When getting into an emergency, a person must first of all be able to navigate the terrain. Sometimes it is necessary to determine the geographic coordinates of your location, for example, to transmit rescue service or for other purposes. There are several handy ways to do this. But first, some theory:

The equator divides the globe into northern and southern hemispheres. There are also parallels and meridians. Parallels are circles parallel to the equator. Meridians are circles perpendicular to the equator. The prime meridian passes through the Greenwich Observatory in London. The system of parallels and meridians is coordinate grid, which is used for positioning and target designation.

Geographical coordinates consist of latitude and longitude, which are angular quantities that can be used to determine the position of a point in any part of the globe.

Geographic longitude - the angle measured from the prime meridian, from 0° to 180°. If the account is kept west of Greenwich, then this will be the western longitude, if east, then the eastern. Longitude indicates how far a point is to the west or east of the prime meridian.

Geographic latitude, shows how much the point is north or south of the equator, and makes an angle from 0 ° to 90 °, counted from the plane of the equator to one of the poles - north or south. It follows that the latitude is also north and south.

Schematic definition of latitude and longitude
Geographic coordinates are measured in degrees, minutes and seconds. A degree of geographic latitude is 1/180 of a meridian. The average length of one degree of latitude corresponds to approximately 111.12 km. The average length of one minute corresponds to 1852 m (10 cables, or 1 nautical mile). The diameter of the Earth (the length of the earth's axis) between the poles is 12713 km.

Determination of geographic longitude
A degree of longitude is 1/360 of the equator. Because the Earth makes a complete revolution on its axis in 24 hours, then in 1 hour of time the Earth passes 15 ° longitude. Respectively:

1° longitude = 4 min. time
1´ = 4 sec time
1" = 1/15 sec time

Based on the above, there is a way to determine the geographic longitude of your location using a watch. To do this, you must have a clock whose time is set at a place with a known longitude and note their readings at local noon, and convert the difference of this time into a degree measure:

Definition of local noon
one). Recalculate your watch to GMT, taking into account the zone corrections (the place in which they are set, if not GMT), daylight savings time and daylight savings.

2). Find noon in the area. To do this, you need to use the gnomon - the oldest sundial, i.e. stuck strictly vertically into the ground with a stick 1-1.5 m. And mark the length of the falling line by marking on the ground. As the sun approaches the zenith, the shadow will begin to shorten, and at the moment when it becomes the shortest, this will be the true solar time at noon in this area, i.e. your sundial show 12 noon. I would like to note that at noon the shadow of the stick will be directed strictly from south to north.
3). Record your watch - this will be Greenwich Mean Time. Further, the correction from the table should be subtracted from this time, taking into account the sign, since the angular velocity of movement is not constant and depends on the time of year, thereby bringing the mean Greenwich time to true solar.
And now calculate the difference between the true solar time at noon, i.e. 12h and the resulting GMT time, taking into account the correction. The result obtained is converted into a degree measure, this will be the geographic longitude of the area.

Example: the date is May 2, your watch is set to Moscow time. Moscow summer time differs from the world summer by 4 hours. At local noon, the clock showed 18 hours 36 minutes. Hence the Greenwich Mean Time at that moment was 14 hours 36 minutes. We make an amendment + 3 min on May 2. Subtract 12 hours from this, we get 2 hours 36 minutes. taking into account the amendment for May 2, we add 3 minutes and translate into an angular measure. And we get 39 ° west longitude, because local noon came later than GMT.
14:36 ​​+ 3min = 14:39 - true solar time
14:39 - 12h = 2:39 = 39° west longitude

Table 1 - Add the correction (with its own sign) to the clock readings to obtain true solar time

The second way is to bring the true solar time at noon to the average, adding to it the correction from table 2, i.e. add the correction to 12h, taking into account the sign


Table 2 - Bringing the true solar time to the average

Example: The date is October 7th. You have determined solar noon, i.e. 12h. Your clock is set to GMT and shows 8:20. True solar time must be converted to the mean, since the GMT clock also shows the mean. This means that the correction for October 7 is -12 min. (table 2)

12h - 12min = 11:48 am - local mean time 11:48 - 8:20 am = 3:28 am = 55° east longitude because local noon is earlier than Greenwich Mean Time

In fact, tables 1 and 2 differ only in signs. For example, on May 14, from table 1, the correction will be + 3 min, and from the second - 3 min. Therefore, you can use, for example, Table 1 and bring the average time to true solar, and if you bring true solar to the average, then take the opposite sign of the correction. In my opinion, it is more convenient to use the first method, then you will always correct for Greenwich Mean Time and calculate the difference from 12h (true noon)

Or even easier - first calculate the difference between the true solar and mean Greenwich time, and correct the result taking into account the sign from table 2.

Remember, if at the time of local noon GMT is less than 12 hours, then you have east longitude, if more than 12 noon, then west. This method allows you to determine longitude with an accuracy of 2-3 °, and being in extreme situations, you most likely will not have a time equation table at hand to correct for the season, so only due to this the result will differ from the true one by 0 ° - 4°, depending on the season.

Definition of geographic latitude
Latitude can be determined in several ways.

Method number 1. With the help of a protractor and a plumb line. A protractor can be made from two rectangular strips fastened in a compass so that you can change the angle between them.

one). In the center of the protractor, fasten the thread with a load that plays the role of a plumb line.
2). Point the base of the protractor at the polar star.
3). Subtract 90° from the angle between the base of the protractor and the plumb line. The result will be the angle between the pole star and the horizon. Since the polar star has an angular deviation from the axis of the pole of the world by only 1 °, the angle between the polar star and the horizon will be the latitude of the area in which you are located.

Method number 2.
one). Record the length of the day between sunrise on the horizon and full sunset.
2). In the nomogram for determining the latitude, put the received length of the day on the left side, and the date on the right side. Connecting the obtained values ​​with a straight line, determine where it intersects with the middle part. This intersection will be the latitude of your area.

Nomogram for determining geographic latitude

Download from Depositfiles

6. SOLUTION OF PROBLEMS ON A TOPOGRAPHIC MAP

6.I. DEFINITION OF THE NOMENCLATURE OF THE MAP SHEET

When solving a number of design and survey tasks, it becomes necessary to search for the desired map sheet of a given scale for a certain area of ​​the area, i.e. in determining the nomenclature of a given map sheet. It is possible to determine the nomenclature of a map sheet by the geographical coordinates of the terrain points in a given area. In this case, you can also use flat rectangular coordinates of points, since there are formulas and special tables for converting them into the corresponding geographical coordinates.

EXAMPLE. Determine the nomenclature of a map sheet at a scale of 1: 10,000 according to the geographical coordinates of point M:

latitude = 52 0 48 ’ 37 ’’ ; longitude L = 100°I8′ 4I”.

First you need to determine the nomenclature of the scale map sheet

I: I 000 000, on which point M is located with given coordinates. As you know, the earth's surface is divided by parallels, drawn through 4 °, into rows, denoted by capital letters of the Latin alphabet. Point N with a latitude of 52 ° 48'37 "is located in the I4th row from the equator, located between the parallels 52 ° and 56 °. This series corresponds to the I4th letter of the Latin alphabet -N. It is also known that the earth's surface is divided by meridians, drawn through 6 °, into 60 columns. The columns are numbered in Arabic numerals from west to east, starting from the meridian with longitude I80°. The numbers of the columns differ from the numbers of the corresponding 6-degree zones of the Gauss projection by 30 units. Point M with longitude 100°18′ 4I” is located in the 17th zone, located between meridians 96° and 102°. Column number 47 corresponds to this zone. this series, and column numbers. Therefore, the nomenclature of the map sheet at a scale of 1: 1,000,000, on which point M is located, will be N-47.

Next, you need to determine the nomenclature of the map sheet, scale I: 100,000, on which point M falls. Sheets of a map of scale 1: 100,000 are obtained by dividing a sheet of a sledge of scale 1: I 000,000 into 144 parts (Fig. 8). Let's divide each side of sheet N-47 into 12 equal parts and connect the corresponding points with segments of parallels and meridians. The resulting map sheets of scale 1 : 100,000 are numbered in Arabic numerals and have dimensions: 20' in latitude and 30' in longitude. From fig. Figure 8 shows that point M with the given coordinates falls on the map sheet of scale I: 100 000 e number 117. The nomenclature of this sheet will be N-47-117.

Sheets of a map of scale I: 50,000 are obtained by dividing a sheet of a map of scale I: 100,000 into 4 parts and are designated in capital letters of the Russian alphabet (Fig. 9). The nomenclature of the sheet of this map, on which the exact M falls, will be N-47-117. In turn, the sheets of the map of scale I: 25,000 are obtained by dividing the map sheet of scale I: 50,000 into 4 parts and denoted by lowercase letters of the Russian alphabet (Fig. 9). Point M with the given coordinates falls on a map sheet of scale I: 25 000, having the nomenclature N-47-117 -G-A.

Finally, map sheets at a scale of 1: 10,000 are obtained by dividing a map sheet at a scale of 1: 25,000 into 4 parts and denoted by Arabic numerals. From fig. 9 it can be seen that point M is located on a map sheet of this scale, which has the nomenclature N-47-117-G-A-1.

The answer to the solution of this problem is placed on the drawing.

6.2. DETERMINING THE COORDINATES OF POINTS ON THE MAP

For each current topographic map you can determine its geographic coordinates (latitude and longitude) and Gaussian rectangular coordinates x, y.

To determine these coordinates, the degree and kilometer grids of the map are used. to determine the geographical coordinates of the point P, the southern parallel and the western meridian closest to this point are drawn, connecting the same minute divisions of the degree frame (Fig. 10).

The latitude B o and longitude L o of the point A o of the intersection of the drawn meridian and parallel are determined. Through a given point P, drawing lines parallel to the drawn meridian and parallel, and using a millimeter ruler measure the distances B \u003d A 1 P and L \u003d A 2 P, as well as the sizes of minute divisions of latitude C and longitude on the maps. The geographical coordinates of the point P are determined by the formulas C l

- latitude: B p = B o + *60 ’’

- longitude: L p = L o + *60’’ , measured to tenths of a millimeter.

Distances b, l, Cb, C l measured to tenths of a millimetre.

To determine the rectangular coordinates of a point R use a kilometer grid map. By digitizing this grid, coordinates are found on the map x o and o the southwest corner of the grid square where point P is located (Fig. 11). Then from the point R drop perpendiculars C 1 L and C 2 L on the sides of this square. With an accuracy of tenths of a millimeter, measure the lengths of these perpendiculars ∆X and ∆U and, taking into account the scale of the map, their actual values ​​on the ground are determined. For example, measured distance C 1 R is equal to 12.8 us, and the scale of the map is 1: 10,000. According to the scale, I mm on the map corresponds to 10 m of terrain, which means that

∆Х= 12.8 x 10 m = 128 m.

After determining the values ∆X and ∆U find the rectangular coordinates of the point P by the formulas

Xp= X o+∆ X

Yp= Y o+∆ Y

The accuracy of determining the rectangular coordinates of a point depends on the scale of the map and can be found by the formula

t=0.1* M, mm,

where M is the map scale denominator.

For example, for a map of scale I: 25 000, the accuracy of determining the coordinates X and At is t= 0.1 x 25,000 = 2500 mm = 2.5 m.

6.3. DETERMINATION OF LINE ORIENTATION ANGLES

Line orientation angles include directional angle, true and magnetic azimuths.

To determine the true azimuth of a certain line of the aircraft on the map (Fig. 12), the degree frame of the map is used. Through the starting point In this line, a line of the true meridian (dashed line NS) is drawn parallel to the vertical line of the degree frame, and then the value of the true azimuth A sun is measured with a geodetic protractor.

To determine the directional angle of a certain line DE from the map (Fig. I2), a kilometer grid of the map is used. Through the starting point D is drawn parallel to the vertical line of the kilometer grid (dashed line KL). The drawn line will be parallel to the abscissa axis of the Gaussian projection, i.e., to the axial meridian of the given zone. The directional angle α de is measured by geodetic transport relative to the drawn line KL. It should be noted that both the directional angle and the true azimuths are counted, and therefore measured clockwise relative to the initial direction to the line being oriented.

In addition to directly measuring the directional angle of a line on the map using a protractor, you can determine the value of this angle in another way. For this definition, the rectangular coordinates of the start and end points of the line are (X d, Y d, X e, Y e). The directional angle of a given line can be found by the formula

When performing calculations using this formula using a microcalculator, it should be remembered that the angle t = arctg (∆y / ∆x) is not a directional angle, but a tabular angle. The value of the directional angle in this case must be determined taking into account the signs ∆X and ∆Y according to the known reduction formulas:

Angle α lies in the first quarter: ∆Х>0; ∆Y>0; α=t;

Angle α lies in the II quarter: ∆Х<0; ∆Y>0; α=180o-t;

Angle α lies in the III quarter: ∆X<0; ∆Y<0; α=180 o +t;

The angle α lies in the IV quarter: ∆Х>0; ∆Y<0; α=360 o -t;

In practice, when determining the reference angles of a line, one usually first finds its directional angle, and then, knowing the declination of the magnetic needle δ and the convergence of the meridians γ (Fig. 13), they pass to the true to the magnetic azimuths using the following formulas:

A=α+γ;

A m \u003d A-δ \u003d α + γ-δ \u003d α-P,

where P=δ-γ - the total correction for the declination of the magnetic needle and the convergence of the meridians.

The quantities δ and γ are taken with their signs. The angle γ is measured from the true meridian to the magnetic one and can be positive (east) and negative (west). The angle γ is measured from the degree frame (true meridian) to the vertical line of the kilometer grid and can also be positive (east) and negative (west). In the diagram shown in fig. 13, the declination of the magnetic needle δ is east, and the convergence of the meridians is west (negative).

The average value of δ and γ for a given map sheet is given in the southwest corner of the map below the design frame. The date of determining the declination of the magnetic needle, the magnitude of its annual change and the direction of this change are also indicated here. Using the indicated information, it is necessary to calculate the magnitude of the declination of the magnetic needle δ on the date of its determination.

EXAMPLE. Declension for 1971 east 8 about 06 '. Annual change declination west 0 o 03 '.

The value of the declination of the magnetic needle in 1989 will be: δ=8 o 06'-0 o 03'*18=7 o 12'.

6.4 DETERMINATION OF POINT HEIGHTS FROM HORIZONTALS

Elevation of a point located on a horizontal line is equal to the elevation of this horizontal line. It should be remembered that every fifth contour line has a digitization on the map, and for the convenience of determining the marks, the digitized contour lines are drawn with thickened lines (Fig. 14, a). Horizontal marks are signed at line breaks so that the base of the numbers is directed towards the slope.

More general is the case when the point is between two contours. Let the point P (Fig. 14, b), the elevation of which is required to be determined, be located between the horizontals with the marks of 125 and 130 m. . As can be seen from the vertical section along the line AB (Fig. 14, c), the value of ∆h represents the excess of the point P above the minor horizontal (125 m) and can be calculated by the formula

∆ h= * h ,

where h is the height of the relief section.

Then the mark of the point P will be equal to

H R = H a + ∆h.

If the point is located between contour lines with the same marks (point M in Fig. 14, a) or inside a closed horizontal line (point K in Fig. 14, a), then the mark can only be determined approximately. In this case, it is considered that the mark of the point is less than or greater than the height of this horizon and half the height of the relief section, i.e. 0.5h (for example, N m = 142.5 m, H k = 157.5 m). Therefore, the marks of the characteristic points of the relief (the top of the hill, the bottom of the basin, etc.), obtained from measurements on the ground, are written out on plans and maps.

6.5 DETERMINATION OF THE SLOPE BY THE SCHEDULE OF LAYING

The steepness of the slope is the angle of inclination of the slope to the horizontal plane. The larger the angle, the steeper the slope. The value of the angle of inclination of the slope v is calculated by the formula

V=arctg(h/ d),

where h is the height of the relief section, m;

d-layout, m;

The laying is the distance on the map between two adjacent horizontals; the steeper the slope, the less the laying.

To avoid calculations when determining the slopes and steepness of slopes according to a plan or map, in practice they use special graphs called laying graphs. The laying graph is a function graph d= n* ctgν, the abscissas of which are the values ​​of the angles of inclination, starting from 0°30´, and the ordinates are the values ​​of the occurrences corresponding to these angles of inclination and expressed on the scale of the map (Fig. 15,a).

To determine the steepness of the slope with a solution of a compass, take the corresponding position from the map (for example, AB in Fig. 15, b) and transfer it to the laying chart (Fig. 15, a) so that the segment AB is parallel to the vertical lines of the graph, and one leg of the compass was located on the horizontal line of the graph, the other leg - on the curve of occurrences.

The slope slope values ​​are determined using the digitization of the horizontal scale of the graph. In the example under consideration (Fig. 15), the slope slope is ν= 2°10´.

6.6. DESIGNING A LINE OF A GIVEN SLOPE

When designing roads and railways, canals, various engineering communications, the task arises of plotting the route of a future structure with a given slope on a map.

Let on a map of scale 1:10000 it is required to outline the road route between points A and B (Fig. 16). To ensure that its slope throughout its entire length does not exceed i=0,05 . The height of the relief section on the map h= 5 m.

To solve the problem, the amount of laying is calculated corresponding to the given slope and section height h:

Then express the location on the scale of the map

where M is the denominator of the numerical scale of the map.

The value of laying d´ can also be determined from the laying schedule, for which it is necessary to determine the angle of inclination ν corresponding to the given slope i, and measure the laying for this angle of inclination with a compass solution.

The construction of the route between points A and B is carried out as follows. With a compass solution equal to the laying d´ \u003d 10 mm, an adjacent horizontal is detected from point A and point 1 is obtained (Fig. 16). From point 1, the next horizontal line is marked with the same compass solution, getting point 2, and so on. By connecting the obtained points, draw a line with a given slope.

In many cases, the terrain allows you to outline not one, but several options for the route (for example, Options 1 and 2 in Fig. 16), from which the most appropriate one is selected for technical and economic reasons. So, for example, from two options for a route drawn approximately in under the same conditions, the option with a shorter length of the designed route will be selected.

When constructing a route line on the map, it may turn out that from some point on the route the compass opening does not reach the next horizontal line, i.e. the calculated laying d´ is less than the actual distance between two adjacent horizontals. This means that in this section of the route, the slope of the slope is less than the specified one, and the design is expensively regarded as a positive factor. In this case, this section of the route should be drawn along the shortest distance between contour lines towards the end point.

6.7. DETERMINATION OF THE BOUNDARY OF THE DRAINAGE AREA

catchment area, or a swimming pool. A section of the earth's surface is called, from which, according to the conditions of the relief, water must flow into a given drain (hollow, stream, river, etc.). The contouring of the catchment area is carried out taking into account the contours of the terrain. The boundaries of the catchment area are watershed lines that intersect horizontal lines at right angles.

Figure 17 shows a hollow through which the stream PQ flows. The basin boundary is shown by the dotted line HCDEFG and drawn along the watershed lines. It should be remembered that watershed lines are the same as water collection lines (thalwegs). Cross horizontals in places of their greatest curvature (smaller radius of curvature).

When designing hydraulic structures (dams, locks, embankments, dams, etc.), the boundaries of the catchment area may change their position somewhat. For example, let it be planned to build a hydraulic structure (AB-axis of this structure) on the site under consideration (Fig. 17).

From the end points A and B of the designed structure, straight lines AF and BC are drawn to the watersheds, perpendicular to the horizontals. In this case, the BCDEFA line will become the watershed boundary. Indeed, if we take points m 1 and m 2 inside the pool, and points n 1 and n 2 outside it, then it is difficult to notice that the direction of the slope from points m 1 and m 2 goes to the intended structure, and from points n 1 and n 2 bypasses him.

Knowing the catchment area, the average annual rainfall, the conditions of evaporation and the absorption of moisture by the soil, it is possible to calculate the power of the water flow for the calculation of hydraulic structures.

6.8. Building a terrain profile in a given direction

A line profile is a vertical section along a given direction. The need to build a terrain profile in a given direction arises in the design of engineering structures, as well as in determining the visibility between terrain points.

To build a profile along the line AB (Fig. 18, a), by connecting points A and B with a straight line, we obtain the points of intersection of the straight line AB with horizontals (points 1, 2, 3, 4, 5, 6, 7). These points, as well as points A and B, are transferred to a strip of paper, attaching it to the line AB, and sign the marks, defining them horizontally. If the line AB intersects a watershed or catchment line, then the marks of the points of intersection of the line with these lines will be determined approximately by interpolation along these lines.

It is most convenient to build a profile on graph paper. The construction of the profile begins with the fact that a horizontal line MN is drawn, onto which the distances between the intersection points A, 1, 2, 3, 4, 5, 6, 7, B are transferred from a strip of paper.

The conditional horizon is chosen so that the profile line does not intersect anywhere with the conditional horizon line. For this, the conditional horizon mark is taken 20-20 m less than the minimum mark in the considered series of points A, 1, 2, ..., B. Then a vertical scale is chosen (usually, for greater clarity, 10 times larger than the horizontal scale, i.e. map scale) . At each of the points A, 1, 2. ..., B on the MN line, the perpendiculars are restored (Fig. 18, b) and the marks of these points are laid on them in the accepted vertical scale. By connecting the obtained points A´, 1´, 2´, ..., B´ with a smooth curve, a terrain profile along the line AB is obtained.

With such concepts as longitude and latitude, many of us met in childhood thanks to the adventure novels of Stevenson and Jules Verne. People have been studying these concepts since ancient times.


In an era when perfect navigational instruments did not exist in the world, it was the geographical coordinates on the map that helped sailors determine their location in the sea and find their way to the desired land areas. Today, latitude and longitude are still used in many sciences and allow you to accurately determine the position of any point on the earth's surface.

What is latitude?

Latitude is used to set the location of an object relative to the poles. At the same distance from and passes the main imaginary line of the globe - the equator. It has zero latitude, and parallels stretch on both sides of it - similar imaginary lines that conditionally cross the planet at regular intervals. To the north of the equator are the northern latitudes, to the south, respectively, the southern ones.

The distance between the parallels is usually measured not in meters or kilometers, but in degrees, which allows you to more accurately determine the position of the object. There are 360 ​​degrees in total. Latitude is measured north of the equator, that is, points lying in the Northern Hemisphere have a positive latitude, and those located in the Southern Hemisphere have a negative one.

For example, the north pole lies at a latitude of +90°, the south pole at -90°. Additionally, each degree is divided into 60 minutes, and minutes into 60 seconds.

What is longitude?

To find out the location of an object, it is not enough to know this place on the globe relative to the south or north. In addition to latitude, longitude is used for a complete calculation, which sets the position of the point relative to east and west. If in the case of latitude the equator is taken as the basis, then longitude is calculated from the zero meridian (Greenwich), passing from the North to the South Pole through the London area of ​​Greenwich.

On the right and left sides of the Greenwich meridian, ordinary meridians are drawn parallel to it, which meet each other at the poles. East longitude is considered positive, and west longitude is negative.


Like latitude, longitude has 360 degrees divided into seconds and minutes. To the east of Greenwich is Eurasia, to the west - South and North America.

What are latitude and longitude for?

Imagine that you are sailing on a ship lost in the middle of the ocean, or moving through the endless desert, where there are no signs and indicators at all. How could you explain your location to rescuers? It is latitude and longitude that help to find a person or other object anywhere in the world, wherever he is.

Geographic coordinates are actively used on maps of search engines, in navigation, on ordinary maps. They are present in geodetic instruments, satellite positioning systems, GPS navigators and other tools needed to determine the location of a point.

How to set geographic coordinates on the map?

To calculate the coordinates of an object on the map, you must first determine in which of the hemispheres it is located. Next, you should find out between which parallels the desired point is located, and set the exact number of degrees - usually they are written on the sides of the geographical map. After that, you can proceed to the determination of longitude, first establishing in which of the hemispheres the object is located relative to Greenwich Mean Time.


Determination of degrees of longitude is carried out similarly to latitude. If you need to find out the location of a point in three-dimensional space, its height relative to sea level is additionally used.

There are many different coordinate systems. All of them are used to determine the position of points on the earth's surface. This includes mainly geographic coordinates, flat rectangular and polar coordinates. In general, it is customary to call coordinates angular and linear quantities that define points on a surface or in space.

Geographic coordinates are angular values ​​- latitude and longitude, which determine the position of a point on the globe. Geographic latitude is the angle formed by the plane of the equator and a plumb line at a given point on the earth's surface. This angle value shows how far a particular point on the globe is north or south of the equator.

If the point is located in the Northern Hemisphere, then its geographical latitude will be called northern, and if in the Southern Hemisphere - southern latitude. The latitude of points located on the equator is zero degrees, and at the poles (North and South) - 90 degrees.

Geographic longitude is also an angle, but formed by the plane of the meridian, taken as the initial (zero), and the plane of the meridian passing through the given point. For the uniformity of the definition, it was agreed to consider the meridian passing through the astronomical observatory in Greenwich (near London) as the initial meridian and call it Greenwich.

All points located to the east from it will have eastern longitude (up to the meridian of 180 degrees), and to the west of the initial one - western longitude. The figure below shows how to determine the position of point A on the earth's surface if its geographical coordinates (latitude and longitude) are known.

Note that the difference in longitudes of two points on Earth shows not only their relative position with respect to the zero meridian, but also the difference in these points at the same moment. The fact is that every 15 degrees (24th part of the circle) in longitude is equal to one hour of time. Based on this, it is possible to determine the difference in time at these two points by geographical longitude.

For example.

Moscow has a longitude of 37°37′ (East), and Khabarovsk -135°05′, that is, lies to the east of 97°28′. What time do these cities have at the same moment? Simple calculations show that if it is 13:00 in Moscow, then it is 19:30 in Khabarovsk.

The figure below shows the design of the sheet frame of any map. 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 signed.

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 latitude scale to the right or left. In our example, point M has a latitude of 45°31’30”.

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

Drawing a point on a topographic map according to given geographical coordinates.

Drawing a point on the map according to the given geographical coordinates is carried out in the reverse order. First, the indicated geographical coordinates are found on the scales, and then parallel and perpendicular lines are drawn through them. Intersecting them on will show the point with the given geographic coordinates.

Based on the book "The map and the compass are my friends."
Klimenko A.I.

Instruction

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

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

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

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

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

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

Instruction

Instruction

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

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

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

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

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

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

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What is tundra?

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

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

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

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

Flora and fauna

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

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

The northernmost point of Africa

The most extreme point of the African continent has the following: 37° 20′ 28″ north latitude and 9° 44′ 48″ east longitude. Thus, we can state that this point is located on the territory of one of the small states in North Africa - in Tunisia.

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

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

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

Other names

At the same time, the cape, which is the northernmost point of the African continent, has other names. So, at a time when Tunisia was a French colony, the name was quite common in European countries, which is a translation of the Arabic original into French: it was called “Cap Blanc”, which in French also meant “white cape”. However, the primary source of such a name was still the Arabic name of this geographical point.

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