Lesson - 1 - Narajole Raj College

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Lesson - 1

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Proportional Circle Diagram

Definition:

Circles or wheel diagrams is a another type of 2-Dimensional diagram, where a series of circles proportional in size which represent to quantities. It is also called Proportional area chart.

Type:

Generally circle diagram are two types –

a. Simple Circle Diagrams: When each proportional circle represents a single value of only one component of data.

b. Compound Circle diagrams or Wheel diagrams or proportional pie diagrams or pie charts:

When the more than one component data comprises within a circle and also it respectively divided into angular segments to show its componential parts.

Principle of the Circle diagram:

 The area (A) of a circle for a accountable item (i) is directly proportionate to the quantity (Q) of the item to be represents. So, a circle of one unit area (A) represents a quantity (Q). Another word, item being proportionate in diameter in terms the amount of area or figure of item they represent, are often placed in thematic maps, more or less within the boundary of the respective administrative division.

Method:

The radius of such circles can be computed by considering the respective area as (Q) = 𝜋 𝑟² Or, 𝑟² = ^𝑄

𝜋

Or, Radius of a circle (r) = ^𝑄

𝜋………(i)

(Where, „r‟ is the radius of the circle, and „Q‟ usually represent the total quantity of the area)

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 “r” value of various circle will be converted into a Cm. or inches according to the scale chosen. scale are should be carefully selected that individual circles are not too large or too small for the respective base map or administrative division on which it will be placed. The circle will befit the size and should not cover the entire boundary of the respective administrative map.

 A proportional scale must be diagrammatically represented with at least three circles corresponding roughly to the largest, smallest, and median rounding off values of the distribution.

 In case of pie-diagram or divided circles is proportionately divided into angular segments to show its constituent parts. The angular value of proportion circle evaluated from the equation:

θ =

³⁶⁰^𝑂

𝑇𝑜𝑡𝑎𝑙 𝑞𝑢𝑎𝑛𝑡𝑖𝑡𝑦 𝑜𝑓 𝑐𝑜𝑚𝑝𝑜𝑛𝑒𝑛𝑡

× 𝑄𝑢𝑎𝑛𝑡𝑖𝑡𝑦 𝑜𝑓 𝑠𝑝𝑒𝑐𝑖𝑓𝑖𝑐 𝑐𝑜𝑚𝑝𝑜𝑛𝑒𝑛𝑡…………..(ii)

 The drawing of the angular segments for each circle must start from a fixed line and the respective order of drawing should be maintained throughout.

 The legend is well planned in colors or shades must be drawn for the divisions of the main item.

Proportional Circle / Pie Diagram

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Characteristics:

 The circumference of all circles will be 360^O, but the angular of the segment of the circle is heterogeneous.

 The homogeneous color or shade can be used inside each circle. But in the case of pie diagram, different shades or shading are used for each segment.

Advantages

 This diagram displays the relative proportions of multiple classes of data

 The size of the circle is represented in proportion to the total quantity.

 This diagram summarizes a large data set in visual form.

 This diagram is visually simpler than other types of graphs.

 This diagram allows a visual check of the rationality or accuracy of the calculation.

 This diagram requires a minimum of additional explanations.

 This diagram is easily understood due to its wide use in business and media.

Disadvantages

 This diagram do not easily reveal exact values.

 Many pie charts may be needed to show changes over time.

 This diagram fails to reveal key assumptions, causes, effects, or patterns.

 This image is to be easily manipulated to get yield a false impression.

Limitation:

 Proportional circle or Pie diagram should be placed in such a way that they do not touch the respective administrative boundaries. However, in some cases, if the unit is longer than the size of an administrative area on the map, then any part of the diagram may exceed the administrative boundary, which is acceptable.

Proportional Pie Diagram

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𝜋 = 𝐶𝑖𝑟𝑐𝑢𝑚𝑓𝑒𝑟𝑒𝑛𝑐𝑒 𝐷𝑖𝑎𝑚𝑒𝑡𝑒𝑟 (2𝑟)

Circumference = π × diameter

2r r

Area = 𝒓^𝟐

Circle Area = 𝝅 𝒓^𝟐

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Q. Prepare a simple proportional circles diagram to show the population of different C.D. blocks of the Jhargram Dist. (2011) according to the given data:

Sl.

No.

Name of C.D.

Blocks

Total population

1 Jhargram 231809

2 Binpur-I 156153

3 Binpur-II 164522

4 Jamboni 113197

5 Nayagram 142199

6 Sankrail 115418

7 Gopiballavpur-I 108254 8 opiballavpur-II 104996

Jhargram

Jhargram Binpur – I

Gopiballavpur - I Gopiballavpur - II

Sankrail

Nayagram Binpur - II

Jamboni

0 20

10

Km.

20

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Sl. No Name of C.D. Block Total population (P_T)

Radius of a Circle ( 𝐫 = ^𝑷^𝑻

𝝅 ) Units

Scale Selection

Radius of a circle according to scale (

1 cm. to 500 units) Cm.

1. Jhargram 231809 271.638

1cm. to 500 units

0.543

2. Binpur-I 156153 222.946 0.446

3. Binpur-II 164522 228.843 0.458

4. Jamboni 113197 189.820 0.380

5. Nayagram 142199 212.752 0.426

6. Sankrail 115418 191.673 0.383

7. Gopiballavpur-I 108254 185.630 0.371

8. Gopiballavpur-II 104996 182.815 0.366

For proportional or Graphical Scale

1 (Largest) 250000 282.095 0.564

2 (Median) 175000 236.017 0.472

3 (Smallest) 100000 178.412 0.357

Step – 1: Calculation table for Proportional circle Diagram of the population of different

CD block of the Jhargram district:

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Step 2: Calculate the radius of a circle

Formula:

Radius of a circle (r) =

^𝑄

𝜋

( Where, “Q” represent the total quantity of the area)

For example of Jhargram CD Block Radius of a circle of (r) =

^𝑃^𝑇

𝜋

(Where, “P

_T^”

represent the total population of the respective area)

Or, r =

231809

𝜋 = 271.6378 Units

So, radius of a circle of Jhargram CD block is 271.6378 units

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Step 3: Calculate the radius of a circle according to selected scale.

Radius of a circle according to scale = Actual radius of a circle (

𝑟)

Selected Scale

(1 𝐶𝑚.𝑡𝑜 500 𝑈𝑛𝑖𝑡)

For example of Jhargram CD Block

Radius of a circle according to scale

= 271.6378

500

Cm = 0.543 Cm.

Step 4: Diagram

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Jhargram

Step – 1 (Reading have been taken from the last column of the calculation sheet)

Step - 2 Step - 3

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PROPORTIONAL SCALE Population (Persons)

250 175 100 Step- 1: Diameter (2r) of the

largest proportional circle

Step – 2: Radius of the median proportional circle

Step – 3: Draw the median Circle

Step – 4: Radius of the smallest circle Step - A

Step - B Step - C

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Showing the population of different C.D. block of Jhargram district (2011)

LEGEND

PROPORTIONAL SCALE

10 20

Km.

20

Jhargram Binpur – I

Gopiballavpur - I Gopiballavpur - II

Sankrail

Nayagram Binpur - II

Jamboni

Population (000, Persons)

250 175 100

Total Population

0

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Drawing Procedure On Worksheet With Out Respective Map

Jhargram Binpur – I

Gopiballavpur - I Gopiballavpur - II

Sankrail Nayagram

Binpur - II Jamboni

LEGEND

PROPORTIONAL SCALE Population (000, Persons)

Total Population

175 100 250

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Interpretation

Proportional circle in the map of the Jhargram district depict the total population of

different CD blocks. From the map, it can be interpreted that the distribution of total

population in each CD block of Jhargram District is quite uneven. Jhargram, Binpur-II,

Nayagram, and Binpur-I, etc. CD blocks are carrying huge population pressure. On the

other hand Gopiballavpur-II, Gopiballavpur-I, Jamboni, and Sankrail etc. CD blocks have

less population pressure than other CD blocks. The reason for such a situation is that in all

the blocks where there are more job opportunities as well as the suitability of the living

land, the population is higher in those blocks, and in some blocks the adverse conditions

reduce the population.

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1 .Chandrakona I 2. Chandrakona II 3. Dantan I 4. Dantan II 5. Daspur I 6. Daspur II 7. Debra 8. Garbeta I 9. Garbeta II 10. Garbeta III 11. Ghatal 12. Keshiary 13. Keshpur 14. Kharagpur I 15. Kharagpur II 16. Midnapore 17. Mohanpur 18. Narayangarh 19. Pingla 20. Sabang 21. Salbani

2 1

3 4

6 5 7 8

9

10

11

12

13

14 15 16

17 18

19 20 21

Paschim Medinipur

Km.

Q. Prepare a proportional circles diagram to show separately - area, population, and household of different C.D. blocks of the Paschim Medinipur district (2011) according to the given data:

Sl No.

Tehsil (CD Block)

Area (km²) Population (2011)

No. of Household

3 Chandrakona I 196 1,72,001 30369

4 Chandrakona II 171 1,46,898 26263

5 Dantan I 257 1,72,107 38259

6 Dantan II 187 1,55,017 32809

7 Daspur I 171 2,03,987 44090

8 Daspur II 162 2,38,529 50053

9 Debra 368 2,88,619 66456

10 Garbeta I 421 2,28,513 46452

11 Garbeta II 353 1,48,410 30680

12 Garbeta III 304 1,69,528 34484

13 Ghatal 216 2,86,264 56385

18 Keshiary 293 1,49,260 35298

19 Keshpur 499 3,39,248 68756

20 Kharagpur I 229 4,65,644 58335

21 Kharagpur II 256 1,83,440 44637

22 Midnapore 327 3,60,969 42326

23 Mohanpur 133 1,11,901 24107

24 Narayangarh 510 3,02,620 68886

26 Pingla 244 1,94,809 46904

27 Sabang 296 2,70,492 63167

28 Salbani 554 1,88,653 39334

Data Source link: https://censusindia.gov.in/2011census/dchb/DCHB_A/19/1918_PART_A_DCHB_PASCHIM%20MEDINIPUR.pdf

Key

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To be continue Lesson - 2

Reference:

1. Misra, R.P., Ramesh,A., 2002, Fundamentals of Cartography, Revised and Enlarged, pp. 542-458

2. Monkhouse, F.J., Wilkinson, H.R.,1976, Maps and Diagrams, Methuen & Co LTD, London, pp. 288-305 3. Sarkar, A., 2009, Practical Geography, revised edition, orient black swan, Kolkata, pp.163-169.

4. Sing, R.L., Sing, R.P.B., 2014, Elements of Practical Geography, Kalyani Publishers, New Delhi, pp. 162-190.