Data Representation on Maps – Geography – UGC NET – Notes

• The data describe the properties of the phenomena they represent. They are collected from a variety of sources. 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. T
• he 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

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 represented by 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.

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.

Design:

• We know that the design is an important cartographic task. The following components of the cartographic designs are important. Hence, these should be carefully shown on the final diagram/map.

Title:

• 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.

Legend:

• A legend or index is an important component of any diagram/map. It explains the 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.

Construction of Diagrams

The data possess measurable characteristics such as length, width and volume. The diagrams and the maps that are drawn to represent these data related characteristics may be grouped into the following types:

• One-dimensional diagrams such as line graph, poly graph, bar diagram, histogram, age, sex, pyramid, etc.;
• Two-dimensional diagram such as pie diagram and rectangular diagram;
• Three-dimensional diagrams such as cube and spherical diagrams. It would not be possible to discuss the methods of construction of these many types of diagrams and maps primarily due to the time constraint. therefore, described the most commonly drawn diagrams and maps and the way they are constructed. These are :
  1. Line graphs
  2. Bar diagrams
  3. Pie diagram
  4. Wind rose and star diagram
  5. Flow Charts

Line Graph

The line graphs are usually drawn to represent the time series data related to the temperature, rainfall, population growth, birth rates and the death rates.

Construction of a Line Graph:

1. Simplify the data by converting it into round numbers such as the growth rate of population as shown in Table for the years 1961 and 1981 may be rounded to 2.0 and 2.2 respectively. 
2. Draw 𝑋 and 𝑌-axis. Mark the time series variables (years/months) on the 𝑋 axis and the data quantity/value to be plotted (growth of population in per cent or the temperature in OC ) on Y axis.
3. Choose an appropriate scale and label it on 𝑌-axis. If the data involves a negative figure then the selected scale should also show it as shown in Fig.

4. Plot the data to depict year/month-wise values according to the selected scale on Y-axis, mark the location of the plotted values by a dot and join these dots by a free hand drawn line.

Year Growth rate in percentage: