How is the relief depicted on the map? Relief image. Question. How land relief is depicted on maps

Image of elevation marks on the map

Relief depicted on topographic maps using contour lines - closed curved lines of equal height above sea level.

Definition 1

Horizontal– a line of equal absolute heights of the earth’s surface.

The drawing and relative position of the horizontals shows the relative position, relationship and shape of the irregularities of the depicted surface. Horizontals have the following characteristics: section height and laying.

Definition 2

Contour section height– distance (in height) between adjacent cutting surfaces.

The height of the section is determined by the nature of the terrain and the scale of the map. This characteristic is indicated on each sheet of the map in text form under the frame on the south side.

Definition 3

Laying out contours– the distance on the map between two adjacent contour lines, depending on the height of the relief section on a given map and the steepness of the slope. the distance between adjacent contour lines on the map.

This characteristic clearly shows the steepness of the slope: the shallower the slope, the greater the angle of inclination.

Types of contours

There are the following types of contour lines on the map:

• basic or solid. They are drawn in solid lines in accordance with the established section height;
• half horizontals, or semi-horizontals, which are drawn in broken lines through $½$ of the selected section height and serve to display important details.
• auxiliary horizontal lines, which show even finer features of the relief and are applied approximately ¼ of the section height with broken lines with short links
• thickened horizontals- these are the main horizontal lines that correspond to five times the height of the section. In accordance with the name, they are drawn thicker and used for easier reading of cards.

Example 1

If at the bottom of the map there is the inscription “Solid contour lines are drawn through $100$ m,” this means that thin solid lines—solid contour lines—are drawn every $100$ m, and thick contour lines are drawn every $500$ m.

Selecting the section height

As a rule, the height of the section is selected in accordance with the map scale and type of terrain. For flat and hilly terrain, the section height is calculated as $0.02$ of the map scale. For high mountain areas, the cross-sectional height is taken to be twice as high, i.e. $0.04$ scale value. For flat areas, on the contrary, the height of the section is half of the normal one, i.e. $0.01$ scale value.

Example 2

On the map of the Moscow region (flat terrain) on a scale of $1:100\000$, solid horizontal lines are drawn through $20$ meters, and on the map of Nepal (high mountain region) on a scale of $1:100\000$ - through $40$ meters. On a map of a similar scale depicting the flat-flat Tavdinsky district of the Sverdlovsk region, the main horizontal lines will pass through $10$ meters.

At a map scale of $1:10\000$, for flat terrain the contour lines will be drawn through $2$ meters, for high mountain terrain – through $4$ meters, and for flat terrain – through $1$ meter.

Determining the direction of slopes

Contour lines show only the heights of objects and their relative positions on the map. Closed lines often make it difficult to distinguish the type of landform. So, on a map, a ridge and a valley, depicted only using contour lines, can look the same. After all, these forms distinguish only the directions of the slopes. Therefore, in addition to contour lines, dashes are applied to the map.

Definition 4

Bergstrich- a short line that is placed on the horizontal lines perpendicular to it, usually at the place of the bend, and indicating on the map the fall of the slope.

In addition to the berghstrokes, the direction of the slopes on the map can be determined by the marked elevations:

• contour marks - digital signatures along the contours, showing the height above sea level in meters. Moreover, the top of the numbers is always applied towards the higher part of the slope.
• elevation marks – digital signatures of characteristic points of the terrain (tops of hills and watersheds, water edge, lowest points of valleys).

The accuracy in the signature of elevation marks is determined by the scale:

• $1:100\000$ and larger – up to $0.1$ m
• $1:200\000$ and smaller – up to $1$ m.

Conventional signs of relief elements

There is a system of special symbols for objects and relief details that cannot be depicted with horizontal lines. These include cliffs, rocks, screes, ravines, gullies, shafts, road embankments and excavations, mounds, pits, karst funnels. Signs of natural relief formations and accompanying signatures (relative heights or depths in meters) are brown, artificial ones are black.

Some natural objects are also shown in black: clusters of stones or individual large stones, rock outcrops, grottoes, tunnels.

Mountain maps also show passes, indicating the altitude and time of the area. The relief of firn fields and glaciers and accompanying signatures and signs are shown on maps as blue contours.

Features of relief images on small-scale maps

On maps of scale $1:500\000$ and $1:1\000\000$, the relief is also depicted using contour lines and symbols. However, unlike larger scales, the image is more generalized. They show its general features - structure, degree of dissection and basic forms. The main section of contour lines for flat areas is $50$ m, for mountainous areas – $100$ m. In addition, on maps of scale $1:1\000\000$ for areas at an altitude of more than $1000$ m above sea level, a section height of $200$ m is used.

Conventional signs of relief objects are shown to the extent that they are necessary for characterization or orientation on the terrain. In this case, smaller versions of standard signs are used.

In addition, mountainous terrain on small-scale maps is shown additionally by layer-by-layer coloring in elevation steps and by shading. Layer-by-layer painting is done with orange paint of various tones with increasing intensity as the height increases. The tone of the paint can change through $400$, $600$ or $1000$ m based on the absolute elevation of the depicted area. The scale used is applied in the same way as the cross-section of contour lines under the map frame on the south side.

Shading is the addition of shadows to images of the slopes of the main forms of mountainous relief, which contributes to a more voluminous perception of the relief. Moreover, the tone of the wash also indicates the steepness and height of the slope. Using a wash, mountain ranges, canyons, and valleys are clearly depicted.

Relief is a set of irregularities in the real physical surface of the Earth. According to their origin, relief elements are divided into natural And artificial. On the topography

On technical maps, relief elements of natural origin are usually denoted in brown, and elements of artificial origin - in black. The relief is depicted using conventional signs, heights and contour lines (the main method). Conventional signs are used to depict relief elements that cannot be displayed using contour lines (cliffs, ravines, gullies, slopes, retaining walls, etc.). On geographic maps, the relief of the surface and bottom of seas and oceans is depicted using washing, this method is not used when creating topographic maps. However, when using computer technologies for creating topographic maps, depicting the relief on them using hillshading does not pose any problem.

Basin

Rice. 3.14.

If we cut any shape of the earth’s surface with a horizontal plane (Fig. 3.14), we will get a certain curve, all points of which will have the same height value, so we can give two equivalent definitions of the horizontal:

• 1) horizontal - a curve obtained by a section of the earth’s surface horizontal flat;
• 2) horizontal - an imaginary curve, all points of which have the same height value.

GOST gives the following definition: “Horizontal is a line of equal heights on a map.”

The height of the relief section with horizontals is the distance between adjacent cutting planes (or level surfaces) when depicting the relief with horizontals. Layout - the distance on a plan or map between two adjacent contour lines in a given direction. The laying of the slope is the laying in the direction normal to the horizontals.

At the same height of the cross-section of the relief with horizontals, the lower the slope, the greater the steepness of the slope - the angle between the direction of the slope and the horizontal plane at a given point

(Fig. 3.15). Consequently, the steepness of the slopes can be judged by the depth of the slope. In Fig. 3.15 laying down the slope (1 X more than the laying of a ramp D 2 , therefore, the corresponding slope steepness is less than the slope steepness for b 2.

Rice. 3.15. Steepness and laying

To make it easier to determine the magnitude of the angles of inclination or slopes (the slope is called the tangent of the angle of inclination), use graphs of the location, on which the angle of inclination V or the magnitude of the slope is indicated along the horizontal axis And, and along the vertical - the corresponding location on a given scale (Fig. 3.16).

If you compare images of a mountain and a basin in which they are shown using contour lines, the images will not differ. To distinguish them and to indicate the direction of slopes on plans and maps, berg strokes are used - short strokes drawn from the horizontal image down in the direction of the slope (see Fig. 3.14).

The height of the relief section depends on the complexity of the relief (the relief is considered more complex, the steeper the slopes) and, for example, for plans at a scale of 1:500 it is taken to be equal to 0.25, 0.5, 1.0 m, and for a scale of 1:5000 - 1.0, 2.0, 5.0 m.

The main forms of natural relief are: mountain(hill, hill), basin, ridge, valley(log, valley, valley), slope, saddle(Fig. 3.17). A curve that sequentially connects ridge points with the highest altitude values ​​is called watershed. The curve that sequentially connects the points of the valley with the lowest height values ​​is called a thalweg.

For clarity, when depicting the relief on plans and maps, various types of contour lines are used, namely:

• basic, sections of the relief corresponding to the accepted height and drawn in the form of a solid line with a thickness of 0.12 mm of brown color;
• main thickened, which serve as the main horizontal lines, the heights of which are multiples of four or five sections

relief; their thickness is assumed to be 0.3 mm. For example, when cutting a relief And = 2 m the main thickened horizontal lines will be horizontal lines with heights of 10, 20, 30 m, etc.;

Rice. 3.17.

A- mountain; 6 - basin; V- slope; G- watershed, ridge; d- valley, ravine;

e- saddle

• additional, also called semi horizontal and drawn through 0.5 sections of the relief in order to depict relief features that are not expressed using the main contour lines; they are dashed lines 0.12 mm thick;
• auxiliary, carried out through 0.25 sections of the relief, for which reason they are also called quarter-horizontals.

To be more precise, then multiplicity of thickened horizontal lines for relief sections of 1, 2 or 5 m there are five sections, and for sections of 0.25, 0.5 or 2.5 m - four sections.

In order to be able to determine the heights of points on the earth’s surface from maps and plans, the heights of the contour lines are evenly signed over the entire area of ​​each sheet of the plan or map. In this case, the numbers indicating the horizontal height are located head up the slope.

To make it easier to determine the heights of contour lines over the entire area of ​​a sheet of plan or map, mark the marks of some points, first of all the most characteristic ones: points of local minima or maxima, saddle points, etc.

To preserve information about the relief of a particular area, humanity uses topographic maps. Horizontals - closed curved lines characterized by equal height above sea level - will allow you to convey the completeness of information. The following definitions help clarify such subtleties:

1. Horizontal - a line of equal absolute heights of the earth's surface. The pattern and location of the horizontal lines relative to each other allows you to determine the connection and shape of the unevenness of the territory. The characteristics of such a concept as horizontals are the height of the section and the location.

2. The height of the section is the distance separating adjacent secant surfaces. Here it is important to consider compliance with the nature of the terrain and the scale of a particular map. For better understanding, this information is contained in text form on each sheet of the map, framed on the south side.

3. Layout is the distance from one to another adjacent horizontal line plotted on the map. The height of the cross-section of a particular relief, as well as the degree of steepness of the slope, plays a fundamental role in understanding the map. More precisely, the greater the angle of inclination, the less the laying.

Horizontals: division into types

The following types of contours are used for drawing on a map:

• main (solid), drawn using solid lines (corresponding to the height of the section);
• semi-horizontals (half) showing important details, having the form of broken lines (through 1/2 of the section height);
• clarifying information about the details of the relief, auxiliary horizontal lines drawn through 1/4 of the section height in the form of short dashed lines;
• thickened horizontal lines corresponding to five times the section height make the maps easier to read.

The inscription at the bottom of the map indicating solid contours drawn every 100m means that solid thin contours are repeated every 100m, and thickened analogues - every 500m.

How to choose a section height

When choosing a section height, the type of terrain and map scale are taken into account. For both flat and hilly areas, the calculation of the section height provides for 0.02 of the scale value. Regarding high mountain areas, there is a twofold increase in the section height (0.04 scale). Drawing of flat-flat places on the map is characterized by a twofold decrease in the height of the section (0.01 scale).

The flat terrain of the Moscow region is mapped at a scale of 1:100,000. In this case, solid lines are drawn every 20 m. For high mountain Nepal, where the map scale is 1:100,000, contour lines are plotted at 40m intervals. With the same scale of a map of a certain flat-flat area, repetition of contour lines is observed every 10 m.

Conclusion: the scale of the map of flat areas provides for drawing contour lines every 2 meters, for high mountain areas - every 4 meters, for flat-flat surfaces - every meter.

Slope directions: features of definition

With the help of contour lines, it is possible to obtain information about the location of objects and their height. Since the application using horizontal lines, both ridge and valley, is practically the same, you have to use not only closed lines. Here, such additions to horizontal lines as berghstrokes are used, which make it possible to distinguish, in addition to the direction of the slopes, also the most complex forms of relief.

4. The concept of a bergstroke means a short line standing (at the bend) perpendicular to the horizontal. This is how the slope is indicated to fall. Understanding the direction of the slopes will be provided by berg strokes, as well as elevation marks of different types:

• Contour marks, which have the form of digital signatures written along the contours and give an idea of ​​the height above sea level. Moreover, the upper part of the numbers is in the area where the height of the slope is the highest.
• Elevation marks are digital signatures on watersheds, edges, hilltops, and the lowest places in valleys.

The accuracy of such signatures depends on the selected scale:

• 1: 100,000 and above – up to 0.1m;
• 1: 200,000 or less – up to 1 m.

Relief elements conveyed through symbols

To plot specific relief details on a map, symbols of a special type are used. In this regard, it is worth mentioning screes, cliffs, rocks, gullies, ravines, shafts, recesses, mounds, pits, karst-type funnels, etc. Moreover, the signs of such formations are supplemented by signatures regarding height or depth. What is also important: objects of natural origin are depicted with brown paint, and artificial ones - with black color. The second option includes: rock formations, grottoes, tunnels, rock outcrops, etc. In addition, mountain maps display passes, complete with elevation and time in place. To apply firn fields, glaciers and additional signs, blue paint is used.

Characteristic features of the relief on a small-scale map

Drawing relief on maps with a scale of 1:500 00 and 1:1 000 000 is done using contour lines and symbols. True, here there is a generalized nature of the application, when only the structure, level of dissection, and basic forms are shown.

The frequency of the horizontal section varies according to the type of surface:

• for plains – 50m;
• for mountainous areas – 100m.

And if the altitude above sea level exceeds 1000m, then at a scale of 1: 1,000,000, the emphasis is on a section height of 200m.

The scope of applying symbols for certain objects is regulated according to the need for orientation on the ground. Moreover, the choice is made in favor of smaller versions of signs.

When plotting mountainous terrain on a small-scale map, elevation steps and shading are shown using layer-by-layer paint. As the height of the relief increases, there is a transition from orange of different shades to brown of variable intensity. Changes in tone take place every 400, 600, 1000 m (corresponding to the absolute altitude of the given territory). To apply the scale of interest, they are oriented in the same way as in the case of the section of horizontal lines indicated on the map on the south side (under the frame).

Volumetric perception of the relief is provided by adding shadows on the slopes of mountainous terrain. Regarding the steepness and height of the slope, judge by the tone of the shade, which will provide a visual representation of valleys, canyons, mountain ranges, etc.

Relief is a set of spatial forms (irregularities) of the earth's surface. Relief is one of the most important elements of the geographical environment. It has a significant impact on the redistribution of heat and moisture, the nature of the migration of chemical elements and, consequently, on the properties of soils and vegetation, thus determining the landscape features of the territory. On the other hand, the location of settlements, communication routes, industrial and energy facilities, as well as the conditions of agricultural production (slope exposure, soil erosion, the possibility of mechanical cultivation of the land, etc.) are in many cases determined by the nature of the relief of the earth's surface. During combat operations, taking into account the features of the terrain is necessary to determine the possibilities of open movement, camouflage, traffic conditions, etc.

Method of depicting relief on a map. The task of displaying relief on maps is very difficult, since three-dimensional, convex and concave shapes, their heights, sizes, and slope steepness must be shown on a flat sheet of paper. The relief image must be measurable.

On topographic maps, the relief is depicted using contour lines, which are supplemented by indicating the heights of characteristic points of the area and symbols of individual elements and forms of relief.

Horizontal- is an imaginary line on the physical surface of the Earth, all points of which have the same height above sea level, i.e. the absolute height along each horizontal line is constant. If you cut some form of relief with horizontal planes, as shown in Figure 30, A, each section line will have a constant height; it is thus horizontal.

Rice. 30. The principle of forming contours

Section planes are constructed at equal intervals in height, and the resulting section lines are projected with vertical rays onto a common plane (map). This is how a relief image is obtained on the map with a system of contour lines in the form of closed curved lines (Fig. 30, B). The outlines of the contour lines are obviously determined by the external appearance of the relief forms, and their number on a given map is determined by the greatest difference in heights in the mapped area.

Rice. 31. Elements of the ramp (A). Reflection of ramp elements using contour lines on the map (B)

The difference in height of two adjacent main contour lines is called relief section height. Figure 31, A shows a section of a section of the earth's surface with a vertical plane. The secant horizontal surfaces are drawn through 10 m in height and have marks of 90, 100, 110, 120 and 130 m. The section height h is 10 m. The section lines of the earth's surface by horizontal planes are then projected onto a common horizontal surface (Fig. 31, B), those. map. The spaces on the map between two adjacent contour lines are called depth d. The location is always less than the distance S between the same points on the slope (slope).

The steepness of the slope is expressed through tilt angleα. At a constant section height h, a change in the steepness of the slope entails a change in the laying: the greater the angle of inclination, the smaller the laying on the map. The connection between the elements of the slope is expressed mathematically: d = S cosα ; h = S sinα ; h = d tan α ; d = h tanα.

The amount of inclination of the earth's surface (steepness of the slope) is often characterized not by the angle α, but by the slope i. The slope is the ratio of the elevation of the terrain to the horizontal extent at which it is observed: i =h/d= tanα. Slope is usually expressed as a decimal fraction in thousandths (or percentage). So, with a road slope of 0.015, on a segment of 1000 m the rise will be 15 m. The slope of the railway track in difficult sections is shown on special signs mounted on poles near the road.

The detail of the relief image on the map depends on the height of the section. With rare cutting planes, i.e. at a high cross-sectional height, a number of features of the shapes of the earth's surface will not be reflected. For example, in the lower part of the slope shown in Figure 31, A, there are highs and lows that are not shown on the map. Therefore, on detailed maps the section height is taken smaller, and with a decrease in scale the section height increases.

On Soviet topographic maps, standard relief cross-sectional heights are used. For example, when mapping flat and hilly areas, the following section heights are accepted: on a map of scale 1:25,000 - 5 m, 1:50,000 - 10 m, 1:100,000 - 20 m. Contours with a standard height difference are called basic. Horizontal lines are drawn with solid thin brown lines.

An indication of the cross-sectional height accepted on this map is given under the linear scale of the map in the form of the phrase “Solid horizontal lines are drawn through...”.

The absolute heights of individual horizontal lines, i.e. their marks are signed in special horizontal breaks. In this case, the top of the numbers is directed towards increasing the slope. On maps, for greater clarity, every fifth horizontal line is thickened, the height of which always corresponds to five times the height of the relief section on a given map.

On gentle slopes, sometimes there are important relief details (depressions, elevations, ledges), which with a standard section height will not be reflected on the map. An example of this is the lower section of the slope between horizontal 90 and 100 m in Figure 31, L. In these cases, additional cutting planes are introduced between the main cutting planes and the resulting horizontal lines are shown on the map as broken lines. Typically, additional sections are drawn in the middle between the main ones and the resulting horizontal lines are called semi-horizontals. If they are not enough to identify the features of the relief, auxiliary horizontal lines are drawn (about a quarter of the section height), indicated by even shorter strokes.

Rice. 32. Image of the relief with horizontal lines: main (90, 100, 110 m), additional (95 m), auxiliary (98 m)

The section of the slope between the main horizontal lines of 90 and 100 m in Figure 31, B looks long and gentle, although in reality it is complicated by an increase. In the enlarged drawing of the same area (Fig. 32), additional cutting planes were constructed and a semi-horizontal of 95 m and an auxiliary horizontal of 98 m were drawn, which displayed the structure of the slope on the map in more detail.

Elevations are called the signatures of absolute heights in meters of the highest points of the peaks, the lowest points of the depressions, and points at the bends of the slopes. Often marks are given for landmarks (road intersections, individual buildings, etc.). The absolute height of the water surface in a river or lake is called water's edge, its value is indicated on the coastline of water bodies.

To show on maps a number of relief forms that are not expressed by contour lines on the map scale, symbols are used. These are images of mounds, rock outcrops, isolated stones, landslides, screes of sand, stones or rubble, as well as ravines, karst funnels, gullies, steep cliffs and turf ledges. In addition, blue signs characterize firn fields, glaciers, ice cliffs and other manifestations of modern glaciation.

Some of these signs are accompanied by quantitative indicators. For example, the height of cliffs, width and depth of ravines in meters are given. Artificial landforms (embankments, excavations, etc.) are shown on maps with black symbols; the image of natural relief is shown in brown.

Basic elements and forms of relief. The relief of the earth's surface is composed of slopes (slopes) of various shapes and steepness; Slopes that are straight and curved in plan are schematically distinguished, as well as slopes that are straight (flat) and slopes that are curved in profile. Their images on the map differ in the shape of the contours and the nature of the alternation of deposits of different sizes (Fig. 33).

Rice. 33. Schematic representation of the main forms of slopes with horizontal lines

When two slopes meet, relief inflection lines appear: watershed and drainage lines, the edge and the bottom of the slope. Watershed line formed on a convex form of relief when two slopes of opposite directions meet; on it there is a transition from ascent to descent. drainage line, or thalweg, - line of inflection of slopes in the opposite direction on a concave form of relief; there is a transition from descent to ascent. Brovka- this is the line where a horizontal platform or a gentle slope meets a steeper slope. Sole- this is the line of transition from a steeper slope to a less steep one or to a horizontal platform. On the edge and sole, the steepness and not the direction of the slope changes. In nature, relief inflection lines are usually curved and inclined.

Simple combinations of slopes form simple landforms. These include positive forms that rise above the surrounding area - a mountain (hill), a simple ridge (ridge), a ledge and negative, concave forms - a depression, a valley (hollow, beam), a slope deflection.

Mountain- a dome-shaped rise with more or less steep slopes, in the lower part bordered by a base - the line of transition of the slopes of the mountain to the surrounding area. A mountain, as well as a smaller landform - a hill, is depicted by closed horizontal lines with berg strokes directed outward from them (Fig. 34). The depression is formed by more or less steep closed slopes going down from the edge and ends at the bottom with the lowest point of the depression. Small shallow depressions are often called saucers, and cone-shaped depressions are called funnels. The depression, like the mountain, is depicted on the map with closed horizontal lines, but the berg strokes from the horizontal lines are directed inside the depression (see Fig. 34).

Rice. 34. Representation of landforms of a site using contour lines, elevation marks and symbols

simple ridge formed by two slopes going up from the base and meeting along the watershed line. On the map, the ridges are depicted as a system of elongated V-shaped horizontal lines, the convexities of which face down the slope. The valley, like the hollow and the ravine, is bounded by two slopes going down from the edges and giving a thalweg line when they close. This is an elongated, concave shape descending in one direction. A constant watercourse flows along the bottom of the valley. The valley (like the ravine) is depicted on the map by a system of V-shaped contours, convexly facing up the slope.

Figure 35 shows a perspective image of a section of a river valley with the designation of its parts, a cross section of the valley, and below is a schematic representation of the horizontal strip of the river valley along the profile line. Sparse horizontal lines on the surface of the terrace are replaced by denser horizontal lines in section 6-5-4. A slope and a horizontal area, such as a floodplain, form a bend in the slope (section 5-4-3); in this case, after the thickening of the contours, their noticeable rarefaction follows.

Rice. 35. River valley section

The forms discussed above do not occur in nature in isolation; they are usually combined, transforming into one another and forming more complex complexes of forms. For example, when two valleys or hollows cut into a ridge or ridge from opposite sides, a trough called a saddle is formed on the watershed, the lowest point of which is a pass.

So, depicting the relief with horizontal lines allows you to recognize the shapes and elements of the relief from the map, as well as obtain a number of its quantitative characteristics. As the map scale decreases, the detail of the relief image decreases, as the section heights increase, images of smaller shapes are taken from the map, and the contour pattern is increasingly generalized (smoothed out). For a number of landforms, non-scale symbols are used. This is how generalization occurs, i.e. image generalization relief.

Relief is the most important element of the terrain. The image of the relief on topographic maps gives a complete and fairly detailed idea of ​​the unevenness of the earth's surface, their shape and relative position, elevations and absolute heights of terrain points, the prevailing steepness and length of the slopes.

Relief on topographic maps is depicted as horizontal lines in combination with symbols of cliffs, rocks, ravines, gullies, stone rivers, firn fields, etc. The relief image is supplemented with elevation marks of characteristic points of the area, signatures of contour lines, relative heights (depths) and slope direction indicators (berg strokes). On all topographic maps, the relief is depicted in the Baltic height system, that is, in the system of calculating absolute heights from the average level of the Baltic Sea. Horizontal- this is a line on the map connecting relief points with that height above sea level. The following horizontal lines are distinguished:

• main (solid) - the relief section corresponding to the height;
• thickened - every fifth main horizontal line; stands out for ease of reading the relief;
• additional horizontals (semi-horizontals) - drawn by a broken line with the height of the relief section equal to half) of the main one;
• auxiliary - depicted by short, broken, thin lines at an arbitrary height.

The distance between two adjacent main horizontal lines in height is called relief section height. The height of the relief section is indicated on each sheet of the map under its scale. For example, “Solid horizontal lines are drawn every 10 meters.”

On topographic maps, the main section heights (in meters) are accepted according to Table 1.

Table 1. — Main section heights in meters.

The main heights of the relief section for maps of scales 1:500,000 and 1:1,000,000 are set in accordance with altitudinal zones on the following variable scale (Table 2).

Table 2. - Variable scale of altitude zones.

Additional horizontals (semi-horizontals) are used to display characteristic shapes and details of the relief (bends of slopes, peaks, saddles, etc.), if they are not expressed by the main horizontals. In addition, they are used to depict flat areas when the gaps between the main contour lines are very large (more than 3-4 cm on the map).

Auxiliary horizontal lines are used to depict individual relief details (saucers in steppe regions, depressions, individual hillocks on flat terrain), which are not conveyed by the main or additional horizontal lines.

For additional characteristics of the relief, height marks of characteristic points of the area are signed on maps: the tops of mountains and hills, the highest points of watersheds, passes, saddles, the lowest points of the bottom of valleys, as well as points that are landmarks (at intersections of roads and clearings, at sharp bends of the contours of vegetation). cover, etc.). Elevation marks of the most prominent points of the terrain (command points - having the greatest height and allowing a good view of the surrounding area from them) are highlighted in a larger font. Such marks are selected in the amount of 3-4 per sheet of the map.

Contour signatures are given in such quantity and are placed in combination with elevation marks of points so that you can easily and quickly determine the height of a particular point on any part of the map sheet.

In order to be able to read the shapes of the relief and clearly see in which direction the slope goes down, short lines are placed on the horizontal lines - ramp direction signs or berg strokes. They are always directed towards the downward direction of the slope.

To practically determine the steepness of the slopes, a plotting graph is placed on the map (to the right of the scale). It is given for two heights: one for the fills between the main ones, the other for the fills between the thickened horizontals. When determining the steepness of the slope using the laying graph (Figure 1), it is necessary to measure the segment between two adjacent main or thickened horizontal lines with a compass, ruler or strip of paper, attach it to the graph and read the number of degrees at the base (Figure 2).

Figure 1. — Determination of slope steepness: a — according to the laying schedule; b - according to the formula.

Figure 2. — Determining the steepness of slopes using a compass.