﻿Foundations of orientation: work with a map and compass | The survival encyclopedia

# Foundations of orientation: work with a map and compass

When working with topographic maps have to measure the distance in a straight line on a winding, and to measure and calculate angles. You must first know the scale of the map. Scale is the ratio of the length of the line on the map to the length of the corresponding line in the area, expressed in the same measures of length. There are numerical and linear scale maps.

Numerical scale of the map is written as a fraction or ratio of two numbers. The numerator is one, and the denominator — the number that shows how many times the actual size on the ground reduced the depiction on the map. For example: 1:10 000. Number 10 of 000 indicates that all distances on the ground reduced to 10 000 times.

To work successfully with the card is a necessary knowledge of symbols, which are used most frequently (Fig. 24, 25).

To determine the map distances between local objects are the numerical scale. For this measure with a ruler or compass distance between local objects in centimeters and multiply that number by the amount of scale. For example, if the map scale of 1:25 000 the distance between two points is equal to 5.5 cm, the distance on the ground is equal to 5,5> <250f = 1375 m

To determine the short distance between two points is easier to use a linear scale. Linear scale — is a graphic representation of numerical magnitude. He is a straight line, divided into segments of equal length, called the base of a linear scale (Fig. 26). The base is chosen so that it corresponds to the area round the number of hundreds or thousands of miles away. If you need to construct a linear scale for the 1:50 000 maps, the better to take the base interval of 2 cm then each such segment corresponds to the area within 1 km. If you want to measure the line, which is less than the length of the base, the base is divided by 5-10 equal parts. As the line on the map can not be measured accurately, the distance on the ground 10 and 50 m, corresponding to 0.01 cm on the map, showing the subject within the map scale. Almost measurement error lines on the map in the field of 0.05 cm or more.

In the practice of tourism often do not use cards or photocopies of metric scale maps of any scale. To such a card, you could work, you need to build a transfer linear scale (Fig. 27). For example, make a photocopy of map scale 1:300 LLC. Scale photocopies obtained equal 1:387 865. If you build a linear scale with a base of 1 cm, then he will be in-kind match 3 878.65 m This creates difficulties in working with such a scale. More convenient to build a linear scale, the base of which in nature would be consistent with a round number of kilometers or hundreds of meters, for example, 5 m long LLC find a base in the following proportions: 1 cm: X cm = 3878.65 m: 5000 m X = 1.29.

Fig. 27 Conversion linear scale

Measuring distances in a broken line made with a compass or curvimeter. When using a compass to make a small target, depending on the degree of tortuosity of the measured distance. Odometer has the form of a box with a circular holder. In the center of the device is the dial with an arrow at the bottom of a wheel, with which encircled the route. The transmission system is connected to the wheel with the arrow on the dial, which counts the value of distance on the map.

Dividing the odometer on the scale of the dial are different: for some they represent the path the wheel on the map in centimeters on the other — are shown directly on the ground distance in kilometers, depending on the map scale. The figure (Fig. 28a) shows odometer with three scales of various scales (1:100 000, 1:50 000, 1:25 000). Mark on the scale show the distance on the ground in kilometers.

To determine the length of the route using curvimeter need needle is set to the zero position dial. Then the odometer should

stand upright wheel at the starting point of the route and with uniform pressure rolling it along the route so that the testimony of the arrow increases (Fig. 286). In the final destination at the right read off the scale dial. The route will be equal to a count of times the scale interval. If the odometer is testifying in centimeters, to obtain the corresponding distance on the ground it is necessary to multiply the scale reading on the value of the map scale.

Fig. 286. Measuring distances with curvimeter

Topographical orientation. Under the topographical orientation should be understood orienteering, ie, determination of the place of its location relative to the horizon surrounding the local objects and terrain. Orienteering starts with defining the horizon of the compass. Of the many systems in tourist compass practice the widest possible use Liquid Compass' Sport-3. " The advantage of this compass is extremely fast willingness to work and ease of maintenance. Compass' Sport-3 "is equipped with a magnifying glass for reading maps and washer-shagometrom that are on the base plate of the instrument. When using any compass, remember that in a freely suspended magnetic needle at its ends will be directed to the north and south. But it is approximately. The arrow is not in the direction of true (geographic) meridian, and the direction of the magnetic meridian (Fig. 29). The angle between the true and magnetic meridian is called the deflection (declination). It is for each country is different and can be east (with a +) or west (with a -). The value of its large areas of Europe and Asia is less than 5-7 °, except in areas of magnetic anomalies. So in most cases it can be assumed that the magnetic meridian is almost identical to the true, and the northern end of the arrow shows the direction approximately north. However, for more precise guidance, especially when driving on the azimuth, we must consider the value of the inducement, which is indicated on topographic maps.

Fig. 29. The transition from the true azimuth to a magnetic

To use a compass to determine the side of the horizon, it should release the brake of the magnetic needle compass and set horizontally. Then turn it up to the northern end of the arrow was against the letter "C" (North). In this situation, the letter "B", "3" and "U" will indicate the direction of the east, west and south. In any of these areas, you can select an object on the ground — the landmark, which will be used later to guide the drive on route.

At movement of the azimuth must carefully maintain the direction and often consult the compass. For a more accurate guide to the exit should not be given a very long distance between the turning points. In the case of obstacle avoidance on the opposite side of it should be noted a landmark and, beating, continue along the azimuth of this guide.

Horseback riding on the map. Having defined the compass side of the horizon, then you must correctly orient the map and find her point of their whereabouts. To do this, turn the map so that its top was sent to the selected item, and the card will be targeted.

Orienteering maps also can be produced by the compass and the two reference points. To do this, first set the compass diameter north-south on the vertical line of the grid to the north end of the north side of the frame and release the brake card magnetic needle. Then turn the card is supplied with the compass north end of the needle to the division corresponding to the correction direction: if the amendment is a positive direction (east), the arrow to the right to deviate from the vertical grid lines, if the amendment is a negative direction (west), the needle must be rejected left. Correction value is less than 3 ° can not be ignored, because the bug in the magnetic compass may be greater than the amendment.

Orienteering maps for two landmarks is the case. While on the ground at one point of reference, from which can be seen the other, searching for the map first landmark. Then turn the map so that the direction of the second landmark on the map coincides with the direction to him on the ground.

If the route is along a straight tourist area — roads, ditches, clearing, communication lines and power, the map is rotated so that the axis of the road (or other linear landmarks) on the map coincides with the axis of the road on the ground.

Definition of a point on the map distances. Once the map is oriented, we can solve a number of problems have arisen prior to the tourist areas. Most often, the tourist has to find a point of standing. This can be done in different ways and techniques. It's easier when this point is close to the local subject, shown on the map, symbol or image of the subject indicates the point standing.

If the point of standing on the ground and can not recognize it is far away from local objects, then turn to the simplest methods of topographic binding. Most often topographic techniques are binding the visual survey. Bind the visual topographic survey techniques can be performed when the local objects are removed from the point then bound by no more than 1 kilometer. First, choose the local objects, well recognizable on the map (marked on the map intersections of roads, rides, street crossings in populated areas, angles and power lines, ditches, churches, towers, water towers, individual monuments, burial mounds, individual trees, kilometer posts, bridges, and so on). Then orient the compass card or on a straight line path, if tethering point is on this circuit, and the sight of a Scribe endeavor with a ruler. Distance is measured in steps or by eye (if not more than 100 m). To go the distance, measured in meters, to the corresponding distances in meters, you need to know the scale of their steps. If not known, take 100 steps per usual 75-80 m

It is often used in tourist trips map, which is not specified geographic and magnetic meridian. And so tourists do not have to produce quite complex (especially for beginners) calculations. Suppose the group must pass the azimuth from the merger of streams to the clearing where the target of the route.

1) connect to map the source and target of the movement, that is, at the confluence of streams and point of reference;

2) Measure the magnetic azimuth protractor: the angle (clockwise) between the magnetic meridian and the direction of motion. Magnetic azimuth is 120 °. This figure is to be remembered, as the motion of the forest can lose sight, and then have to determine the azimuth again;

3) put the sight on the compass against the corresponding division of the limb;

4) open the catch and combine the north end of the compass needle at 0 ° on the limb;

5) determined using the viewfinder landmark, located in the direction of sight. Close the catch;

reaching a landmark, repeat 4-5-operations, etc.

Before going to always check the serviceability of the compass. With the lowered brake installed to the horizontal position. For any direction trays steel items, display her off balance and check whether it will return to its previous reading. If the arrow is not located in a constant position, so the compass is faulty, you can not use it.

It should be borne in mind that any compass may incorrectly indicate the side of the horizon. It happens during a thunderstorm near the power lines, the electric railways.

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