Mtl is equal to what. Dynamic heads and microphones

visually the distance is determined by comparison with a segment known on the ground. The accuracy of the visual determination of the distance is influenced by the illumination, the size of the object, its contrast with the surrounding background, the transparency of the atmosphere, and other factors. Distances appear smaller than they actually are when viewed through bodies of water, hollows and valleys, when observing large and separately located objects. Conversely, the distances seem larger than in reality when viewed at dusk, against the light, in fog, in cloudy and rainy weather. All these features should be taken into account when determining distances by eye. The accuracy of the eye measurement of distances also depends on the training of the observer. An experienced observer can determine distances up to 1000 m by eye with an error of 10-15%. When determining a distance of more than 1000 m, errors can reach 30%, and with insufficient experience of the observer, 50%.

Determination of distances by speedometer. The distance traveled by the car is determined as the difference between the speedometer readings at the beginning and end of the journey. When driving on paved roads, it will be 3-5% more, and on viscous soil 8-12% more than the actual distance. Such errors in determining distances on the speedometer arise from wheel slip (track slip), tire tread wear and changes in tire pressure. If it is necessary to determine the distance traveled by the machine as accurately as possible, it is necessary to amend the speedometer readings. Such a need arises, for example, when moving in azimuth or when orienting using navigational instruments.

The amount of the correction is determined before the march. For this, a section of the road is selected, which, by the nature of the relief and soil cover similar to the route ahead. This section is passed at marching speed in a straight line and reverse directions, taking readings of the speedometer at the beginning and end of the section. According to the data obtained, the average value of the length of the control section is determined and the value of the same section, determined on the map or on the ground with a tape (tape measure), is subtracted from it. By dividing the result obtained by the length of the section measured on the map (on the ground), and multiplying by 100, a correction factor is obtained.

For example, if the average value of the control section is 4.2 km, and the measured value on the map is 3.8 km, then the correction factor

K \u003d ((4.2-3.8) / 3.8) * 100 \u003d 10%

Thus, if the length of the route measured on the map is 50 km, then the speedometer will read 55 km, i.e. 10% more. The difference of 5 km is the amount of the correction. In some cases, it may be negative.

Measuring distances in steps. This method is usually used when moving in azimuth, drawing up terrain diagrams, drawing individual objects and landmarks on a map (scheme), and in other cases. Steps are usually counted in pairs. When measuring a long distance, it is more convenient to count the steps in triplets alternately under the left and right foot. After every hundred pairs or triplets of steps, a mark is made in some way and the countdown starts again. When converting the measured distance in steps to meters, the number of pairs or triples of steps is multiplied by the length of one pair or triple of steps. For example, there are 254 pairs of steps between the turning points on the route. The length of one pair of steps is 1.6 m. Then D \u003d 254X1.6 \u003d 406.4 m.

Usually the step of a person of average height is 0.7-0.8 m. The length of your step can be determined quite accurately by the formula

D \u003d (P / 4) + 0.37,

where D is the length of one step in meters

R is the person's height in meters.

For example, if a person's height is 1.72 m, then the length of his step

D \u003d (1.72 / 4) + 0.37 \u003d 0.8 m.

More precisely, the step length is determined by measuring some flat linear section of the terrain, such as a road, with a length of 200-300 m, which is measured in advance with a measuring tape (tape measure, range finder, etc.). With an approximate measurement of distances, the length of a pair of steps is taken equal to 1.5 m.

Average error measuring distances in steps, depending on traffic conditions, is about 2-5% of the distance traveled.

Steps can be counted using a pedometer (Fig. 1). It has the look and feel of a pocket watch. A heavy hammer is placed inside the device, which, when shaken, falls, and under the influence of a spring returns to its original position. In this case, the spring jumps over the teeth of the wheel, the rotation of which is transmitted to the arrows. On the large scale of the dial, the arrow shows the number of units and tens of steps, on the right small one, hundreds, and on the left small one, thousands. The pedometer is suspended vertically from the clothes. When walking, due to oscillation, its mechanism comes into action and counts each step.

Fig.1 Pedometer

Determination of distance by time and speed of movement. This method is used to approximate the distance traveled, for which the average speed is multiplied by the time of movement. average speed pedestrian about 5, and when skiing 8-10 km / h. For example, if the reconnaissance patrol moved on skis for 3 hours, then it traveled about 30 km.

Determination of distances by the ratio of the speeds of sound and light. Sound propagates in the air at a speed of 330 m / s, i.e. rounded 1 km in 3 s, and light is almost instantaneous (300,000 km / h). Thus, the distance in kilometers to the place of the flash of a shot (explosion) is equal to the number of seconds elapsed from the moment of the flash to the moment when the sound of the shot (explosion) was heard, divided by 3. For example, the observer heard the sound of an explosion 11 seconds after the flash. Flash distance

D = 11/3 = 3.7 km.

Determination of distances by ear. A trained ear is a good helper in determining distances at night. The success of this method largely depends on the choice of listening location. It is chosen in such a way that the wind does not fall directly into the ears. Around within a radius of several meters, the causes of noise are eliminated, for example, dry grass, bush branches, etc. On a calm night with normal hearing, various sources of noise can be heard at the distances indicated in Table. one.

Table 1

Determination of distances by geometric constructions on the ground. This method can be used to determine the width of difficult or impassable terrain and obstacles (rivers, lakes, flooded areas, etc.). Figure 2 shows the determination of the width of the river by building on the ground isosceles triangle. Since in such a triangle the legs are equal, the width of the river AB is equal to the length of the leg AC. Point A is chosen on the ground so that a local object (point B) on the opposite bank can be seen from it, and a distance equal to its width can be measured along the river bank. The position of point C is found by the approximation method, measuring the angle DIA with a compass until its value becomes equal to 45 °.

Fig.2 Determination of distances by geometric constructions on the ground.

Another version of this method is shown in Fig. 23.6. Point C is chosen so that the angle ACB is 60°. It is known that the tangent of an angle of 60° is equal to 1/2, therefore, the width of the river is equal to twice the value of the AC distance. Both in the first and in the second case, the angle at point A must be equal to 90 °.

Determination of distances by angular dimensions objects is based on the relationship between angular and linear quantities. The angular dimensions of objects are measured in thousandths using binoculars, observation and aiming devices. The distance to objects in meters is determined by the formula

D \u003d (B / Y) * 1000,

where B is the height (width) of the object in meters;

y is the angular magnitude of the object in thousandths. For example (see Fig. 17), the angular size of a landmark observed through binoculars (an individual tree), whose height is 12 m, is equal to three small divisions of the binocular grid (0-15). Therefore, the distance to the landmark

D \u003d (12/15) * 1000 \u003d 800 m.

Determination of distances by linear dimensions of objects is as follows. Using a ruler located at a distance of 50 cm from the eye, measure the height (width) of the observed object in millimeters. Then the actual height (width) of the object in centimeters is divided by the measured ruler in millimeters, the result is multiplied by constant number 5 and get the desired height of the object in meters.

D \u003d (Forward / Vlin.) * 5

For example, a telegraph pole 6 m high (Fig. 1) closes a segment of 10 mm on the ruler. Therefore, the distance to it

D \u003d (600/10) * 5 \u003d 300 m.

Fig.1 Measuring the distance to the pole according to the linear dimensions of the object.

The accuracy of determining distances by angular and linear quantities is 5-10% of the length of the measured distance. To determine the distances by the angular and linear dimensions of objects, it is recommended to remember the values \u200b\u200b(width, height, length) of some of them, given in Table. one.

When you are in an unfamiliar area, especially if the map is not detailed enough with a conditional reference of coordinates or with no such reference at all, it becomes necessary to focus on the eye, determining the distance to the target different ways. For experienced travelers and hunters, determining distances is carried out not only with the help of many years of practice and skills, but also with a special tool - a rangefinder. Using this equipment, the hunter can accurately determine the distance to the animal in order to kill it with one shot. The distance is measured by a laser beam, the device is powered by rechargeable batteries. By using this device in hunting or other circumstances, the ability to determine the distance by eye is gradually developed, since when using it, the real value and the reading of the laser rangefinder are always compared. Next, methods for determining distances without the use of special equipment will be described.

Determination of distances on the ground is carried out in a variety of ways. Some of them belong to the category of sniper methods or military intelligence. In particular, during orientation on the ground, the following may be useful to an ordinary tourist:

Measuring in steps

This method is often used to map the area. As a rule, steps are considered in pairs. A mark is made after each pair or triple of steps, after which the distance in meters is calculated. To do this, the number of pairs or triples of steps is multiplied by the length of one pair or triple.

Angle measurement method.

All objects are visible at certain angles. Knowing this angle, you can measure the distance between the object and the observer. Considering that 1 cm from a distance of 57 cm is visible at an angle of 1 degree, it is possible to take the nail of the thumb of the outstretched hand equal to 1 cm (1 degree) as the standard for measuring this angle. The entire index finger is a reference of 10 degrees. Other standards are summarized in a table that will help you navigate the measurement. Knowing the angle, you can determine the length of the object: if it is covered with a thumbnail, then it is at an angle of 1 degree. Therefore, from the observer to the object is approximately 60 m.

By a flash of light

The difference between a flash of light and a sound is determined by a stopwatch. Based on this, the distance is calculated. As a rule, in this way, it is calculated by finding a firearm.

By speedometer
Time travel speed
By match

Divisions equal to 1 mm are applied to the match. Holding it in your hand, you need to pull it forward, hold it horizontally, while closing one eye, then combine its one end with top defined subject. After that, you need to advance the thumbnail to the base of the object and calculate the distance according to the formula: the distance to the object, equal to its height, divided by the distance from the observer's eyes to the match, equal to the marked number of divisions on the match.

The way to determine the distance on the ground using the thumb helps to calculate the location of both a moving and a stationary object. To calculate, you need to stretch your hand forward, raise thumb up. It is necessary to close one eye, while if the target moves from left to right, the left eye closes and vice versa. At the moment when the target is closed with a finger, you need to close the other eye, opening the one that was closed. In this case, the object will be pushed back. Now you need to make a count of the time (or steps, if the observation is for a person), until the moment when the object is again closed with a finger. The distance to the target is calculated simply: the amount of time (or pedestrian steps) before closing the finger a second time, multiplied by 10. The resulting value is converted to meters.

The distance recognition method by eye is the simplest, but requires practice. This is the most common method, since it does not require the use of any devices. There are several ways to visually determine the distance to the target: by segments of the terrain, the degree of visibility of the object, as well as its approximate value, which seems to the eye. To train the eye, you need to practice comparing the apparent distance to the target with a cross-check on the map or steps (you can use a pedometer for this). With this method, it is important to fix in memory some standards of measure of distance (50,100,200,300 meters), which are then mentally set aside on the ground, and evaluate the approximate distance by comparing the real value and the reference one. Fixing in memory specific segments of the distance also requires practice: for this you need to remember the usual distance from one object to another. In this case, it should be taken into account that the value of the segment decreases with increasing distance to it.

The degree of visibility and distinguishability of objects affects the setting of the distance to them with the naked eye. There is a table of limiting distances, based on which, you can imagine the approximate distance to an object that can be seen by a person with normal visual acuity. This method is designed for an approximate, individual finding of the ranges of objects. So, if, in accordance with the table, the facial features of a person become distinguishable from a hundred meters, this means that in reality the distance to him is not exactly 100 m, but no more. For a person with low visual acuity, it is necessary to make individual corrections regarding the reference table.

When establishing the distance to an object using an eye gauge, the following features should be taken into account:

Brightly lit objects, as well as objects marked bright color, appear closer to the true distance. This must be taken into account if you notice a bonfire, fire or distress signal. The same applies to large objects. Small ones seem smaller.
At dusk, on the contrary, all objects appear farther away. A similar situation develops during fog.
After rain, in the absence of dust, the target always seems closer than it actually is.
If the sun is in front of the observer, desired goal will seem closer than it really is. If it is located behind, the distance to the desired target is greater.
A target located on a level bank will always appear closer than one on a hilly one. This is due to the fact that uneven terrain hides the distance.
When viewed from high point downwards, objects will appear closer than when viewed from the bottom up.
Objects located on a dark background always appear further than on a light background.
The distance to the object appears less if there are very few observed targets in the field of view.

It should be remembered that the greater the distance to the target being determined, the more likely the error in the calculations. In addition, the more the eye is trained, the higher the accuracy of calculations can be achieved.

sound orientation

In cases where determining the distance to the target with an eye is impossible, for example, in conditions of poor visibility, rugged terrain or at night, you can navigate by sounds. This ability must also be trained. Identification of the target range by sounds is due to various weather conditions:

The clear sound of human speech is heard from afar in a quiet summer night, if the space is open. Audibility can reach 500m.
Speech, steps, various sounds are clearly audible on a frosty winter or autumn night, as well as foggy weather. AT last case it is difficult to determine the direction of an object because the sound is distinct but diffuse.
In a calm forest and over calm water, sounds travel very quickly, and the rain muffles them greatly.
Dry ground transmits sounds better than air, especially at night.

To determine the location of the target, there is a table of correspondence between the range of audibility and the nature of the sound. If you apply it, you can focus on the most common objects in each area (shouts, steps, vehicle sounds, shots, conversations, etc.).

It is often necessary to determine distances to various items on the ground. Distances are most accurately and quickly determined by means of special instruments (rangefinders) and rangefinder scales of binoculars, stereotubes, and sights. But due to the lack of instruments, distances are often determined using improvised means and by eye.

Among the common methods for determining the range (distances) to objects on the ground are the following: by the angular dimensions of the object; according to the linear dimensions of objects; visual; by visibility (distinctness) of objects; by sound etc.

Rice. 8. Determination of distances by the angular dimensions of the object (object)

Determination of distances by angular dimensions objects (Fig. 8) is based on the relationship between angular and linear values. The angular dimensions of objects are measured in thousandths using binoculars, observation and aiming devices, rulers, etc.

Some angular values (in thousandths of a distance) are given in Table 2.

table 2

The distance to objects in meters is determined by the formula: , where B is the height (width) of the object in meters; Y is the angular magnitude of the object in thousandths.

For example (see Figure 8):

Determination of distances by linear dimensions of objects is as follows (Fig. 9). Using a ruler located at a distance of 50 cm from the eye, measure the height (width) of the observed object in millimeters. Then the actual height (width) of the object in centimeters is divided by the measured ruler in millimeters, the result is multiplied by a constant number 5 and the desired height of the object is obtained in meters:

Rice. 9. Determination of distances by the linear dimensions of an object (object)

For example, the distance between telegraph poles equal to 50 m (Fig. 8) is closed on the ruler with a segment of 10 mm. Therefore, the distance to telegraph line equals:

The accuracy of determining distances by angular and linear values is 5-10% of the length of the measured distance. To determine the distances by the angular and linear dimensions of objects, it is recommended to remember the values \u200b\u200b(width, height, length) of some of them, given in Table. 3.

Table 3

Thing	Dimensions, m
Thing	Height	Length	Width
medium tank	2-2,5	6-7	3-3 5
armored personnel carrier	2	5-6	2-2,4
Sidecar motorcycle	1	2	1,2
Truck	2-2,5	5-6	2-3,5
A car	1,6	4	1,5
Four-axle passenger car	4	20	3
Four-axle railway tank car	3	9	2,8
Communication line wooden pole	5-7	—	—
Medium height man	1,7	—	—

Determination of distances by eye

Ocular is the simplest and fast way. The main thing in it is the training of visual memory and the ability to mentally set aside a well-represented constant measure (50, 100, 200, 500 meters) on the ground. Having fixed these standards in memory, it is easy to compare with them and estimate distances on the ground.

When measuring distance by successively mentally postponing a well-studied constant measure, it must be remembered that the terrain and local objects seem to be reduced in accordance with their removal, that is, if they are twice as far away, the object will appear twice as small. Therefore, when measuring distances, mentally set aside segments (measures of the terrain) will decrease in accordance with the distance.

In doing so, the following must be taken into account:

how closer distance, the clearer and sharper the visible object seems to us;
the closer the object, the larger it seems;
larger objects appear closer to smaller objects at the same distance;
a brighter-colored object appears closer than a dark-colored object;
brightly lit objects appear closer than dimly lit objects at the same distance;
during fog, rain, at dusk, cloudy days, when the air is saturated with dust, the observed objects seem further than on clear and sunny days;
the sharper the difference in the color of the object and the background on which it is visible, the more reduced the distances seem; so, for example, in winter, a snowy field, as it were, brings the darker objects located on it closer;
objects on flat terrain seem closer than on hilly ones, distances defined through vast expanses of water seem to be especially shortened;
terrain folds (river valleys, depressions, ravines), invisible or not fully visible to the observer, hide the distance;
when observing lying down, objects appear closer than when observing standing;
when viewed from the bottom up - from the foot of the mountain to the top, objects seem closer, and when viewed from the top down - farther;
when the sun is behind the soldier, the distance is hidden; shines in the eyes - it seems larger than in reality;
the fewer objects in the area under consideration (when observing through a body of water, a flat meadow, steppe, arable land), the shorter the distances seem.

The accuracy of the eye gauge depends on the training of the soldier. For a distance of 1000 m, the usual error ranges from 10-20%.

Determination of distances by visibility (distinctness) of objects

With the naked eye, you can approximately determine the distance to targets (objects) by the degree of their visibility. A soldier with normal visual acuity can see and distinguish some objects from the following limiting distances indicated in table 4.

It must be borne in mind that the table indicates the limiting distances from which certain objects begin to be visible. For example, if a serviceman saw a chimney on the roof of a house, this means that the house is no more than 3 km away, and not exactly 3 km away. It is not recommended to use this table as a reference. Each soldier must individually clarify these data for himself.

Table 4

Objects and features	The distances from which they become visible (distinguishable)
Separate small house	5 km
Roof pipe	3 km
Airplane on the ground tank in place	1 2 km
Tree trunks, kilometer posts and communication line poles	1.0 km
The movement of the legs and arms of a running or walking person	700 m
Machine gun, mortar, anti-tank gun, wire fence stakes	500 m
Light machine gun, rifle, color and parts of clothing on a person, oval of his face	250 - 300 m
Roof tiles, tree leaves, staked wire	200 m
Buttons and buckles, details of a soldier's armament	100 m
Human facial features, hands, details of small arms	100 m

Sound orientation.

At night and in fog, when observation is limited or impossible at all (and on rough terrain and in the forest, both at night and during the day), hearing comes to the aid of vision.

Military personnel must learn to determine the nature of sounds (that is, what they mean), the distance to the sources of sounds and the direction from which they come. If different sounds are heard, the soldier must be able to distinguish them from one another. The development of this ability is achieved by prolonged training (in the same way a professional musician distinguishes the voices of instruments in an orchestra).

Almost all danger sounds are made by humans. Therefore, if a soldier hears even the faintest suspicious noise, he should freeze in place and listen. If the enemy starts to move first, thereby giving away his location, then he will be the first to be detected.

Into the quiet midsummer night even ordinary human voice in open space it can be heard far away, sometimes for half a kilometer. In frosty autumn or winter night all sorts of sounds and noises can be heard very far away. This applies to speech, and steps, and the clinking of dishes or weapons. In foggy weather, sounds can also be heard far away, but it is difficult to determine their direction. On the surface of calm water and in the forest, when there is no wind, sounds are carried over a very long distance. But the rain dampens the sounds. The wind blowing towards the soldier brings the sounds closer and away from him. It also carries the sound to the side, creating a distorted view of the location of its source. Mountains, forests, buildings, ravines, gorges and deep ravines change the direction of the sound, creating an echo. Generate echo and water spaces, contributing to its spread over long distances.

The sound changes when the sound source moves over soft, wet, or hard ground, along the street, along a country or field road, over pavement, or over leafy ground. It must be borne in mind that dry earth transmits sounds better than air. At night, sounds are especially well transmitted through the ground. Therefore, they often listen with their ear to the ground or to tree trunks. Average hearing range various sounds during the day on flat terrain, km (in summer), is given in Table 5.

Table 5

Sound character	Range audibility, m
The crack of a broken branch	Up to 80
Steps of a person walking on the road	40-100
Oar strike on the water	Up to 1000
The blow of an ax, the ringing of a cross-cut saw	300-400
Digging trenches with shovels in hard ground	500-1000
Quiet conversation	200-300
Shout	1000-1500
The clatter of metal pieces of equipment	Up to 300
Loading small arms	Up to 500
Tank engine running on site	Up to 1000
Movement of troops on foot:
- on a dirt road	Up to 300
- by highway	Up to 600
Vehicle movement:
- on a dirt road	Up to 500
- by highway	Up to 1000
Tank movement:
- on a dirt road	up to 1200
- by highway	3000-4000
Shot:
- from a rifle	2000-3000
- from a gun	5000 and more
Gun firing	Up to 15000

To listen to sounds lying down, you need to lie on your stomach and listen while lying down, trying to determine the direction of the sounds. This is easier to do by turning one ear in the direction from which the suspicious noise is coming. To improve audibility, it is recommended to attach bent palms, a bowler hat, a piece of pipe to the auricle.

To better listen to sounds, you can put your ear to a dry board laid on the ground, which acts as a sound collector, or to a dry log dug into the ground.

The amount of the correction is determined before the march. To do this, a section of the road is selected, which, by the nature of the relief and soil cover, is similar to the upcoming route. This section is passed at marching speed in forward and reverse directions, taking speedometer readings at the beginning and end of the section. According to the data obtained, the average value of the length of the control section is determined and the value of the same section, determined on the map or on the ground with a tape (tape measure), is subtracted from it. By dividing the result obtained by the length of the section measured on the map (on the ground), and multiplying by 100, a correction factor is obtained.

For example, if the average value of the control section is 4.2 km, and the measured value on the map is 3.8 km, then the correction factor is:

When converting the measured distance in steps to meters, the number of pairs or triples of steps is multiplied by the length of one pair or triple of steps.

For example, there are 254 pairs of steps between the turning points on the route. The length of one pair of steps is 1.6 m. Then:

Usually the step of a person of average height is 0.7-0.8 m. The length of your step can be determined quite accurately by the formula:

Where D is the length of one step in meters; R is the person's height in meters.

For example, if a person's height is 1.72 m, then the length of his step will be equal to:

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Since in such a triangle the legs are equal, the width of the river AB is equal to the length of the leg AC.

Point A is chosen on the ground so that a local object (point B) on the opposite bank can be seen from it, and a distance equal to its width can be measured along the river bank.

Fig.10. Determination of distances by geometric constructions on the ground. The position of point C is found by the approximation method, measuring the angle DIA with a compass until its value becomes equal to 45 °.

Another version of this method is shown in Fig. 10b.

Point C is chosen so that the angle ACB is 60°.

It is known that the tangent of an angle of 60° is equal to 1/2, therefore, the width of the river is equal to twice the value of the AC distance.
Both in the first and in the second case, the angle at point A must be equal to 90 °.

Light Orientation very handy for maintaining a direction or for determining the position of an object on the ground. Moving at night to a light source is most reliable. The distances at which light sources are detected with the naked eye at night are given in Table 6.

Table 6

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We remember: What are the ways to determine the distance between two objects?

Keywords:distance, stride length, range finder, terrain pattern.

1. Methods for measuring distances. The distance traveled on a hike or the distance between two distant objects should be measured with a tape measure or a meter for a long time. In this case, it is more convenient to measure the distance in steps. To do this, you need to know the average length of your step. Recall that to determine the average step length, it is necessary to measure a distance on the ground using a tape measure, for example, 50 m. Then walk this distance with a regular step, counting the number of steps. Suppose you walked a distance of 50 meters and took 70 steps. Therefore, your average stride length is approximately 71 cm (5,000 cm: 70 = 71 cm)

When measuring long distances, it is more convenient to count steps in pairs (for example, only under the left foot).

Less accurately, the distance can be determined by the time spent walking. So, if you walk 1 km in 15 minutes, then you will walk 4 km in 1 hour. You can determine the distance by eye.

Sometimes devices called rangefinders are used to measure distances. The rangefinder is easy to make by yourself (Fig. 16).

In order to determine the distance to an object using a rangefinder, it must be held at arm's length in front of the eyes and, moving to the right or left, ensure that the entire figure of a person is visible through the slot. In this case, the base of the object should be at the bottom of the slot. Below it will be a number corresponding to the distance from the observer to the object. The figure shows that the distance in this example is 80 m.

Fig.16. The simplest rangefinder (the drawing is made in full size). Redraw the drawing on a sheet of thick cardboard and cut out the shaded part.

2. Types of terrain images. To decide where to build new factories, residential buildings, build roads, to plan the placement of crops, pastures, you need to have an image of the area. A small area can be drawn or photographed (Fig. 17).

Rice. 17. Snapshot of the area.

But there are other images of the earth's surface, from which you can clearly see various objects (forests, rivers, villages, fields, etc.), find out their sizes and mutual arrangement. These are aerial photographs (Fig. 18) and terrain plans (Fig. 19).

Rice. 18. Aerial photograph of the area. What objects can you see on an aerial photograph of a site?

Rice. 19. Plan of the area. How is it different from an aerial photograph?

Aerial photographs are obtained by photographing the Earth's surface from aircraft.

1. How to determine the distance by walking time? 2. What is the simplest device that can be used to determine the distance? 3. What types of terrain images do you know?

& 7. Site plan

At school, when studying geography and in the future, you will refer to the map to find out where different geographical objects are located, what are their properties. To do this, let's first get acquainted with what a terrain plan is and geographic map how people depict the surface of the Earth on them. Knowing how to use the plan is very important. So, for example, in an unfamiliar city, having a plan, you can find the right street, theater, museum, monuments and other objects. Builders, using the plan of the area, decide where it is better to lay a new road, build settlements in newly developed areas.

We remember: What is azimuth? How to determine the azimuth on the ground? How to determine the distance by walking time?

Keywords: drawing, site plan, conventional signs.

1. Plan of the area. Site plans, like aerial photographs, depict the area from above. But there are differences between a photograph, a drawing, an aerial photograph, and a ground plan.

The drawing and photograph of the area differs from the plan in that the figure shows the side view of the area, and the plan shows the top view of the area.

In the photograph, all objects are depicted in their natural form, and on the plan they are depicted with the help of conventional signs.

The terrain can also be depicted using a drawing, in which the distances will be shown to scale.

Thus, p l a n n o s t- This is a drawing of a small area of the earth's surface, made to a certain scale and using conventional signs. Component plan - symbols and scale.

2. Conventional signs. Objects and objects on the terrain plan are depicted using conventional signs (Fig. 20).

Rice. 20. Conventional signs of the area plan. Are the symbols similar to the objects they represent?

Many conventional signs depict objects that occupy large areas on the ground. These are fields, forests, swamps, thickets of bushes. The boundary between them on the plans of the area is shown by small dots.

Small rivers and streams, roads, narrow streets are depicted by conventional signs in the form of lines. By their length, you can find out the length of the depicted river or road. When drawing conventional signs on a plan, certain rules must be followed.

Fig.21. Incorrect (A) and correct (B) depiction of symbols on the plan.

* Conventional signs were already on the ancient planes. These were figures of animals and people, drawings of houses and fortress walls. The signs of the plans were different. On modern plans, the symbols do not change.

The development of conventional signs is challenging task. Well-designed symbols help to better read the plan and map, and facilitate their drawing. Signs should be simple and clear.

1. What is called a terrain plan? 2. Find on the terrain plan (Fig. 19.) a meadow, a mixed forest, thickets of shrubs, ravines and other terrain objects.

3. Using fig. 21, determine what mistakes were made on the left plan in the image of conventional signs of meadows, swamps, cut down forest, a single tree.

Practical work.

Build a table in which you reflect the differences in the image of the area in a drawing, photograph, aerial photograph.

& 8. The scale of the plans of the area.

We remember: How are objects marked on the map? What is an azimuth?

Keywords: scale, numerical scale, named scale, linear scale, orientation according to the terrain plan.

1. Types of scales. Suppose you need to draw on paper the distance from your school to your home. You already know that the distance from school to your home is 910 m. It is impossible to show this distance on paper in actual size, so you need to draw it to scale. M a c h t a b o m they call a fraction, in which the numerator is one, and the denominator is a number indicating how many times the distance on the plan is less than on the terrain itself. We will agree that on paper we will depict all distances 10,000 times less than in reality, i.e. on a scale of 1:10,000 (one ten-thousandth). This fraction can also be written as 1/10,000. This means that 1 cm on paper will correspond to 10,000 cm (or 100 m) on the ground. Then the distance from school to your home will be 9 cm 1 mm.

This type of scale is called h i s l e n n m

By the numerical scale, they find out how many times all distances are reduced on the plan. How more number in the denominator of the fraction, the greater the decrease. Now you can draw on paper the distance from your home to school.

The same scale can be written with the words "1 centimeter - 100m". This scale is called and m e n o v a n n m. It is convenient in that according to the line measured on the plan, you can immediately find out the distance on the ground.

A linear scale is also placed on the plans.

Linear scaling is a straight line divided into equal parts (usually centimeters). When drawing a linear scale, zero is set, retreating 1 cm from the left end of the segment, and the first centimeter is divided into smaller parts (2 mm each) (Fig. 22).

Rice. 22. Designation of the scale on the local plan and on the map.

The linear scale is used to determine distances according to the plan using a measuring compass (see Fig. 23).

Rice. 23. The position of the measuring compass when measuring distances on the plan using a linear scale.

2. Determining the azimuth according to the terrain plan. On the plans, the direction to the north is often indicated by an arrow. If the arrow is not shown, then it is considered that the upper edge of the plan is northern, the lower one is southern, the right one is eastern and the left one is western. Suppose that you need to go from the ferry on the Golubaya River to the dam on the Malinovka River (Fig. 24)

Rice. 24. Determining the azimuth according to the plan using a protractor.

To do this, you should know in what azimuth you need to move from the ferry in order to come to the dam. This azimuth can be determined according to the plan using a protractor (Fig. 24). What is the azimuth? On the ground, you find this azimuth using a compass and follow this azimuth in the right direction.

1. What is the scale? 2. What types of scales are distinguished? 3. What does the denominator of the numerical scale show? 4. When is it more convenient to use a named scale?

Practical work.

Draw a distance of 300 m on the drawing on a scale: 1 cm - 100 m, 1 cm - 30 m. Which of the scales is larger?

Draw a distance of 500 m on the drawing. Choose the scale yourself.

Read the scales 1:20,000 and 1:300,000. How many times are the distances reduced in the first and second cases? Convert these numerical scales to named ones. Express them in linear terms.

* The student depicted in the drawing a distance of 1 km with a segment 10 cm long. Determine which scale he chose to complete the task

* The student drew a distance of 500 m on the drawing on a scale of 1 cm - 50 m. What is this distance on the drawing?

** A student from point A to point B walked along an azimuth of 360 degrees 100 m (conditionally reflect this distance in a notebook on a scale of 1:1000). From point B to point C, he traveled the same distance along the azimuth of 90 degrees. From point B, he traveled the same distance along an azimuth of 180 degrees. Draw the student's path in a notebook and determine how far and in what azimuth he has left to go to point A.

Connoisseur Contest . You have found a plan. The part of the sheet where the scale is located has not been preserved. How to determine the scope of this plan?

Distance measurement is one of the most basic tasks in geodesy. There are different distances as well a large number of instruments designed for this work. So let's consider this question in more detail.

Direct method for measuring distances

If it is required to determine the distance to an object in a straight line and the terrain is available for research, such a simple device for measuring distance as a steel tape measure is used.

Its length is from ten to twenty meters. A cord or wire can also be used, with white markings after two and red after ten meters. If it is necessary to measure curvilinear objects, an old and well-known two-meter wooden compasses (sazhens) or, as it is also called, “Kovylok”, is used. Sometimes it becomes necessary to make preliminary measurements of approximate accuracy. They do this by measuring the distance in steps (based on two steps equal to the growth of the person measuring minus 10 or 20 cm).

Measurement of distances on the ground remotely

If the measurement object is in the line-of-sight zone, but there is an insurmountable obstacle that makes direct access to the object impossible (for example, lakes, rivers, swamps, gorges, etc.), distance measurement is applied remotely visual method, a more precisely by methods because there are several varieties:

High precision measurements.
Low-precision or approximate measurements.

The former include measurements using special instruments, such as optical rangefinders, electromagnetic or radio rangefinders, light or laser rangefinders, and ultrasonic rangefinders. The second type of measurement includes such a method as geometric eye measurement. Here is the determination of the distance by the angular magnitude of objects, and the construction of equal right-angled triangles, and the method of direct resection in many other geometric ways. Consider some of the methods of high-precision and approximate measurements.

Optical Distance Meter

Such measurements of distances to the nearest millimeter are rarely needed in normal practice. After all, neither tourists nor military intelligence officers will carry large and heavy objects with them. They are mainly used in professional surveying and construction work. Often used in this case is a device for measuring distance, such as an optical rangefinder. It can be either with a constant or with a variable parallax angle and be a nozzle for a conventional theodolite.

Measurements are made on vertical and horizontal measuring rails, which have a special mounting level. such a rangefinder is quite high, and the error can reach 1:2000. The measurement range is small and is only from 20 to 200-300 meters.

Electromagnetic and laser rangefinders

An electromagnetic distance meter belongs to the so-called pulse-type devices, the accuracy of their measurement is considered average and can have an error from 1.2 to 2 meters. But on the other hand, these devices have a great advantage over their optical counterparts, as they are optimally suited for determining the distance between moving objects. Their distance units can be calculated in both meters and kilometers, so they are often used in aerial photography.

As for the laser rangefinder, it is designed to measure not very large distances, has high accuracy and is very compact. This is especially true for modern portable devices. These devices measure the distance to objects at a distance of 20-30 meters and up to 200 meters, with an error of no more than 2-2.5 mm over the entire length.

ultrasonic rangefinder

This is one of the simplest and most convenient devices. It is light and easy to operate, and belongs to devices that can measure area and angular coordinates separately. given point on the ground. Nevertheless, in addition to the obvious advantages, it also has disadvantages. Firstly, due to the short measuring range, the distance units of this device can only be calculated in centimeters and meters - from 0.3 to 20 meters. Also, the measurement accuracy may change slightly, since the speed of sound propagation directly depends on the density of the medium, and, as you know, it cannot be constant. However, this device is great for quick small measurements that do not require high accuracy.

Geometric eye methods for measuring distances

Above we talked about professional methods of measuring distances. And what to do when there is no special distance meter at hand? This is where geometry comes in. For example, if it is necessary to measure the width of a water barrier, then two equilateral right triangles can be built on its shore, as shown in the diagram.

AT this case the width of the river AF will be equal to DE-BF. Angles can be adjusted with a compass, a square piece of paper, and even with the help of identical crossed twigs. There shouldn't be any problems here.

You can also measure the distance to the target through the barrier, also using the geometric method of direct resection, by constructing right triangle with the apex at the target and dividing it into two scaled ones. There is a way to determine the width of an obstacle with a simple blade of grass or thread, or a way with an exposed thumb ...

It is worth considering this method in more detail, since it is the simplest. On the opposite side obstacles, a conspicuous object is selected (it is necessary to know its approximate height), one eye is closed and the raised thumb of the outstretched hand is pointed at the selected object. Then, without removing your finger, close open eye and open closed. The finger turns out to be shifted to the side in relation to the selected object. Based on the estimated height of the object, approximately how many meters the finger visually moved. This distance is multiplied by ten and the result is the approximate width of the barrier. In this case, the person himself acts as a stereophotogrammetric distance meter.

There are many geometric ways to measure distance. To talk about each in detail, it will take a lot of time. But they are all approximate and are only suitable for conditions where accurate measurement with instruments is impossible.