NCERT Class 12 Geography Graphical Representation of Data

Graphichal Representation of Data

 You must have seen graphs, diagrams and maps showing different types of data.For example, the thematic maps shown in Chapter 1 of book for Class XI entitled Practical Work in Geography, Part-I (NCERT, 2006) depict relief and slope, climatic conditions, distribution of rocks and minerals, soils, population, industries, general land use and cropping pattern in the Nagpur district, Maharashtra. These maps have been drawn using large volume of related data collected, compiled and processed.

Have you ever thought what would have happened if the same information would have been either in tabular form or in a descriptive transcript? Perhaps, it would not have been possible from such a medium of communication to draw visual impressions which we get through these maps. Besides, it would also have been a time consuming task to draw inferences about whatever is being presented in non–graphical form. Hence, the graphs, diagrams and maps enhance our capabilities to make meaningful comparisons between the phenomena represented, save our time and present a simplified view of the characteristics represented. In the present chapter, we will discuss methods of constructing different types of graphs, diagrams and maps.

Representation of Data

The data describe the properties of the phenomena they represent. They are collected from a variety of sources (Chapter 1). The geographers, economists, resource scientists and the decision makers use a lot of data these days. Besides the tabular form, the data may also be presented in some graphic or diagrammatic form. The transformation of data through visual methods like graphs, diagrams, maps and charts is called representation of data. Such a form of the presentation of data makes it easy to understand the patterns of population growth,distribution and the density, sex ratio, age–sex composition, occupational structure, etc. within a geographical territory. There is a Chinese proverb that ‘a picture is equivalent to thousands of words’. Hence, the graphic method of the representation of data enhances our understanding, and makes the comparisons easy. Besides, such methods create an imprint on mind for a longer time.

General Rules for Drawing Graphs, Diagrams and Maps

1. Selection of a Suitable Method

Data represent various themes such as temperature, rainfall, growth and distribution of the population, production, distribution and trade of different  commodities, etc. These characteristics of the data need to be suitably representedby an appropriate graphical method. For example, data related to the temperature or growth of population between different periods in time and for different countries/states may best be represented using line graphs. Similarly, bar diagrams are suited best for showing rainfall or the production of commodities. The population distribution, both human and livestock, or the distribution of the crop producing areas may suitably be represented on dot maps and the population density using choropleth maps.

2. Selection of Suitable Scale

The scale is used as measure of the data for representation over diagrams and maps. Hence, the selection of suitable scale for the given data sets should be carefully made and must take into consideration entire data that is to be represented. The scale should neither be too large nor too small.

3. Design

We know that the design is an important cartographic task (Refer ‘Essentials of Map Making’ as discussed in Chapter 1 of the Practical Work in Geography, Part-I (NCERT, 2006), a textbook of Class XI). The following components of the cartographic designs are important. Hence, these should be carefully shown on The title of the diagram/map indicates the name of the area, reference year of the data used and the caption of the diagram.

These components are represented using letters and numbers of different font sizes and thickness. Besides, their placing also matters. Normally, title, subtitle and the corresponding year are shown in the centre at the top of the map/diagram. A legend or index is an important component of any diagram/map. It explainsthe colours, shades, symbols and signs used in the map and diagram. It should also be carefully drawn and must correspond to the contents of the map/diagram. Besides, it also needs to be properly positioned. Normally, a legend is shown either at the lower left or lower right side of the map sheet.

Direction

The maps, being a representation of the part of the earth’s surface, need be oriented to the directions. Hence, the direction symbol, i. e. North, should also be drawn and properly placed on the final map.

Excercises

1. Choose the right answer from the four alternatives given below:

(i) Which one of the following map shows the Population distribution:

    (a) Choropleth maps

    (b) Isopleth maps

    (c) Dot maps

    (d) Square root map

(ii) Which one of the following is best suited to represent the decadal growth of population?

    (a) Line graph

    (b) Bar diagram

    (c) Circle diagram

    (d) Flow diagram

(iii) Polygraph is constructed to represent:

    (a) Only one variable

    (b) Two variables only

    (c) More than two variables

    (d) None of the above

(iv) Which one of the following maps is known as “Dynamic Map”?

    (a) Dot map

    (b) Choropleth

    (c) Isopleth

    (d) Flow map

2. Answer the following questions in about 30 words:

    (i) What is a thematic map?

    (ii) Differentiate between multiple bar diagram and compound bar diagram.

    (iii) What are the requirements to construct a dot map?

    (iv) Describe the method of constructing a traffic flow map.

    (v) What is an Isopleth map ? How an interpolation is carried out?

    (vi) Describe and illustrate important steps to be followed in preparing a choropleth map.

    (vii) Discuss important steps to represent data with help of a pie-diagram

Please refer to attached file for NCERT Class 12 Geography Graphical Representation of Data