Scale B.A B.Sc Practical HS Geography practical GEOGRAPHY PRACTICAL GRADUATION :- SCALE উচ্চমাধ্যমিক ভূগোল প্র্যাক্টিক্যাল স্কেল ucchomadhymick practial Scale

              SCALE

Written by  Firoz Mallick

DEFINITION :- The scale is the measure for proportional and true representation of the reduced earth on a paper. The scale expresses the relationship between the size of object on the ground and its image on the map. In terms of measurement made on one to be related in terms of the others. The technically a map scale is the relationship between the distance measured on the map and the corresponding distance on the ground. Actually a map is a model of the real world.

 CLASSIFICATION OF SCALE

 Scale is mainly 3 types:-
1. STATEMENT SCALE.
2. GRAPHICAL SCALE.
3. NUMERIC RATIO SCALE.

2.Graphical scale is also 4 types :- 
(a) Vernier Scale.
(b) Linear Scale.
(c) Comparative Scale.
(d) Diagonal Scale.

(a). Vernier Scale is also 2 types :-
(i) Simple Vernier Scale.
(ii) Double Vernier Scale.

(i). SIMPLE VERNIER SCALE :- Simple Vernier Scale is also 2 types:-

1. Direct Vernier Scale.
2. Retrograde.

* DOUBLE VERNIER  SCALE :- Double Vernier Scale is 2 types :- 

1. Direct Vernier Scale.
2. Retrograde.

C. COMPARATIVE SCALE: Comparative Scale is also 4 types :-

(A). Unit Scale.
(B). Time Scale.
(C). Pace Scale.
(D). Revolution Scale.

*GRAPHICAL SCALE*

A map also be cartographical represented by a line or linear graph. This is known as a Graphical Scale.

• CHARACTERISTIC :-

1. The straight line is devided into a number of equal parts primary, secondary or tertiary division and the actual ground distance for the divisions are indicate there.
2. Graphical scale can be constructed from either a statement scale or a numeric ratio scale.

•MERITS:- 

1. It can be convincingly used by a layman.
2. A reproduction of the original map by reduction can be possible.

*LINEAR SCALE*
This is the simplest scale from of a Graphical scale shown as a linear scale.

*COMPARATIVE SCALE*
It is defined as a composite plain scale in which to linear scale representing different unit of measurement. Comparative scale are of four types a unit scale :- 
(a). UNIT SCALE.
(b). TIME SCALE.
(c). PACE SCALE.
(d). REVOLUTION SCALE.

(a). UNIT SCALE :- This type of comparative scale shows a comparison of distance measure of different but comparative unit.
Example:- km/mile.

(b). TIME SCALE :- This scale represents a relationship between time and distance.

(c). PACE SCALE :- It is a type of time scale specially used by the army. The length of a standard military base in 30 inch or 75 cm.

(d). REVOLUTION SCALE :- On a level ground distance can be measure in terms of the revolution of the wheel a vehicles.

*STATEMENT SCALE*
A map scale may be in the from of simple statement in which the map distance is always expressed as a unit length, this is known as a statement scale.

•EXAMPLE:- 1 cm represent to 25 km, 1 inch represent to 50 mile etc.

• CHARACTERISTIC :- The value of the hand side at the statement,indicates the map distance and that on the right hand side indicates the ground distance (km/mile).

• DEMERITS :- 
1. A layman,it aren't the various scale of measurements will not be able to read the map.
2. The reproduction of the original mapping reduction or enlargement is not possible and necessitates a determination of a new scale.

*NUMERIC RATIO SCALE*
A map scale may also be expressed as a numerical ratio,in which the numerator the map distance and the denominator is the corresponding ground distance. Both be expressed in the same unit of measurement. It is a dimensionless fraction. It is also known as a ratio or representative fraction.

• EXAMPLE :- 1:50000.

• DEMERITS :- Reproduction of the original map by reduction or enlargement is not possible and necessitates a determination of a new scale.

*DIAGONAL SCALE*
It is a type of graphical scale contains three types of divisions primary, secondary and tertiary. On large scale or code steal map are often design 1/100 the part of primary division and they are lies the importance and used of a diagonal scale.

*VERNIER SCALE*
The vernier scale is device formulated by B.P Vernier by which ever the fractional part of the smallest division of a main scale can be measure with the highest precision. It consist of a small auxiliary scale called the vernier scale which moves freely with its graduated edge along of fixed scale called the main scale.

•CHARACTERISTIC:- 
1. The scale can be drawn as a straight linear graph.
2.The vernier carries an index mark that famous the vernier division and its donated by arrow mark.
3.It is graphically used on the instrument like Theodolite.