Geographical coordinates as determined by the map. Latitude and longitude - what is it in geography

Coordinates called angular and linear quantities (numbers) that determine the position of a point on a surface or in space.

In topography, such coordinate systems are used that allow the most simple and unambiguous determination of the position of points on the earth's surface, both from the results of direct measurements on the ground and using maps. These systems include geographic, flat rectangular, polar and bipolar coordinates.

Geographical coordinates(Fig.1) - angular values: latitude (j) and longitude (L), which determine the position of the object on the earth's surface relative to the origin of coordinates - the point of intersection of the initial (Greenwich) meridian with the equator. On the map, the geographic grid is indicated by a scale on all sides of the map frame. The western and eastern sides of the frame are meridians, while the northern and southern sides are parallels. In the corners of the map sheet, the geographical coordinates of the points of intersection of the sides of the frame are signed.

Rice. 1. System geographical coordinates on the earth's surface

In the geographic coordinate system, the position of any point on the earth's surface relative to the origin of coordinates is determined in angular measure. For the beginning, in our country and in most other states, the point of intersection of the initial (Greenwich) meridian with the equator is accepted. Being, therefore, the same for our entire planet, the system of geographical coordinates is convenient for solving problems of determining the relative position of objects located at considerable distances from each other. Therefore, in military affairs, this system is used mainly for conducting calculations related to the use of long-range combat weapons, such as ballistic missiles, aviation, etc.

Planar rectangular coordinates(Fig. 2) - linear quantities that determine the position of the object on the plane relative to the accepted origin - the intersection of two mutually perpendicular lines (coordinate axes X and Y).

In topography, each 6-degree zone has its own system of rectangular coordinates. The X-axis is the axial meridian of the zone, the Y-axis is the equator, and the point of intersection of the axial meridian with the equator is the origin of coordinates.

Rice. 2. System of flat rectangular coordinates on maps

The system of flat rectangular coordinates is zonal; it is set for each six-degree zone into which the Earth's surface is divided when it is depicted on maps in the Gaussian projection, and is intended to indicate the position of images of points on the earth's surface on a plane (map) in this projection.

The origin of coordinates in the zone is the point of intersection of the axial meridian with the equator, relative to which the position of all other points of the zone is determined in a linear measure. The origin of the zone coordinates and its coordinate axes occupy a strictly defined position on the earth's surface. Therefore, the system of flat rectangular coordinates of each zone is connected both with the coordinate systems of all other zones, and with the system of geographical coordinates.

The use of linear quantities to determine the position of points makes the system of flat rectangular coordinates very convenient for making calculations both when working on the ground and on the map. Therefore, in the troops, this system finds the most wide application. Rectangular coordinates indicate the position of terrain points, their battle formations and targets, with their help they determine the relative position of objects within one coordinate zone or in adjacent sections of two zones.

Polar and bipolar coordinate systems are local systems. In military practice, they are used to determine the position of some points relative to others on a comparatively small areas terrain, for example, when targeting, marking landmarks and targets, drawing up terrain diagrams, etc. These systems can be associated with systems of rectangular and geographical coordinates.

2. Determination of geographical coordinates and mapping of objects by known coordinates

The geographical coordinates of a point located on the map are determined from the parallels and meridians closest to it, the latitude and longitude of which are known.

The frame of the topographic map is divided into minutes, which are separated by dots into divisions of 10 seconds each. Latitudes are indicated on the sides of the frame, and longitudes are indicated on the northern and southern sides.

Rice. 3. Determination of the geographical coordinates of a point on the map (point A) and drawing a point on the map by geographical coordinates (point B)

Using the minute frame of the map, you can:

1 . Determine the geographic coordinates of any point on the map.

For example, the coordinates of point A (Fig. 3). To do this, use a measuring compass to measure the shortest distance from point A to the southern frame of the map, then attach the meter to the western frame and determine the number of minutes and seconds in the measured segment, add the resulting (measured) value of minutes and seconds (0 "27") with the latitude of the southwestern corner of the frame - 54 ° 30 ".

Latitude points on the map will be equal to: 54°30"+0"27" = 54°30"27".

Longitude defined in a similar way.

Using a measuring compass, measure the shortest distance from point A to the western frame of the map, apply the measuring compass to the southern frame, determine the number of minutes and seconds in the measured segment (2 "35"), add the obtained (measured) value to the longitude of the southwestern corner frames - 45°00".

Longitude points on the map will be equal to: 45°00"+2"35" = 45°02"35"

2. Put any point on the map according to the given geographical coordinates.

For example, point B latitude: 54°31 "08", longitude 45°01 "41".

To map a point in longitude, it is necessary to draw a true meridian through a given point, for which connect the same number of minutes along the northern and southern frames; to plot a point in latitude on a map, it is necessary to draw a parallel through this point, for which connect the same number of minutes along the western and eastern frames. The intersection of two lines will determine the location of point B.

3. Rectangular coordinate grid on topographic maps and its digitization. Additional grid at the junction of coordinate zones

The coordinate grid on the map is a grid of squares formed by lines parallel to the coordinate axes of the zone. The grid lines are drawn through an integer number of kilometers. Therefore, the coordinate grid is also called the kilometer grid, and its lines are kilometer.

On the 1:25000 map, the lines forming the coordinate grid are drawn through 4 cm, that is, through 1 km on the ground, and on maps 1:50000-1:200000 through 2 cm (1.2 and 4 km on the ground, respectively). On the 1:500000 map, only the exits of the coordinate grid lines are plotted on the inner frame of each sheet after 2 cm (10 km on the ground). If necessary, coordinate lines can be drawn on the map along these exits.

On the topographic maps the values ​​of the abscissas and ordinates of the coordinate lines (Fig. 2) are signed at the exits of the lines behind the inner frame of the sheet and nine places on each sheet of the map. Full values abscissas and ordinates in kilometers are signed near the coordinate lines closest to the corners of the map frame and near the intersection of the coordinate lines closest to the northwestern corner. The rest of the coordinate lines are signed in abbreviated form with two digits (tens and units of kilometers). Signatures near the horizontal lines of the coordinate grid correspond to distances from the y-axis in kilometers.

Signatures near the vertical lines indicate the zone number (one or two first digits) and the distance in kilometers (always three digits) from the origin of coordinates, conditionally moved to the west of the zone's central meridian by 500 km. For example, the signature 6740 means: 6 - zone number, 740 - distance from the conditional origin in kilometers.

The outputs of the coordinate lines are given on the outer frame ( additional grid) coordinate systems of the adjacent zone.

4. Determination of rectangular coordinates of points. Drawing points on the map by their coordinates

By coordinate grid With the help of a compass (ruler) you can:

1. Determine the rectangular coordinates of a point on the map.

For example, points B (Fig. 2).

For this you need:

• write X - digitization of the lower kilometer line of the square in which point B is located, i.e. 6657 km;
• measure along the perpendicular the distance from the lower kilometer line of the square to point B and, using the linear scale of the map, determine the value of this segment in meters;
• add the measured value of 575 m with the digitization value of the lower kilometer line of the square: X=6657000+575=6657575 m.

The Y ordinate is determined in the same way:

• write the Y value - the digitization of the left vertical line of the square, i.e. 7363;
• measure the perpendicular distance from this line to point B, i.e. 335 m;
• add the measured distance to the Y digitization value of the left vertical line of the square: Y=7363000+335=7363335 m.

2. Put the target on the map according to the given coordinates.

For example, point G by coordinates: X=6658725 Y=7362360.

For this you need:

• find the square in which the point G is located by the value of whole kilometers, i.e. 5862;
• set aside from the lower left corner of the square a segment on the scale of the map, equal to the difference between the abscissa of the target and the lower side of the square - 725 m;
• from the obtained point along the perpendicular to the right, set aside a segment equal to the difference in the ordinates of the target and the left side of the square, i.e. 360 m.

Rice. 2. Determining the rectangular coordinates of a point on the map (point B) and plotting a point on the map using rectangular coordinates (point D)

5. Accuracy of determining coordinates on maps of various scales

The accuracy of determining geographical coordinates on maps 1:25000-1:200000 is about 2 and 10 "" respectively.

The accuracy of determining the rectangular coordinates of points on a map is limited not only by its scale, but also by the magnitude of the errors allowed when shooting or compiling a map and drawing various points and terrain objects on it

Geodetic points and are plotted most accurately (with an error not exceeding 0.2 mm) on the map. objects that stand out most sharply on the ground and are visible from afar, having the value of landmarks (individual bell towers, factory chimneys, tower-type buildings). Therefore, the coordinates of such points can be determined with approximately the same accuracy with which they are plotted on the map, i.e. for a map of a scale of 1:25000 - with an accuracy of 5-7 m, for a map of a scale of 1:50000 - with an accuracy of -10- 15 m, for a map at a scale of 1:100000 - with an accuracy of 20-30 m.

The remaining landmarks and contour points are plotted on the map, and, therefore, are determined from it with an error of up to 0.5 mm, and points related to contours that are not clearly expressed on the ground (for example, the contour of a swamp), with an error of up to 1 mm.

6. Determining the position of objects (points) in systems of polar and bipolar coordinates, mapping objects in direction and distance, in two angles or in two distances

System flat polar coordinates(Fig. 3, a) consists of a point O - the origin, or poles, and the initial direction of the OR, called polar axis.

Rice. 3. a – polar coordinates; b – bipolar coordinates

The position of the point M on the ground or on the map in this system is determined by two coordinates: the position angle θ, which is measured clockwise from the polar axis to the direction to the determined point M (from 0 to 360 °), and the distance OM = D.

Depending on the task being solved, an observation point, a firing position, a starting point for movement, etc. are taken as a pole, and a geographic (true) meridian, a magnetic meridian (the direction of a magnetic compass needle) or a direction to some landmark is taken as a polar axis .

These coordinates can be either two position angles that determine directions from points A and B to the desired point M, or distances D1=AM and D2=BM to it. The position angles, as shown in Fig. 1, b, are measured at points A and B or from the direction of the basis (i.e., angle A=BAM and angle B=ABM) or from any other directions passing through points A and B and taken as initial ones. For example, in the second case, the location of the point M is determined by the position angles θ1 and θ2, measured from the direction of the magnetic meridians. System flat bipolar (two-pole) coordinates(Fig. 3, b) consists of two poles A and B and a common axis AB, called the basis or base of the serif. The position of any point M relative to the two data on the map (terrain) points A and B is determined by the coordinates that are measured on the map or on the terrain.

Drawing the detected object on the map

This is one of highlights in object detection. The accuracy of determining its coordinates depends on how accurately the object (target) will be mapped.

Having found an object (target), you must first accurately determine by various features, which is found. Then, without stopping the observation of the object and without revealing yourself, put the object on the map. There are several ways to plot an object on a map.

visually: Places a feature on the map when it is close to a known landmark.

By direction and distance: to do this, you need to orient the map, find the point of your standing on it, sight on the map the direction to the detected object and draw a line to the object from the point of your standing, then determine the distance to the object by measuring this distance on the map and commensurate it with the scale of the map.

Rice. 4. Drawing a target on the map with a straight cut from two points.

If in this way it is graphically impossible to solve the problem (the enemy interferes, poor visibility, etc.), then you need to accurately measure the azimuth to the object, then translate it into a directional angle and draw a direction on the map from the standing point, on which to plot the distance to the object.

To get the directional angle, you need to add the magnetic declination of this map (direction correction) to the magnetic azimuth.

straight serif. In this way, an object is put on a map of 2-3 points from which it is possible to observe it. To do this, from each selected point, the direction to the object is drawn on the oriented map, then the intersection of straight lines determines the location of the object.

7. Ways of targeting on the map: in graphic coordinates, flat rectangular coordinates (full and abbreviated), by squares of a kilometer grid (up to a whole square, up to 1/4, up to 1/9 of a square), from a landmark, from a conditional line, by azimuth and target range, in the bipolar coordinate system

The ability to quickly and correctly indicate targets, landmarks and other objects on the ground is important for controlling subunits and fire in combat or for organizing combat.

Target designation in geographic coordinates It is used very rarely and only in those cases when the targets are removed from a given point on the map at a considerable distance, expressed in tens or hundreds of kilometers. In this case, geographical coordinates are determined from the map, as described in question No. 2 of this lesson.

The location of the target (object) is indicated by latitude and longitude, for example, height 245.2 (40 ° 8 "40" N, 65 ° 31 "00" E). On the eastern (western), northern (southern) sides of the topographic frame, mark the position of the target in latitude and longitude with a prick of a compass. From these marks, perpendiculars are lowered into the depth of the sheet of the topographic map until they intersect (commander lines are applied, standard sheets paper). The point of intersection of the perpendiculars is the position of the target on the map.

For approximate target designation rectangular coordinates it is enough to indicate on the map the square of the grid in which the object is located. The square is always indicated by the numbers of kilometer lines, the intersection of which forms the southwestern (lower left) corner. When indicating the square, the cards follow the rule: first they name two numbers signed at the horizontal line (at the western side), that is, the “X” coordinate, and then two numbers at the vertical line (south side of the sheet), that is, the “Y” coordinate. In this case, "X" and "Y" are not spoken. For example, enemy tanks are spotted. When transmitting a report by radiotelephone, the square number is pronounced: eighty-eight zero two.

If the position of a point (object) needs to be determined more accurately, then full or abbreviated coordinates are used.

Work with full coordinates. For example, it is required to determine the coordinates of a road sign in square 8803 on a map at a scale of 1:50000. First, determine what is the distance from the lower horizontal side of the square to the road sign (for example, 600 m on the ground). In the same way, measure the distance from the left vertical side of the square (for example, 500 m). Now, by digitizing kilometer lines, we determine the full coordinates of the object. The horizontal line has the signature 5988 (X), adding the distance from this line to the road sign, we get: X=5988600. In the same way, we determine the vertical line and get 2403500. The full coordinates of the road sign are as follows: X=5988600 m, Y=2403500 m.

Abbreviated coordinates respectively will be equal: X=88600 m, Y=03500 m.

If it is required to clarify the position of the target in a square, then target designation is used by letter or number inside the square of the kilometer grid.

When targeting in a literal way inside the square of the kilometer grid, the square is conditionally divided into 4 parts, each part is assigned a capital letter of the Russian alphabet.

The second way - digital way target designation inside the kilometer grid square (target designation by snail ). This method got its name from the arrangement of conditional digital squares inside the square of the kilometer grid. They are arranged as if in a spiral, while the square is divided into 9 parts.

When targeting in these cases, they name the square in which the target is located, and add a letter or number that specifies the position of the target inside the square. For example, a height of 51.8 (5863-A) or a high-voltage support (5762-2) (see Fig. 2).

Target designation from a landmark is the simplest and most common method of target designation. With this method of target designation, the nearest landmark to the target is first called, then the angle between the direction to the landmark and the direction to the target in goniometer divisions (measured with binoculars) and the distance to the target in meters. For example: "Landmark two, forty to the right, further two hundred, at a separate bush - a machine gun."

target designation from the conditional line usually used in combat vehicles. With this method, two points are selected on the map in the direction of action and connected by a straight line, relative to which target designation will be carried out. This line is indicated by letters, divided into centimeter divisions and numbered starting from zero. Such a construction is done on the maps of both the transmitting and receiving target designation.

Target designation from a conditional line is usually used in combat vehicles. With this method, two points are selected on the map in the direction of action and connected by a straight line (Fig. 5), relative to which target designation will be carried out. This line is indicated by letters, divided into centimeter divisions and numbered starting from zero.

Rice. 5. Target designation from a conditional line

Such a construction is done on the maps of both the transmitting and receiving target designation.

The position of the target relative to the conditional line is determined by two coordinates: a segment from the starting point to the base of the perpendicular, lowered from the target location point to the conditional line, and a segment of the perpendicular from the conditional line to the target.

When targeting, the conditional name of the line is called, then the number of centimeters and millimeters contained in the first segment, and, finally, the direction (left or right) and the length of the second segment. For example: “Direct AC, five, seven; zero to the right, six - NP.

Target designation from a conditional line can be issued by indicating the direction to the target at an angle from the conditional line and the distance to the target, for example: "Direct AC, right 3-40, one thousand two hundred - machine gun."

target designation in azimuth and range to the target. The azimuth of the direction to the target is determined using a compass in degrees, and the distance to it is determined using an observation device or by eye in meters. For example: "Azimuth thirty-five, range six hundred - a tank in a trench." This method is most often used in areas where there are few landmarks.

8. Problem solving

Determining the coordinates of terrain points (objects) and target designation on the map is practiced practically on training maps using pre-prepared points (marked objects).

Each student determines geographic and rectangular coordinates (maps objects at known coordinates).

Methods of target designation on the map are worked out: in flat rectangular coordinates (full and abbreviated), in squares of a kilometer grid (up to a whole square, up to 1/4, up to 1/9 of a square), from a landmark, in azimuth and range of the target.

Geographical coordinates -angular values: latitude (p and longitude TO, determining the position of objects on the earth's surface and on the map (Fig. 20).

Latitude is the angle (p between the plumb line at a given point and the plane of the equator. Latitudes vary from 0 to 90 °; in the northern hemisphere they are called northern, in the southern - southern.

Longitude - dihedral angle To between the plane of the prime meridian and the plane of the meridian of a given point on the earth's surface. The meridian passing through the center of the Greenwich Observatory (London area) is taken as the initial meridian. The prime meridian is called the Greenwich meridian. Longitudes vary from 0 to 180°. Longitudes counted east of the Greenwich meridian are called eastern longitudes, and longitudes,. counted to the west - western.

Geographic coordinates obtained from astronomical observations are called astronomical, and coordinates obtained by geodetic methods and determined from topographic maps are called geodetic. The values ​​of astronomical and geodetic coordinates of the same points differ slightly - in linear measures, on average, by 60-90 m.

Geographic (cartographic) grid formed on the map by lines of parallels and meridians. It is used for targeting and determining the geographical coordinates of objects.

On topographic maps, the lines of parallels and meridians serve as the internal frames of the sheets; their latitudes and longitudes are signed at the corners of each sheet. On sheets of maps for the Western Hemisphere, the inscription "West of Greenwich" is placed in the northwestern corner of the frame.

Rice. twenty.Geographical coordinates: f-latitude of point L; TO- point longitude BUT

On sheets of maps at a scale of 1:50000, 1:100000 and 1:200000, the intersections of the mean parallels and meridians are shown and their digitization is given in degrees and minutes. According to these data, the signatures of latitudes and longitudes of the sides of the frames of sheets cut off when gluing the map are restored. In addition, along the sides of the frames inside the sheet, small (2-3 mm) strokes in one minute, along which parallels and meridians can be drawn on a map glued from many sheets.

On maps of scale 1:25,000, 1:50,000 and 1:200,000, the sides of the frames are divided into segments equal to one minute in degrees. Minute segments are shaded through one and divided by dots (except for the map at a scale of 1:200000) into parts of 10".

On the sheets of the map at a scale of 1:500,000, the parallels are drawn through 30", and the meridians through 20"; on maps of scale 1:1000000

parallels are drawn through 1 °, meridians - through 40 ". Inside each sheet of the map, on the lines of parallels and meridians, their latitudes and longitudes are signed, which allow determining geographical coordinates on a large gluing of maps.

Definition geographic coordinates of the object on the map is made along the parallels and meridians closest to it, the latitude and longitude of which are known. On maps of scale 1:25000-

1:200,000, for this, as a rule, it is necessary to first draw a parallel to the south of the object and a meridian to the west, connecting the corresponding strokes along the frame of the map sheet with lines. The latitude of the parallel and the longitude of the meridian are calculated and signed on the map (in degrees and minutes). Then the segments from the object to the parallel and the meridian are evaluated in angular measure (in seconds or fractions of a minute). ( Ami and Amiin fig. 21), comparing their linear dimensions with the minute (second) intervals on the sides of the frame. The value of the segment At\ parallels are added to the latitude, and the segmentami-to the longitude of the meridian and get the desired geographical coordinates of the object - latitude and longitude.

On fig. 21 shows an example of determining the geographical coordinates of an object BUT, its coordinates are: north latitude 54°35"40", east longitude 37°41"30".

Drawing an object on the map by geographical coordinates. On the western and eastern sides of the frame of the map sheet, the readings corresponding to the latitude of the object are marked with dashes. The latitude reading starts from the digitization of the southern side of the frame and continues in minute and second intervals. Then a parallel line of the object is drawn through these dashes.

The meridian of the object is built in the same way, only its longitude is measured along the southern and northern sides of the frame. The intersection point of the parallel and the meridian will indicate the position of the object on the map.

On fig. 21 is an example of mapping an object AT at coordinates: 54°38",3 and 37°34",7.

The ability to determine where the latitude or longitude is on the map is important for a person. Especially when there was an accident and you need to quickly make a decision and transfer the coordinates to the police. She will be recognized different methods. They mean the angle that is a vertical line and 0 parallel at a predetermined point. The value is only up to 90 degrees.

Do not forget that the equator divides the earth into northern and southern hemispheres. Therefore, the latitude of earthly points that are higher than the longest parallel are northern, and if they are located below, then southern.

How to find out the latitude of any object?

You can determine the latitude and longitude on the map. Look at which parallel the object is marked. If it is not specified, then independently calculate the distance between neighboring lines. Then find the degree of parallel you are looking for.

At the equator, geographic latitude is 0°. Points that are on the same parallel will have the same latitude. If you take a map, you will see it on the frames, if a globe, then where the parallels intersect with 0° and 180° meridians. Geographic latitudes range from 0° and only up to 90° (near the poles).

5 major latitudes

Take a map, there you will see the main parallels. Thanks to them, the coordinates are easier to recognize. From the latitudinal line to the line, territories are located. They belong to one of the areas: temperate or equatorial, arctic or tropics.

The equator is the longest parallel. Lines that are lower or higher decrease towards the poles. The latitude of the equator is 0°. This is the point from which the parallels are counted towards the south or north. The area that starts from the equator and stretches to the tropics is the equatorial region. Tropic north - the main parallel. It is always marked on the maps of the world.

You can find the exact coordinates of 23° 26 min. and 16 sec. north of the equator. This parallel is also called the Tropic of Cancer. Tropic South is a parallel located at 23° 26 min. and 16 sec. south of the equator. It is called the Tropic of Capricorn. The area that is located in the middle of the line and to the equator are tropical regions.

At 66° 33 min. and 44 sec. Just above the equator is the Arctic Circle. This is the border, beyond it the duration of the night increases. Near the Pole it is 40 calendar days.

Latitude of the Antarctic Circle -66° 33 min. and 44 sec. And this is the border, and beyond it there are polar days and nights. The regions between the tropics and the described lines are temperate, and those beyond them are called polar.

Instruction

Step #1

Everyone knows that the equator divided the earth into southern and northern hemispheres. In addition to the equator, there are parallels. These are circles that are parallel to the equator itself. Meridians are conditional lines that are perpendicular to the equator.

The zero meridian passes through the observatory, it is called the Greenwich observatory and it is located in London. That's why they say so: "Greenwich Meridian". The system, which includes parallels with meridians, creates a grid of coordinates. It is used when they want to determine where an object is located.

Step #2

Does the geographic latitude show this point to the south or north of the equator? It defines the angle 0° and to 90°. The angle begins to count from the equator and to the south or north pole. So you can determine the coordinates, they say that the latitude is southern or northern.

Step #3

Geographic coordinates are measured in minutes with seconds, and most importantly - in degrees. A degree of a certain latitude is 1/180 of any of the meridians. The average length of 1 degree is 111.12 km. A minute in length is 1852 m. The diameter of Mother Earth is 12713 km. This is the distance from pole to pole.

Step #4

To find out latitude 1 in the described way, you need a plumb line with a protractor. You can make a protractor yourself. Take a few rectangular planks. Fasten them like compasses so that they change the angle between them.

Step #5

Take the thread. Hang a load (plumb) on it. Anchor the thread in the center of your protractor. Point the base of the protractor at the polar star. Do some geometric calculations. Specifically, from the angle that is between the plumb line and the base of your protractor, immediately subtract 90 °. This result is the angle that passes between the polar star and the horizon. This angle is the geographic latitude where you are.

Another way

There is another option, how you can find the coordinates. It doesn't look like the first one. Wake up before sunrise and spot its beginning, and then the sunset. Pick up a monogram to find the latitude. On the left of the monogram, set aside how long the daylight hours lasted, and write the date on the right.

Even in the middle of the XVIII century. such coordinates could be learned on the basis of astronomical observations. In the 20s. The 20th century can already be contacted by radio and determine the coordinates with special tools.

Every place on earth can be identified by a global coordinate system of latitude and longitude. Knowing these parameters, it is easy to find any location on the planet. The coordinate system has been helping people in this for several centuries in a row.

Historical prerequisites for the emergence of geographical coordinates

When people began to travel long distances across deserts and seas, they needed a way to fix their position and know in which direction to move so as not to get lost. Before latitude and longitude were on a map, the Phoenicians (600 BC) and Polynesians (400 AD) used the starry sky to calculate latitude.

Quite complex devices have been developed over the centuries, such as the quadrant, the astrolabe, the gnomon, and the Arabic kamal. All of them were used to measure the height of the sun and stars above the horizon and thereby measure latitude. And if the gnomon is just a vertical stick that casts a shadow from the sun, then the kamal is a very peculiar device.

It consisted of a rectangular wooden plank measuring 5.1 by 2.5 cm, to which a rope with several equally spaced knots was attached through a hole in the middle.

These instruments determined the latitude even after the invention until that time, until they invented reliable method determining latitude and longitude on the map.

Navigators for hundreds of years did not have an accurate idea of ​​the location due to the lack of a concept of the value of longitude. There was no precise time device in the world, such as a chronometer, so calculating longitude was simply impossible. Not surprisingly, early navigation was problematic and often resulted in shipwrecks.

Without a doubt, the pioneer of revolutionary navigation was Captain James Cook, who traveled through the expanses Pacific Ocean thanks to technical genius Henry Thomas Harrison. Harrison developed the first navigational clock in 1759. Keeping accurate Greenwich Mean Time, Harrison's clock allowed sailors to determine how many hours were at a point and at a location, after which it became possible to determine longitude from east to west.

Geographic coordinate system

The geographic coordinate system defines two-dimensional coordinates based on the surface of the Earth. It has an angular unit, a prime meridian and an equator with zero latitude. Earth conventionally divided into 180 degrees of latitude and 360 degrees of longitude. Lines of latitude are placed parallel to the equator, they are horizontal on the map. Lines of longitude connect the North and South Poles and are vertical on the map. As a result of the overlay, geographic coordinates are formed on the map - latitude and longitude, with which you can determine the position on the surface of the Earth.

This geographic grid gives a unique latitude and longitude for every position on Earth. To increase the accuracy of measurements, they are further subdivided into 60 minutes, and each minute into 60 seconds.

The equator is located at right angles to the Earth's axis, approximately halfway between the North and South Poles. At an angle of 0 degrees, it is used in the geographic coordinate system as the starting point for calculating latitude and longitude on the map.

Latitude is defined as the angle between the equatorial line of the Earth's center and the location of its center. The North and South Poles have a width angle of 90. To distinguish places in the Northern Hemisphere from the Southern Hemisphere, the width is additionally provided in the traditional spelling with N for north or S for south.

The earth is tilted about 23.4 degrees, so to find the latitude at the summer solstice, you need to add 23.4 degrees to the angle you are measuring.

How to determine the latitude and longitude on the map during the winter solstice? To do this, subtract 23.4 degrees from the angle that is being measured. And in any other period of time, you need to determine the angle, knowing that it changes by 23.4 degrees every six months and, therefore, about 0.13 degrees per day.

In the northern hemisphere, one can calculate the tilt of the Earth, and therefore latitude, by looking at the angle of the North Star. At the North Pole it will be 90 from the horizon, and at the equator it will be directly ahead of the observer, 0 degrees from the horizon.

Important latitudes:

• North and South polar circles, each is at 66 degrees 34 minutes north and south latitude respectively. These latitudes limit the areas around the poles where the sun does not set at the summer solstice, so the midnight sun dominates there. On the winter solstice, the sun does not rise here, the polar night sets in.
• Tropics are located at 23 degrees 26 minutes in the northern and southern latitudes. These latitudinal circles mark the solar zenith with the summer solstice of the northern and southern hemispheres.
• Equator lies at latitude 0 degrees. The equatorial plane runs approximately in the middle of the Earth's axis between the north and south poles. The equator is the only circle of latitude that corresponds to the circumference of the earth.

Latitude and longitude on the map are important geographic coordinates. Longitude is much more difficult to calculate than latitude. The earth rotates 360 degrees a day, or 15 degrees an hour, so there is a direct relationship between longitude and the times the sun rises and sets. The Greenwich meridian is indicated by 0 degrees of longitude. The sun sets an hour earlier every 15 degrees east of it and an hour later every 15 degrees west. If you know the difference between the sunset time of a location and another famous place, then you can understand how far east or west is from it.

The lines of longitude run from north to south. They converge at the poles. And the longitude coordinates are between -180 and +180 degrees. The Greenwich meridian is the zero line of longitude, which measures the east-west direction in a system of geographic coordinates (such as latitude and longitude on a map). In fact, the zero line passes through the Royal Observatory in Greenwich (England). The Greenwich meridian, as the prime meridian, is the starting point for calculating longitude. Longitude is specified as the angle between the center of the prime meridian of the center of the Earth and the center of the center of the Earth. The Greenwich meridian has an angle of 0, and the opposite longitude along which the date line runs has an angle of 180 degrees.

How to find latitude and longitude on a map?

Definition of exact geographical location map depends on its scale. To do this, it is enough to have a map with a scale of 1/100000, or better - 1/25000.

First, the longitude D is determined by the formula:

D \u003d G1 + (G2 - G1) * L2 / L1,

where G1, G2 - the value of the right and left nearest meridians in degrees;

L1 - distance between these two meridians;

Calculation of longitude, for example, for Moscow:

G1 = 36°,

G2 = 42°,

L1 = 252.5 mm,

L2 = 57.0 mm.

Search longitude = 36 + (6) * 57.0 / 252.0 = 37° 36".

We determine the latitude L, it is determined by the formula:

L \u003d G1 + (G2 - G1) * L2 / L1,

where G1, G2 - the value of the lower and upper nearest latitude in degrees;

L1 - distance between these two latitudes, mm;

L2 - distance from the definition point to the left nearest one.

For example, for Moscow:

L1 = 371.0 mm,

L2 = 320.5 mm.

Desired width L = 52" + (4) * 273.5 / 371.0 = 55 ° 45.

We check the correctness of the calculation, for this it is necessary to find the coordinates of latitude and longitude on the map using online services on the Internet.

We establish that the geographical coordinates for the city of Moscow correspond to the calculations:

1. 55° 45" 07" (55° 45" 13) north latitude;
2. 37° 36" 59" (37° 36" 93) East.

Determining location coordinates using iPhone

Accelerating the pace of scientific and technological progress by present stage led to revolutionary discoveries of mobile technology, with the help of which fast and more precise definition geographical coordinates.

For this, there are various mobile applications. On iPhones, this is very easy to do using the Compass app.

Definition order:

1. To do this, click "Settings", and then - "Privacy".
2. Now click "Location Services" at the very top.
3. Scroll down until you see the compass and tap it.
4. If you see that it says "When used on the right side", you can start the definition.
5. If not, tap it and select "When using the app".
6. Open the Compass app and you will see your current location and current GPS coordinates at the bottom of the screen.

Determination of coordinates in an Android phone

Unfortunately, Android doesn't have an official built-in way to get GPS coordinates. However, it is possible to get the coordinates Google Maps, which requires some additional steps:

1. Open Google Maps on Android device and find the desired definition point.
2. Press and hold it anywhere on the screen and drag it to Google Maps.
3. An informational or detailed map.
4. Find the Share option on the information card in the upper right corner. This will bring up a menu with the Share option.

This setup can be done in Google Maps on iOS.

it great way get coordinates, which does not require you to install any additional applications.

You can determine the geographical coordinates of a given point, that is, its latitude and longitude, using a map. On any geographical map there is a degree network, with its help, geographical coordinates are determined.
It is customary to determine and record coordinates in the following order: first latitude, then longitude.
To find the geographic latitude on the map, we need parallels. Let's find the most important parallel - the equator. If it is not signed on the world map, then it corresponds to the value 0°. Note that all parallels on the map have numeric values ​​that can range from 0 to 90 degrees. Note that 90° is the maximum value of geographic latitude, and it corresponds to the poles of the planet. But the Earth has two poles: North and South, they need to be distinguished. The equator we found divides the earth into two hemispheres, all points south of the equator have a southern latitude, all points north of it have a northern latitude. It turns out that the latitude of the North Pole is 90 ° north latitude, and the South Pole is 90 ° south. In geography, a short notation is accepted: instead of the words "northern latitude" it is customary to write N latitude, and instead of "southern latitude": S. latitude. It remains to figure out what to do with the equator, because its latitude is 0 °. As in mathematics, zero is neither positive nor negative number, and in geography, if a point is located on the equator, then its latitude is 0 ° latitude or 0 ° latitude. (neither north nor south).

But what if the point does not lie directly on the parallels and is somewhere between them on the map?
A parallel can be drawn through any point on the map, because there are an infinite number of them. Just for convenience, only a few are depicted on the map, otherwise the entire map will be shaded with them. And the rest of the parallels have to be completed mentally.
Let's try to find the latitude of the source of the Missouri River. This point is in North America, which is located north of the equator, that is, the latitude of our point is northern.
On the map we see that the source is located between the 40th and 60th parallel. This means that its latitude is greater than 40 but less than 60 degrees. Be especially careful in this place, notice that in the Southern Hemisphere the calculation of parallels on the world map goes to opposite side from the North! Always carefully determine more and less than what the latitude of your point should be - between which parallels it lies. Further, since it is customary to determine latitude to a degree, you need to mentally divide the distance between our parallels (40 and 60) by the number of degrees between them (in our case, there are 19 parallels between them - from 41 to 59) and measure which of them approximately lies our point. Here you need to simplify your work: we see that the source of the Missouri is much closer to the 40th parallel. Mentally draw a parallel of 50 °. It is more convenient to do this along the neighboring meridians of the degree network. Now it is clearly seen that the point lies almost in the middle between the 40th and 50th parallels. This means that its latitude is 45 ° north latitude. We also note that absolutely accurate measurements in tasks for finding coordinates are usually not required. According to school atlases, measurement errors are allowed within the division of the degree network; on the world map, this is usually 2 °.

Now that we have learned how to find latitude, you can find geographic longitude in a similar way. It's not much more difficult. Additional complexity arises due to the fact that one equator divides the earth into the Northern and Southern hemispheres, and two meridians into the Western and Eastern hemispheres: zero and one hundred and eightieth. On the world map, we will have to find both of them. All points east of the zero but west of the 180 meridian have east longitude, and all points west of the zero but east of 180 have the west. The zero meridian is also commonly called the initial or Greenwich meridian (Greenwich Observatory in London). It is also customary to shorten the record of longitude. East longitude is written as east longitude, and west longitude is written as west longitude.
What if the point lies on the 0 or 180 meridian? Most likely you have already guessed that their longitude will be simply 0 ° long. or 180°d. - neither western nor eastern.
And the last nuance is the longitude of the planet's poles. We have established that their latitude is 90°, but all the meridians converge at the poles. That is why the longitude of the pole cannot be determined; the North and South Poles have no longitude.

Of course, most of the points on the map for which we are looking for coordinates also lie between the meridians. This means that we will have to do the same as when we were looking for latitude - mentally draw the missing meridians. Let's try this again for the headwaters of the Missouri. We see that it is located in the middle between 100 and 120 meridian west longitude. They lie west of the 0 meridian and east of 180. This means that the longitude of our point is western. The longitude of the point is greater than 100° but less than 120°. It is located almost in the middle, which means that its longitude is approximately equal to 110 ° W. (Actually, 111°, but we repeat that it is ideally difficult to measure coordinates on such a small-scale map - focus on an error of no more than 2° for a world map).

So, we got the approximate coordinates of the source of the Missouri: 45 ° north latitude. and 110°W

As a result - the plan "How to find latitude and longitude"
1) Determine the point located north or south of the equator:
- If to the north - the latitude is northern;
- If to the south - the latitude is south;
- If at the equator - latitude 0°
2) Determine between which parallels a point is shown on the map.
This means to find out - more than what and less than what value will be its latitude.
3) Mentally draw the missing parallels and determine the latitude to a degree.
4) Determine to the west or east of the 0 meridian there is a point.
- If west of 0, but east of 180 - west longitude;
- If east of 0, but west of 180 - east longitude;
- If on the 0th meridian - 0°d., if on the 180th meridian - 180°d;
- If the latitude is 90°, then there is no longitude.
5) Determine between which meridians a point on the map is located.
Find out in what range we are looking for the value of longitude;
6) Mentally draw the missing meridians and determine the longitude to a degree.