# Before working on the map to determine the scale of the map.

Scale - the ratio of the length of the line taken by map (plan) to the actual length of the same line on the ground

Globe - (lat.Globules-ball) cartographic image of the Earth to the surface of the globe, preserving the geometric similarity and geographic contours of the area ratio. On the globe are preserved constant scale, called the principal, so it is possible to make correct measurements between different parts of the Earth's surface.

The main scale is the degree of reduction of the overall size of the Earth to the globe, which is then projected onto a plane. The main scale is numerically equal to the ratio of length of any segment on the surface of the globe to the corresponding length on the surface of the Earth.

What does it mean larger and smaller scale?

Example:Scale 1:2 000 000 1 cm on the map to 2000 000sm on the earth's surface.

scale 1:1 000 000 ... it is larger

The value of the main scale is signed in the bottom of the neat line or plan versions:.

– Numerical-1: 1000000

– Linear - split line into equal parts with captions

– Named - labels-1 cm 20km.

1 INCH = 30 NM

Units of measurement scales:

- 1 cm to 20 km.

- 1 INCH = 30 NM

Translation SCALE maps

If necessary, measure the distances on these maps (various scales, from 1:20 to 1: 150 inch / MM) use a linear scale, or translation in cm / km. we can use this relationship:

approximately: Scale cm / km Scale = d / mm: 4 x 3

right: Scale cm / km = Scale d / mm: 2.54 x 1.852

Example: Дано Scale в 1 дюйме 20 ММ

approximately: Scale cm / km = 20 : 4 х 3 = 15

right: Scale cm / km = 20 : 2,54 х 1,852 = 14,58

For work:

Scale inch / mm 30, 50. ANSWER: 21.9 cm / km, 36.5 cm / km

The distance between two points on the map are measured with a ruler. By measuring the distance in centimeters, the result is multiplied by the value in the mind of the scale.

S = ℓ cm × M

For example, the map scale 1:500000 (in 1cm - 5km), the measured distance between two points is 7.5 cm Then, S = 7,5 × 5 = 37.5 km.

The measurement accuracy is approximately 0.5mm map scale. In the example above (with the scale of 1:500000) the accuracy of the measured distance ± 250m.

EXAMPLE:

Map scale 1: 500,000, a 1 cm - 5 km. The measured distance of 9.5 cm on the map, the distance on the earth's surface = 9.5 × 5 = 47.5 km.

Map M 1: 2 000 000, a 1cm - 20 km. The measured distance of 16.2 cm on the map, the distance on the earth's surface = 16.2 × 20 = 324 km.

By eye to determine the distance between points on the map is very important. To facilitate the visual determination of distances is useful to remember that 1° arc of the meridian corresponds to 111km. It is also recommended to measure the width of the solution and remember the thumb and index fingers and palm of the hand. Using these intervals, and knowing the scale of the map after the necessary training, you can quickly determine distances without the aid of a ruler.

It should be noted that a well-trained eye estimation also avoids blunder of instrumental measurements.

What is the distance between the TM in the direction of 180º, with the difference in latitude between 3º?

Determining the length of the arc of the meridian and parallel.

When measuring distances usually used linear or angular values arcs on the surface of the sphere.

For terrestrial sphere R = 6371,116 km, the length of arc of a great circle is equal to (the equator and the prime meridian)

S = 2 p R = 2 × 3,14 = 6371116 40030869m = 40030km

Then the length of the arc on the equator in the 1 ° = 111,196 km » 111,2 km

1 = 185326m » 1,853 km

1 "= 30.9 m

Method 1. Spar = R • Δ λ/57, 3 • cos φ

Method 2. For the equivalent sphere R = 6371,116 km:

- Seq = Δ λ • 111,2,

- Spar = Seq • cos φ

Identify direction

How to identify (read off) the direction desired course? Prior to that, have you heard: the movement to N, E, SW. In the navigation you need a more accurate determination of the direction.

Turnover around - the circle - 360º.

The azimuth circle. In air navigation direction is generally measured angle to the direction of the north meridian.

Given roadway angle is the angle made between the northern direction of the meridian taken as the reference point and the line of the given path. It is measured from the prime meridian northerly direction to the direction of the intended track in a clockwise direction from 0 to 360°.

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