Geographic coordinates - angular values: latitude (p and longitude K, determining the position of objects on earth's surface and on a map, determine the position of a point on the earth’s surface or, more broadly, in the geographic envelope.

Geographic coordinates are constructed according to the spherical principle. Similar coordinates are used on other planets, as well as on celestial sphere Latitude is the angle φ 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 located in the northern hemisphere (northern latitude) is usually considered positive, the latitude of points in the southern hemisphere is considered negative. It is customary to speak of latitudes close to the poles as high, and those close to the equator as low. The length of the day depends on the latitude of the place, as well as on the time of year.

Due to the difference in the shape of the Earth from a sphere, the geographic latitude of points differs somewhat from their geocentric latitude, that is, from the angle between the direction to a given point from the center of the Earth and the plane of the equator.

The latitude of a place can be determined using astronomical instruments such as a sextant or gnomon (direct measurement), you can also use GPS or GLONASS systems (indirect measurement). Longitude is the angle λ between the plane of the meridian passing through a given point and the plane of the initial prime meridian, from whose longitude is measured. 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.

The choice of the prime meridian is arbitrary and depends only on agreement. Now the Greenwich meridian, passing through the observatory in Greenwich, in south-east London, is taken as the prime meridian. Previously, the meridians of the observatories of Paris, Cadiz, Pulkovo, etc. were chosen as the zero meridians. Local time depends on longitude. To completely determine the position of the point 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 geographic envelope, the “height above sea level” is usually used, measured from the level of the “smoothed” surface - the geoid. Such a three-coordinate system turns out to be orthogonal, which simplifies a number of calculations. The altitude above sea level is also convenient because it is associated with atmospheric pressure. Distance from the earth's surface (upward or inward) is often used to describe a place, but does not serve as a coordinate. In navigation, the center of mass is chosen as the origin of the coordinate system vehicle(TS). The transition of the origin of coordinates from the inertial coordinate system to the geographic one (i.e. from O_i to O_g) is carried out based on the values of latitude and longitude. The coordinates of the center of the geographic coordinate system O_g in the inertial one take on the following values (when calculated using a spherical model of the Earth):

X_(og)=(R+h) cos(\varphi) cos(Ut+\lambda) Y_(og)=(R+h) cos(\varphi) sin(Ut+\lambda) Z_(og)=(R+ h) sin(\varphi) where R is the radius of the earth, U is the angular velocity of the earth's rotation, h is the height above sea level. The orientation of the axes in the geographic coordinate system (GCS) is selected according to an algorithm.

The X axis (another designation is the E axis) is the axis directed to the east. The Y axis (another designation is the N axis) is the axis directed to the north. The Z axis (another designation is the Up axis) is an axis directed vertically upward. The orientation of the XYZ trihedron, due to the rotation of the earth and the movement of the vehicle, is constantly shifting with angular velocities.

\omega_E=-V_N/R \omega_N=V_E/R+U cos(\varphi) \omega_(Up)=\frac(V_E)(R)tg(\varphi)+U sin(\varphi) The main disadvantage in practical application GSK in navigation is the large angular velocity of this system at high latitudes, increasing to infinity at the pole. Therefore, instead of the GSK, a semi-free in azimuth CS is used. A half-free in azimuth CS differs from a GSK only in one equation, which has the form:

\omega_(Up)=Usin(\varphi) Accordingly, the system has the same initial position, that the GCS and their orientation also coincide with the only difference that its axes X_w and Y_w are deviated from the corresponding axes of the GCS by an angle \varepsilon for which the equation is valid

d \varepsilon/dt=-\frac(V_E)(R)tg(\varphi) The conversion between the GSK and the semi-free CS in azimuth is carried out according to the formula

N=Y_w cos(\varepsilon)+X_w sin(\varepsilon) E=-Y_w sin(\varepsilon)+X_w cos(\varepsilon) In reality, all calculations are carried out in this system, and then, to produce output information, a transformation occurs coordinates in GSK. To record geographic coordinates, the WGS84 system is used.

Coordinates (latitude from -90° to +90°, longitude from -180° to +180°) can be written:

in ° degrees as a decimal (modern version) in ° degrees and "minutes s decimal in ° degrees, "minutes and " seconds with decimal fraction (historically established form of notation) The decimal separator is always a dot. Positive coordinate signs are represented by a (in most cases omitted) "+" sign, or by the letters: "N" - north latitude and "E" - east longitude. Negative signs coordinates are represented either by the sign “-” or by the letters: “S” - southern latitude and “W” - western longitude. Letters can be placed either in front or behind.

There are no uniform rules for recording coordinates.

Search engine maps by default show coordinates in degrees and decimals, with "-" signs for negative longitude. On Google maps and Yandex maps, first latitude, then longitude (until October 2012, Yandex maps adopted reverse order: first longitude, then latitude). These coordinates are visible, for example, when plotting routes from arbitrary points. Other formats are also recognized when searching.

In navigators, by default, degrees and minutes with a decimal fraction with a letter designation are often shown, for example, in Navitel, in iGO. You can enter coordinates in accordance with other formats. The degrees and minutes format is also recommended for maritime radio communications. [source not specified 1281 days]

At the same time, the original method of recording with degrees, minutes and seconds is often used. Currently, coordinates can be written in one of many ways or duplicated in two main ways (with degrees and with degrees, minutes and seconds). As an example, options for recording the coordinates of the sign “Zero kilometer of roads Russian Federation» -- 55°45′21″ N. w. 37°37′04″ E. d. (G) (O) (I):

55.755831°, 37.617673° -- degrees N55.755831°, E37.617673° -- degrees (+ additional letters) 55°45.35"N, 37°37.06"E -- degrees and minutes (+ additional letters) 55° 45"20.9916"N, 37°37"3.6228"E -- degrees, minutes and seconds (+ additional letters) If necessary, the formats can be recalculated independently: 1° = 60" minutes, 1" minute = 60" seconds. You can also use specialized services.

They are necessary in order to find a specific object on a globe or geographical map. Geographic coordinates include geographic latitude, geographic longitude And absoluteheight .

All geographical features on Earth, in addition to the poles, they have latitude and longitude. All meridians of the Earth at the pole converge at one point. Therefore, the North and South Poles only have a latitude of 90 degrees.

Maps with parallels and meridians marked on them help sailors find their way among the vast expanses of the ocean. From them you can determine where the ship is, how long it will have to sail, and what lands it will meet along the way. Sailors and travelers determine the latitude and longitude of an area using special instruments, working with which requires knowledge of mathematics and astronomy.

Geographic latitude points are the magnitude of the arc in degrees between the equator and this point. The geographic latitude of any place on the globe is expressed in degrees, which are counted from the Equator (0°) to the poles (90°).

To determine the geographic latitude of a place on a map or globe, you need to know what parallel it is on. The value of parallels from 0 degrees at the equator to 90 degrees at the pole is written along the prime, Greenwich meridian or on the side of the map frame. All points on the earth's surface north of the equator have a northern latitude, all points in the southern hemisphere have a southern latitude.

On the map of the hemispheres in the atlas, parallels are drawn through 20°, therefore, not all points on the globe are on the designated parallels.

Determination of latitude

The Suez Canal is located at 30° north latitude (abbreviated: N), for example, a parallel of 60 degrees runs through St. Petersburg. This means that the city lies at 60 degrees north latitude (N).

Moscow, located in the Northern Hemisphere, is located between 40° N. w. and 60° N. w. It is not difficult to guess that the latitude of Moscow is approximately 55.5° N. w. (55 degrees 30 minutes N). Both Moscow, St. Petersburg, and the Suez Canal are located north of the Equator, so their latitude is north; any point south of the Equator will have a southern latitude (abbreviated: S). Thus, Kerguelen Island in the Indian Ocean is located at 50° south. w.

A parallel of 30 degrees runs through the center of the Drake Passage in the Southern Hemisphere. The latitude of Lake Victoria in Africa is 0 degrees.

To accurately determine a point on a globe or on a map, you need to know, in addition to the geographic latitude, the geographic longitude of this point.

Geographical longitude points are the magnitude of the arc in degrees from the prime meridian to this point on the earth's surface.

Like latitude, longitude is expressed in degrees, which are measured from the prime meridian. The prime meridian was chosen arbitrarily, and it passes through the Greenwich Observatory, located near the city of London. The Greenwich meridian on the globe and geographical map is shown as a thicker line, and at its intersection with the equator it is written: 0° (degrees). All other meridians are also labeled in degrees at the equator. These degrees increase in both directions from the zero, Greenwich, meridian and reach a value of 180 degrees on the other side of the Earth. The 180th meridian is also shown with a thick line. The two halves of the Earth's circumference - the Eastern and Western Hemispheres - are separated by 180 degrees.

Determination of longitude

To the east of the Greenwich meridian there will be eastern longitude (abbreviated: E.L.), to the west - western longitude (W.L.). Degrees of longitude on a globe and a map of the hemispheres are indicated at the Equator. Thus, the Suez Canal is located at 32° east. d., and the Strait of Gibraltar - already at 5° W. d. Material from the site

Through city of St. Petersburg passes the 30 degree meridian in the Eastern Hemisphere. This means that the longitude of this city is 30 degrees east (30° east).

Through Bering Strait, which divides Eurasia and North America, passes the 170th meridian of the Western Hemisphere. This means its longitude is 170° west longitude (170° west longitude).

Moscow city is located in the Eastern Hemisphere between the meridians of 30 degrees and 40 degrees. Divide this distance into 10 parts - 10 degrees. The longitude of Moscow will be approximately 37 degrees east longitude. It can be determined more precisely - 37.5° east. Degrees are divided into minutes; there are 60 minutes in one degree. They also say that Moscow is located at 37 degrees 30 minutes east longitude.

On globes and geographical maps there is 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 - the angle between plumb line at any specific 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 at their intersection 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 detect 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 a settlement by name using the search.
Right-click on the desired location. Select the required item from the menu that opens. 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 indicate the geographic latitude and longitude of the center of that 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 that is calculated from the 50th parallel to the desired object. This number is 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 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 geographic longitude coordinates 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 this value you need 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.”

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 is considered 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 altitude, 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.

For example.

Moscow has a longitude of 37°37′ (east), and Khabarovsk -135°05′, that is, lies east of 97°28′. What time do these cities have at the same moment? Simple calculations show that if it is 13 hours in Moscow, then in Khabarovsk it is 19 hours 30 minutes.

The figure below shows the design of the frame of a sheet of any card. As can be seen from the figure, in the corners of this map the longitude of the meridians and the latitude of the parallels that form the frame of the sheet of this map are written.

On all sides the frame has scales divided into minutes. For both latitude and longitude. Moreover, each minute is divided by dots into 6 equal sections, which correspond to 10 seconds of longitude or latitude.

Thus, in order to determine the latitude of any point M on the map, it is necessary to draw a line through this point, parallel to the lower or upper frame of the map, and read the corresponding degrees, minutes, seconds on the right or left along the latitude scale. In our example, point M has a latitude of 45°31’30”.

Similarly, drawing a vertical line through point M parallel to the lateral (closest to the given point) meridian of the border of this map sheet, we read the longitude (eastern) equal to 43°31’18”.

Application to topographic map points at given geographic coordinates.

Drawing a point on a map at specified geographic coordinates is done in the reverse order. First, the indicated geographic coordinates are found on the scales, and then parallel and perpendicular lines are drawn through them. Their intersection will show a point with the given geographic coordinates.

Based on materials from the book “Map and Compass are My Friends.”
Klimenko A.I.

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