position on the map for free by clicking just one button. Click on “Find my coordinates”, and the service will immediately place a marker and determine the latitude, longitude to many thousandths, as well as altitude.

On the same site you can measure the distance between settlements or the area of any given territory, draw a route or calculate travel time. The service will be useful for both travelers and simply curious users.

Mapcoordinates.net

A useful utility, Mapcoordinates.net, allows you to find out the coordinates of a point in any region of the world. The service is also integrated with Google Maps, but has a simplified interface, thanks to which even an untrained user can use it.

In the address bar of the utility, where it says “Search,” enter the address of the place, latitude and longitude of which you want to get. A map with coordinates will appear along with a marker at the desired location. The latitude, longitude, and altitude of the selected point will be displayed above the marker.

Unfortunately, Mapcoordinates.net is not suitable for searching for points knowing their coordinates. However, for the reverse procedure, this is a very convenient utility. The service supports many languages, including Russian.

Search by coordinates on the map through a browser using the Google Maps service

If for some reason you prefer to work not with simplified services, but directly with Google Maps, then these instructions will be useful for you. The process of searching by coordinates through Google Maps is a little more complicated than in the methods described earlier, but it can be mastered quickly and without much difficulty.

To find out the exact coordinates of a place, follow these simple instructions:

Open the service on your PC. It is important that the full mode must be turned on, and not the light mode (marked with a special lightning icon), otherwise it will not be possible to obtain information;

Click on the section of the map where the item or point you need is located, with the right mouse button;

Select the “What’s here?” option in the menu that appears;

Look at the tab that appears at the bottom of the screen. It will display latitude, longitude and altitude.

To determine a location using known geographic coordinates, a different procedure will be required:

Press the “Enter” key, and a special marker will appear on the map at the required location.

The most important thing when using the Google Maps service is to correctly indicate geographic coordinates. Cards only recognize a few data formats, so be sure to keep the following input rules in mind:

When entering degrees, use the special character to indicate it as "°" rather than "d";

You must use a dot rather than a comma as a separator between the integer and fractional parts, otherwise the search string will not be able to return the location;

Latitude is indicated first, then longitude. The first parameter must be written in the range from -90 to 90, the second - from -180 to 180.

Finding a special character on a PC keyboard is difficult, and in order to adhere to the required list of rules, you need to put in a lot of effort. It is much easier to use special utilities - we have listed the best of them in the section above.

Finding a place by latitude and longitude on Android OS

Often you need to find a place by coordinates far from your laptop or personal computer. The Google Maps mobile application running on the Android platform will help out. It is usually used to get directions or find out vehicle schedules, but the program is also suitable for finding the location of a point or point.

You can download the application for Android on the official page on Google Play. It is available in both Russian and English. After installing the program, follow the following instructions.

Geographic latitude and longitude are plotted on a world map. With their help, it is easy to determine the location of an object.

A geographical map of the world is a reduced projection of the earth's surface on a plane. It shows continents, islands, oceans, seas, rivers, as well as countries, large cities and other objects.

The geographical map has a coordinate grid.
On it you can clearly see information about the continents, seas and oceans, and the map allows you to create an image of the relief of the world.
Using a geographic map, you can calculate the distance between cities and countries. It is also convenient to search for the location of land and ocean objects.

The shape of the Earth is like a sphere. If you need to determine a point on the surface of this sphere, then you can use a globe, which is our planet in miniature. But there is the most common way to find a point on Earth - these are geographical coordinates - latitude and longitude. These parallels are measured in degrees.

Geographic map of the world with latitude and longitude - photo:

The parallels that are drawn along and across the entire map are latitude and longitude. With their help you can quickly and easily find anywhere in the world.

The geographical map of the hemispheres is easy to understand. On one hemisphere (eastern) Africa, Eurasia and Australia are depicted. On the other, the western hemisphere, are North and South America.

Our ancestors studied latitude and longitude. Even then there were world maps that were not similar to modern ones, but with their help you can also determine where an object is located and what. A simple explanation of what the geographic latitude and longitude of an object on a map are:

Latitude is a coordinate value in the system of spherical numbers, which defines a point on the surface of our planet relative to the equator.

If objects are located in the northern hemisphere, then the geographic latitude is called positive, if in the southern hemisphere - negative.
South latitude - the object moves from the equator towards the North Pole.
North latitude - the object is moving towards the South Pole from the equator.
On a map, latitudes are lines parallel to each other. The distance between these lines is measured in degrees, minutes, seconds. One degree is 60 minutes, and one minute is 60 seconds.
The equator is zero latitude.

Longitude is a coordinate quantity that determines the location of an object relative to the prime meridian.

This coordinate allows you to find out the location of the object relative to the west and east.
Lines of longitude are meridians. They are located perpendicular to the equator.
The zero reference point for longitude in geography is the Greenwich Laboratory, which is located in east London. This line of longitude is commonly called the Greenwich meridian.
Objects that are located to the east of the Greenwich meridian are the eastern longitude region, and to the west are the western longitude region.
Indicators of eastern longitude are considered positive, and indicators of western longitude are considered negative.

Using the meridian, a direction such as north-south is determined, and vice versa.

Latitude on a geographic map is measured from the equator—zero degrees. At the poles there are 90 degrees of latitude.

From what points, what meridian is geographic longitude measured?

Longitude on a geographic map is measured from Greenwich. The prime meridian is 0°. The farther an object is from Greenwich, the greater its longitude.

To determine the location of an object, you need to know its geographic latitude and longitude. As mentioned above, latitude shows the distance from the equator to a given object, and longitude shows the distance from Greenwich to the desired object or point.

How to measure, find out geographic latitude and longitude on a world map? Each parallel of latitude is designated by a specific number - a degree.

Meridians are also designated by degrees.

Measure, find out geographic latitude and longitude on a world map

Any point will be located either at the intersection of the meridian and the parallel, or at the intersection of intermediate indicators. Therefore, its coordinates are indicated by specific indicators of latitude and longitude. For example, St. Petersburg is located at the following coordinates: 60° north latitude and 30° east longitude.

As stated above, latitude is parallels. To determine it, you need to draw a line parallel to the equator or a nearby parallel.

If the object is located on the parallel itself, then it is easy to determine its location (as described above).
If an object is between parallels, then its latitude is determined by the nearest parallel from the equator.
For example, Moscow is located north of the 50th parallel. The distance to this object is measured along the meridian and it is equal to 6°, which means that Moscow’s geographic latitude is 56°.

A clear example of determining geographic latitude coordinates on a world map can be found in the following video:

Video: Geographic latitude and geographic longitude. Geographical coordinates

To determine geographic longitude, you need to determine the meridian on which the point is located, or its intermediate value.

For example, St. Petersburg is located on a meridian whose value is 30°.
But what if the object is located between the meridians? How to determine its longitude?
For example, Moscow is located east of 30° east longitude.
Now add the number of degrees along the parallel to this meridian. It turns out 8° - which means the geographic longitude of Moscow is equal to 38° east longitude.

Another example of determining the geographic coordinates of longitude and latitude on a world map in the video:

Video: Determining latitude and longitude

Any map shows all the parallels and meridians. What is the maximum value of geographic latitude and longitude? The greatest value of geographic latitude is 90°, and longitude is 180°. The smallest latitude value is 0° (equator), and the smallest longitude value is also 0° (Greenwich).

Geographic latitude and longitude of the poles and the equator: what is it equal to?

The geographic latitude of the points of the earth's equator is 0°, the North Pole +90°, and the South Pole -90°. The longitude of the poles is not determined, since these objects are located on all meridians at once.

Determining geographic coordinates of latitude and longitude on Yandex and Google maps online

Students may need to determine geographic coordinates from maps in real time when taking a test or exam.

It's convenient, fast and simple. Determining the geographic coordinates of latitude and longitude on Yandex and Google maps online can be done on various services on the Internet.
For example, you just need to enter the name of an object, city or country and click on it on the map. The geographic coordinates of this object will instantly appear.
In addition, the resource will show the address of the identified point.

The online mode is convenient because you can find out the necessary information here and now.

How to find a place by coordinates on Yandex and Google map?

If you do not know the exact address of an object, but you know its geographical coordinates, then its location can be easily found on Google or Yandex maps. How to find a place by coordinates on Yandex and Google map? Follow these steps:

For example, go to Google map.
Enter the geographic coordinates in the search box. You can enter degrees, minutes and seconds (for example 41°24’12.2″N 2°10’26.5″E), degrees and decimal minutes (41 24.2028, 2 10.4418), decimal degrees: (41.40338, 2.17403).
Click “Search” and the desired object on the map will appear in front of you.

The result will appear instantly, and the object itself will be marked on the map with a “red drop”.

Finding satellite maps with latitude and longitude coordinates is easy. You only need to enter keywords into the Yandex or Google search window, and the service will instantly return what you need.

For example, “Satellite maps with latitude and longitude coordinates.” Many sites will open providing such a service. Choose any one, click on the desired object and determine the coordinates.

Satellite maps - determining latitude and longitude coordinates

The Internet gives us great opportunities. If previously you only had to use a paper map to determine longitude and latitude, now it is enough to have a gadget with a network connection.

Video: Geographic coordinates and coordinate determination

The concept of geographic coordinates (latitude and longitude) is information recorded in a special way about the correctly defined position of an object on the earth’s surface in the format accepted in a given coordinate system.

To solve most practical problems, the surface of the planet can be taken as a plane, where the location of a point is characterized by only two coordinates. In modern geography, such coordinates are called latitude and longitude of a point. To a first approximation, these properties of a point can be represented in the form of the distance by which it is separated from the initial value of latitude and longitude.

To correlate the position of an object with the real world, a model of the Earth was created in the form of a map with geographic objects depicted on it: continents, mountains, rivers, cities, etc. A degree grid is applied over these objects, which serves to determine the coordinates of any place of interest.

How to determine latitude and longitude? There are several ways.

Depending on the goals set for the map compilers, the coordinate system may be different. In this case, the model of the Earth can be taken either as an ideal sphere or as a special geometric figure - the geoid.

Spherical coordinates

If the map represents only a small part of the earth's surface and has a small scale, then a spherical coordinate system is used when constructing it.

In this system, from a point considered on the surface of the planet to the geometric center of the sphere, a line is drawn perpendicular to its surface, which is called the normal to the point. The angle between this normal and the equatorial plane will be the latitude of the point of interest.

There is also a spherical coordinate system for points above or below the surface. In this case, the normal turns into a third coordinate, which is the height of the point above sea level. This coordinate system is used to calculate the orbits of near-Earth satellites.

Astronomical coordinates

How to determine the latitude and longitude of a point with great accuracy is a task that becomes increasingly difficult as the scale increases. The fact is that the discrepancies between the real shape of the Earth and its spherical model appear much more clearly on finely scaled maps. For such cases, an astronomical coordinate system is used that takes into account the real shape of the planet.

Due to the fact that the planet rotates at a fairly high speed, its internal substance in the form of a liquid mantle experiences centrifugal force. It stretches the planet at the equator and tightens it at the poles. Therefore, the radius of the Earth at these 2 points is different: 6357 km from the center of the planet to the pole and 6378 km from the center to the equator.

This geometric figure is called a geoid. All points on the surface of the geoid are directed not towards its geometric center, but towards its center of mass.

This is the main difference between the astronomical coordinate system and the spherical one. In the first, a line - which in this system is called a plumb line - from a point is parallel to the direction of gravity and perpendicular to the earth's surface, and in the second - to the center of the planet.

To determine the plumb line, astronomical observations of the celestial sphere using special instruments or mathematical calculations based on these observations are used. It will be different for each region, since the matter inside the planet is unevenly distributed.

The concept of latitude

If you connect points at equal distances from the pole with a line, you get a parallel. Such parallels can be extended further and further from one pole towards the other. In this case, their length will increase as they move away, since the plane they describe will increase.

At a certain distance, when the parallel is an equal distance from both poles, it will have a maximum length. This parallel is called the equator, and it limits a plane called the equatorial.

The flat dihedral angle between this plane and the parallel on which the object is located is called geographic latitude. The smaller this angle, the closer the point in question is to the equator line. At the equator itself, the geographic latitude will be zero.

Parallels are located on either side of it, and latitude takes a positive or negative value depending on which hemisphere the object is located in.

The concept of longitude

Perpendicular to the parallels, the earth's surface is crossed by other lines called meridians. These arcs also describe a plane in the form of a circle, each of the 2 sides of which is in the opposite hemisphere. The meridian passing through the English city of Greenwich is usually called the “zero” or “reference” meridian.

The flat dihedral angle between this meridian and the one on which the point under study stands is called geographic longitude. The unfolded angle with a value of 180 0 is directly opposite the zero one, on the other side of the planet. To the east of the reference meridian, longitudes take a positive value, and to the west - a negative value. All meridians converge at one point at the poles of the planet.

Measuring distances using a degree grid

To measure distances using a degree grid, you need to know what 1 0 arc corresponds to. The meridians have a constant length throughout their entire length and 1 0 corresponds to approximately 111 km. The only necessary condition that must be met to find out the distance along the meridian is that both objects must be on the same meridian.

Thus, if the distance between objects is 15 0, then the distance between them will be: 5 x 111 = 555 km.

As for parallels, as they move away from the equator, their length decreases and the exact value in kilometers is quite difficult to find out. Therefore, to calculate the distance between objects located on the same parallel, you should be guided by the table below.

Latitude	Distanceie, km
0 0 (equator)	111,3
5 0	110,9
10 0	109,6
15 0	107,6
20 0	104,6
25 0	102,1
30 0	96,5
35 0	91,3
40 0	85,4
45 0	78,8
50 0	71,7
55 0	64,0
60 0	55,8
65 0	47,2
70 0	38,2
75 0	28,9
80 0	19,4
85 0	9,7
90 0 (pole)	0

Geographical degree

How to determine latitude and longitude and with what quantities to express it became an urgent task with the beginning of the era of great geographical discoveries. The first cartographers proposed using degrees to determine geographic coordinates.

This is explained by the fact that latitude and longitude are essentially flat dihedral angles, for the calculation of which the same units of measurement are applicable as in other areas of geometry.

Geographic map of the world with latitude and longitude

The main characteristic that geographic maps have is the scale at which they are drawn. In general, scale is a reduction indicator that shows how many times the object depicted on the map is smaller than the real one. It is written as a mathematical ratio as 1:1000000. The larger the number on the right, the smaller the scale of the map.

Small-scale maps give only a superficial idea of the coordinates of objects on the earth's surface and the error in determining coordinates from them is about 2 0, which in terms of distance gives an error of several tens of kilometers. In addition, there is a certain difficulty in transferring the spherical shape of the Earth onto the flat surface of a paper map.

In order to get around this limitation, the world map is divided into areas limited by meridians at 4 0 and parallels at 6 0. Thus, maps were obtained in the shape of a trapezoid (in geography it is customary to call these maps “squares”) with a scale of 1:1000000. On this scale, 1 cm is equal to 1 km.

Each resulting square bears an alphanumeric designation according to the Latin alphabet from A to V. To avoid confusion, when designating squares belonging to the southern hemisphere, a small Latin letter “s” is placed before their name: from sA to sV.

To further improve the accuracy of the map, each square is divided into another 144 pieces measuring 20 by 30 minutes. They are numbered in order from left to right and top to bottom. On this scale, 1 cm is equal to 1 km. The geographic coordinates of an object, the accuracy of which requires an error of up to several meters, are determined from large-scale topographic maps.

Determining longitude and latitude

Most geographic maps are on a large scale, so not all meridians and parallels are present on them, but only some of them, usually in increments of 5 to 15 0. This is explained by considerations of convenience: otherwise, the dense degree grid would not allow the user to make out the details of the map.

The line dividing the globe into the northern and southern hemispheres is the equator.

Accordingly, any object on the earth's surface has a northern or southern latitude, depending on which side of the equator it is located. It is important to know that the equator line is also the line from which latitude is measured. Typically, latitude values in degrees are located on the prime meridian, which runs from north to south.

The plane, which is bounded by the 0th and one hundred and 180th meridians, divides the planet into 2 hemispheres: eastern and western. Everything located to the right of the 0 meridian (or to the left of the 180 meridian) has east longitude. By analogy, the second hemisphere has western longitude (if you look to the left of the prime meridian and to the right of the 180 meridian).

It is somewhat easier to find the longitude symbol on the map, since its value is indicated on the parallel closest to the equator, or on the equator itself. The 180th meridian is also the official date line. If the map depicts a specific geographic area, then the latitude and longitude values are plotted directly on the degree grid itself.

How to calculate latitude?

The first step is to find out the hemisphere (northern or southern) in which it is located. Then determine the parallels closest to it, between which it is located. Then it all comes down to basic mathematics.

Saint Petersburg

The easiest example of determining the geographic latitude of a place. This city is located in the northern hemisphere at the 60th parallel. Accordingly, its coordinate is 60 0 north latitude.

Moscow

The capital is also located in the northern hemisphere, but between parallels. Therefore, first it is necessary to determine the value of the step with which the latitudes are plotted on the map. For example, if these are 50 and 60 parallels, then the step value is 60 – 50 = 10 degrees, and if it is 40 and 60 parallels, then 60 – 40 = 20 degrees. Now you need to mentally count the number of degrees by which the city is distant from the lower parallel.

In this case, you can rely on the eye, since the accuracy of determining the coordinates on a geographic map is within 2 0. Now that the number of degrees is determined (in the example it is 6 0), it needs to be added to the lower parallel: 50 + 6 = 56 0 north latitude.

Magadan

This method has other options when the desired object is located closer to the more northern parallel. For example, the city of Magadan is located just south of the sixtieth degree and is significantly removed from the southern parallel. In this case, it is much more convenient to calculate the number of degrees precisely from the northern parallel and subtract the measured amount from it: 60 – 1 = 59 0 northern latitude.

Kilimanjaro

The coordinates of objects located geographically in the southern hemisphere are determined in such a way that the degrees are counted from the equator towards the South Pole. Mount Kilimanjaro is located in Africa in the southern hemisphere between the equator and the 10th parallel. It is only three degrees away from the equator. Thus, its coordinate is: 0 + 3 = 3 0 south latitude.

Cape Town

The capital of South Africa is also located at the southern tip of the African continent between 30 and 40 degrees, slightly closer to the first parallel. Its coordinate will be: 30 + 3 = 33 0 south latitude.

How to calculate longitude?

Finding longitude is no different from finding latitude. However, there is a nuance here - you must first determine the hemisphere in which the object is located.

New Orleans

One of the most famous cities in the United States is located in the western hemisphere on the shores of the Gulf of Mexico. It is located almost on the 90th meridian. Degrees in this hemisphere should be counted from the prime meridian in a westerly direction. Thus, the coordinate of New Orleans is 90 0 West longitude.

Los Angeles

The city is also located in the western hemisphere on the Pacific coast between the 120 and 110 meridians.

The further north or south an object is located from the equator, the easier it is to determine its longitude; as you approach the poles, the distance between degrees decreases. Los Angeles is located 2 degrees from the 120 meridian and its coordinate is 120 – 2 = 118 0 west longitude.

Murmansk

This northern port is located to the right of the prime meridian, which means that it is located in the eastern hemisphere. The closest meridians to it are 30 0 and 40 0. The number of degrees from the 30th meridian to Murmansk is 3 and its coordinate: 30 + 3 = 33 0 east longitude.

Maximum coordinate value

The maximum longitude of a geographic feature is 180 0. Since this meridian does not belong to any hemisphere, when recording this coordinate the name of the hemisphere is omitted. If we are talking about the maximum longitude in each hemisphere, then this is 179 0 as the eastern or western longitude, respectively.

Geographic latitude starts from the equator line, which is the zero line that does not belong to any hemisphere, so the minimum latitude value is 0 0 without hemisphere designation.

The parallels that encircle the entire Earth conventionally divide it into 180 degrees from pole to pole. But, since the equator divides the planet into 2 hemispheres, the maximum longitude of the object will be 180/2 = 90 0 north or south latitude.

Pole and equator

How to determine the latitude and longitude of the poles, which are the extreme points on the geographical map of the world, because they have coordinates that are different from the rest on the globe, is discussed below.

Since latitude is inherently the angle between the equator and the desired object, the maximum angle between any of the poles and the equator will be right. It follows that the geographic latitude of the pole is 90 0 regardless of the hemisphere.

The meridians that determine geographic longitude converge at one point at the pole. Therefore, the poles do not have geographic longitude.

Thus, there is only one coordinate at the poles: 90 0 north or south latitude.

Geographic coordinate system

Geographic coordinates are currently calculated in 4 main ways, each with its own degree of accuracy:

Converting the received degrees into minutes and seconds

Since 1 geographical degree in kilometers is a fairly large value, to more accurately determine the location of an object on the map, other units of measurement have been introduced - minutes and seconds. Converting degrees to minutes and seconds will result in the coordinate being a decimal fraction.

In this case, you should be guided by the fact that there are 60 minutes in one degree, and 60 seconds in a minute:

5 0 18′ 25″ = 18 + 25/60 = 18 + 0.417 = 5 0 25.417′.
179 0 59′ 59″ = 59 + 59/60 = 18 + 0.983 = 179 0 59.983′.

If we translate all the coordinates, then there are 3600 seconds in one degree:

5 0 18′ 25″ = 5 + 18/60 + 25/3600 = 5 + 0.78 + 0.00694 = 5.78694 0
179 0 59′ 59″ = 179 + 59/60 + 59/3600 = 5 + 0.983 + 0.0164 = 5.9994 0

Recording geographic coordinates is subject to strict rules that cannot be deviated from, as it is an international system that must be understood anywhere in the world. How to determine latitude and longitude and record geographic coordinates is given below. There are several recording formats, but they all have a common rule: write latitude coordinates first, then longitude.

Recording received coordinates

Recording in the classical form adopted in Russian-language literature is carried out in Russian. In order to separate units of measurement from each other, they are usually denoted by superscripts: degrees with the sign “0”, minutes with the sign “’”, and seconds with the sign “””.

In this case, the names of the hemispheres, as well as latitudes and longitudes, are written abbreviated, only their first letter is written. For example, the coordinates of Moscow: 55°45′21″ n. w. 37°37′04″ E. d. In this format, the words “latitude” and “longitude” are not written at all, and the hemispheres are written according to the first letter of their English version: North (north), South (south), West (west), East (east).

Depending on the type of record, latitude and longitude can also take negative values without indicating the name of the hemisphere: positive are the northern hemisphere for latitude and the eastern hemisphere for longitude. The rest are with a minus sign.

In addition to everything described above, the coordinate record itself exists in several formats:

As a decimal fraction indicating degrees only.
As a decimal showing only degrees and minutes
As a decimal fraction indicating degrees, minutes and seconds.

A record in all these formats of Moscow coordinates will look like this:

55.755831°, 37.617673°
55°45.35′N, 37°37.06′E
55°45′21″N, 37°37′4″E

As you can see from the example, integer values are separated from decimal values by a dot. In order to recalculate coordinates in another format, you need to divide the minutes by 60, and the seconds by 3600, to record only degrees, or multiply to record the full format.

In the vastness of the World Wide Web, there are a huge number of services where this recalculation is automated.

The development of international communication would be impossible without an accurate determination of one’s location (latitude and longitude). In the modern era, this has allowed even ordinary users to confidently navigate their route in unknown areas and not be afraid of getting lost.

Article format: Lozinsky Oleg

Video on how to determine latitude and longitude

Geographic latitude and geographic longitude: