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What is the graphic scale?

It is represented by a graduated straight line, divided equally, in which the unit of measurement represents the length or distance in reality, and shows how many units in reality equals units of the drawing.

The graphic scale is the representation drawn on a Map, nautical chart one one plano with scale unit by unit, where each segment shows the relationship between the length of the representation and that of reality.1

It is represented by a graduated straight line, divided equally, in which the unit of measurement represents the length or distance in reality, and shows how many units in reality equals units of the drawing.

History of the graphic scale

The first representation of a graphic scale is found in the Carta pisana late 13th century, its shape consists of a circle on which one of its radios, that is divided into equal parts, each of these subdivisions corresponding to a scale distance that is not expressed numerically.

From 1318 the design has evolved with the replacement of the circle by a narrow bar, located on the banks of the maps, which can be horizontal or vertical, which is called leagues trunk, they continue to dispense with the numerical expression of the scale of representation that was necessarily implicit and that modern research has placed in units of 50 miles invariably for all portulan maps.

Graphic scale of a nautical chart. The biggest bar, represents a nautical mile (1,852 m), being 185 mm la 1/10 000 part of the distance represented.

Graphic scale of a world map, shows, graphically, scale change with latitude. Each unit on the map at the equator Represents earth at the same distance, how 5,9 units in latitude 80 °.

Graphic scales

DEFINITION: It is that scale in which the real dimensions of the object represented in the drawing are expressed in a graduated scale, that is to say, is the representation of the numerical scale.
The graphic scale allows us to directly know the dimensions of the real object, no need to perform mathematical operations

The counter scale represents the unit of the graphic scale divided by ten.

 

METRIC RELATIONS BETWEEN SCALES OF THE SAME SERIES:
In the scales a series is defined by the set of these that have in common the first number, varying only in tens, hundreds, thousands, etc., the series name is taken from the numerator and the first digit from the denominator (serie 1/2 understand the scales 1/2, 1/20, 1/200, 1/2000,…)
In the scales of the same series the marks remain, only varying the figures written below them (increasing or decreasing).
The subscale and its corresponding appreciation also varies depending on the scale used, although the number of divisions is the same - always 10 - the unit of measurement changes.

 

 

SCALIMETER READING:

The reading of measurements taken by means of the scale is not more difficult than those taken using a flying scale.
The scales that are attached to the scale, as well as the figures and their corresponding units of measurement facilitate the reading of any measurement to be taken in a drawing; you only have to take into account what was explained in the previous section regarding the appreciation of the different scales.
In the image below we have a scale that shows the scales 1:1 Y 1:10, it is easy to verify that the appreciation of each of them must be 1 mm y 1 cm respectively. So, the reading should be done considering the unit used in each one and its appreciation.

Graphic scales

It is possible to express the scales graphically and proportionally on a graduated segment. This procedure allows you to directly read and transport the measurements we need to understand or execute a drawing quickly and accurately..
The method with which a graphical scale is made (also known as a steering wheel) is based on determining the value of unity on that scale. So that this graphic scale also has an adequate working size, it is convenient to choose well the unit in which it will be developed. The tenths of a scale unit are measured by constructing the counter scale, for which said unit is divided into ten equal parts.
Example :
Suppose the scale is 1/8. We could also express it in decimal form: 0,125, which tells us that, for every unit in reality, we use 0,125 units in the drawing.
If we choose the centimeter as a unit, 100 actual cm would have a representation in the drawing of 12,5 cm; that is to say, 1 m would be equal to 12,5 cm. In this case, we will place on the edge of a paper or cardboard the measure of 12,5 cm and we will divide it into ten equal parts, with which we will obtain the value of each decimeter on the graphic scale.
Graphic scales
We show you some examples of forms of representation of different graphic scales.
Graphic scales

 

For the development of this topic, the recommendations of the UNE-EN ISO standard have been taken into account 5455:1996.


Concept

Representation of objects at their natural size is not possible when they are very large or when they are very small. In the first case, because they would require formats of unwieldy dimensions and in the second, because there would be a lack of clarity in their definition.

This problem is resolved by SCALE, applying the necessary enlargement or reduction in each case so that the objects are clearly represented in the drawing plane.

The SCALE as the relation between the dimension drawn with respect to its real dimension, this is:

Scale

If the numerator of this fraction is greater than the denominator, it is an enlargement scale, and it will be reduction otherwise. The scale 1:1 corresponds to an object drawn at its actual size (natural scale).

Standard scales

Though, in theory, it is possible to apply any scale value, in practice the use of certain standard values ​​is recommended in order to facilitate the reading of dimensions through the use of rulers or scalemeters.

These values ​​are:

scales-normalized

However, in special cases (particularly under construction) certain intermediate scales such as:

1:25, 1:30, 1:40, etc…

Practical examples

EXAMPLE 1

You want to represent in an A3 format the floor plan of a building 60 x 30 meters.

The most convenient scale for this case would be 1:200 which would provide dimensions of 30 x 15 cm, well suited to the size of the format.

EXAMPLE 2:

You want to represent in a A4 format a dimensional clock piece 2 x 1 mm.

The proper scale would be 10:1

EXAMPLE 3:

On a nautical chart to E 1:50000 a distance of 7,5 cm between two islets, What is the real distance between the two?

It is solved with a simple rule of three:

and 1 cm of the drawing are 50000 real cm
7,5 cm of the drawing will be real X cm

X = 7,5 x 50000 / 1 … And this results 375.000 cm, which are equivalent to 3,75 km.

Graphic scalegraphic scale

Based on Thales' Theorem, a simple graphical method is used to apply a scale.

see, for example, the case for E 3:5

  1. With origin at an arbitrary point O two lines r and s are drawn forming any angle.
  2. On the line r is the denominator of the scale (5 in this case) and on the line s the numerator (3 in this case). The ends of these segments are A and B.
  3. Any real dimension located on r will be converted into that of the drawing by a simple parallel to AB.

Universal triangle of scales

Through a triangle, we can build the simplest scales, both normalized and not. As we see in the figures, we can do it using an equilateral triangle of 10 cm sideways, or by means of an isosceles right triangle, whose legs measure 10 cm.


Universal-scale-triangle-01

Universal-scale-triangle-02

Transverse decimal scale

With this type of scale you can get, more accurately, the measurements of a scale segment, since in the so-called contra-scale, from the left side, we can appreciate the tenths and hundredths of unity.

In the following image we can see how we have constructed the decimal scale of transversal 1:20, and in it we have indicated two examples of measurements on it, 2,77 m y 1,53 m.

Scale-cross

Using the scaleescalimetro

In the usual practice of drawing, when working with scales, ladders are used.

The most common form of the scale is that of a 30 cm length, with starry section of 6 facets the guys. Each of these facets is graduated with different scales, which are usually:

1:100, 1:200, 1:250, 1:300, 1:400, 1:500

These scales are equally valid for values ​​that result from multiplying or dividing by 10, for example, the scale 1:300 is usable in scale drawings 1:30 from 1:3000, etc.

Another model, less usual of scale, is the fan scale, consisting of a series of rules on which the different graphic scales have been drawn.

Fan-scale

Examples of use:

  1. For a plane to E 1:250, scale will be applied directly 1:250 of the scale and the numerical indications that are read on it are the actual meters that the drawing represents.
  2. In the case of a plane to E 1:5000; scale will be applied 1:500 and we will have to multiply by 10 scale reading. For example, if a dimension of the plane has 27 units on the scale, we're actually measuring 270 m.

Of course, the scale 1:100 is also the scale 1:1, normally used as a ruler in cm.

references:
http://www.lanubeartistica.es/Dibujo_Tecnico_Primero/UD2/dt1_U2_tema_1_v01/33_escalas_grficas.html
https://www.google.es/search?sxsrf = ALeKk03frmbJAzzMCmLMpmKpwyqdy3tVBw% 3A1588058973570&= not XdunXo6tIpC0sAfE5ISoDw&q = scales + graphs&oq = scales + graphs&gs_lcp=CgZwc3ktYWIQAzICCAAyAggAMgQIABBDMgIIADICCAAyAggAMgIIADICCAAyAggAMgIIADoECAAQRzoECCMQJzoGCAAQFhAeOgcIIxDqAhAnOgUIABCDAToHCAAQgwEQQ1CsPFi0a2DtkwFoAXACeASAAbUBiAGgJ5IBBDAuMziYAQCgAQGqAQdnd3Mtd2l6sAEK&sclient = psy-ab&by = 0ahUKEwjOz4HYzIrpAhUQGuwKHUQyAfUQ4dUDCAw&uact=5
https://www.aulafacil.com/cursos/dibujo-lineal-secundaria/educacion-plastica-y-visual-3-eso/escalas-graficas-l9189
http://www.dibujotecnico.com/escalas-normalizadas/

D. ANGEL ALARCON MARTI

PRESIDENT / PROFESSOR Founder of the E.O.I.T International School of Survival.

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