Maharashtra Board Class 9 Geography Chapter 1 Distributional Maps PDF Download

Distributional Maps

You have studied district, state and country maps in the earlier classes in Environmental Studies and Geography subjects. The main aim of maps is to show the location of a place and distribution of variables. Some maps are prepared with special themes. Such maps are called Thematic Maps. Through such maps, distribution of various variables in a region is shown. Distribution of temperature, rainfall, population, etc. is shown on the map according to the data of these variables. These maps are useful to explain the distribution of these variables in the region. Such maps easily bring out the patterns of distribution. To draw distributional maps, we need statistical data of the variables. Distribution can be shown in the three following ways on a map:

Dot method, Choropleth method, Isopleth method

Dot Method

A dot map is prepared using statistical data. While preparing dot maps, only data gathered through counting is used. The way a variable is distributed throughout the region, the dots are used to show its distribution on the map. For example, the population of a region, the distribution of cattle, etc.

To show distribution through dot method, the value of a dot has to be determined. To do that, the lowest and the highest values of a given variable in a region are taken into consideration. Accordingly, the number of dots are determined. Also, we need to consider the size of the dot, the density of the variable and the scale of the map. The number of dots to be given for the value of variable in each sub-administrative unit needs to be decided first. The following precautions should be taken while using the dot method for a map:

The size of a dot should be uniform.

The distribution of physiography, water sources, transport system, etc. of a region should be considered while placing dots on a map.

While showing population distribution, rural population is shown by dots and circles are used to show urban population.

The dot method is most suitable for that variable which is freely scattered across the region.

In Fig. 1.1, the population distribution map of Amravati district is given. Answer the given questions by reading the distributional map shown by dot method:

What is the population of the Amravati town?

Teacher's Note

Dot maps help us see where people live in a district. In India, cities like Mumbai and Delhi have more dots because more people live there.

Exam Trick

Remember: Each dot = one fixed number of people. Count the dots carefully to find the total population. One dot is always the same size.

Points to Remember

Dot maps show how things are spread across a place.
All dots must be the same size.
Each dot stands for a fixed number of people.
We count dots to find the total population.
Dots show freely scattered things.

Choropleth Method

In these maps, the data regarding various geographical variables is shown by shades or tints of various colours. While making such maps, the data used for different variables is obtained through various processes such as measurement, surveying, etc. In this method, only one value is given to one sub-administrative unit in a region. The smallest and the largest values of the given data of the variable are taken into consideration. After that, 5-7 classes are made. Each class is assigned a tint of the same colour or black-and-white patterns. The shades or the patterns become darker with the increasing values of the given variable and are drawn accordingly on the map in the given classification.

In fig. 1.2 (A) and 1.2 (B), the population density maps of Amravati district using color shades and black-and-white patterns are shown. Read any one map in detail and answer the following questions:

Name the Talukas having population density between 301 and 400 persons per sq.km.

What is the density of the Amravati Taluka?

Name the Talukas having population density less than 300 persons per sq.km.

Teacher's Note

Choropleth maps use colors to show how population is spread. Dark colors show more people, light colors show fewer people. It is like painting areas based on how crowded they are.

Exam Trick

Remember: Darker shade = more people. Lighter shade = fewer people. Each area gets only one color or shade.

Points to Remember

Choropleth maps use colors and shades.
Darker colors show higher values.
Lighter colors show lower values.
Each area gets only one color.
We read the legend to understand the map.

Isopleth Method

You have seen contour maps and isobar maps in earlier classes. In these maps, the distribution was shown with the help of lines showing equal values. When the distribution of a variable is continuous, the isopleth method is then used to show its distribution. For example, altitude, temperature, rainfall, etc.

For these maps, we need to obtain the accurate data regarding the altitude, temperature, rainfall, etc. of some places in a region. It is assumed that the difference between the altitude or rainfall of two places changes at a uniform rate. The sub-administrative units are not taken into consideration here. Statistical data belongs to the respective places. Such data is known as point-related data.

Values of the variable are written on the map at their respective locations. If the data for more places is available, mapping of the distribution can be done more accurately. On the basis of this information, isopleth maps are prepared using the steps below:

By considering the highest and the lowest values of the variable, the class interval is decided to draw the isopleths maps which in turn decides the difference between the lines.

Lines are drawn for the decided intervals. Locations with the same value are joined by a line.

Following conclusions are drawn on the basis of the maps prepared in such a way.

If the lines are closer to each other then the change in the variable is steep and if the lines are away from each other, then it is gentle.

We get an idea of the natural trend of the distribution of the variable with the help of this map.

In fig. 1.3, the rainfall map of Amravati district is given. Read the map in detail and answer the questions.

In which part of the district is the rainfall more?

Teacher's Note

Isopleth maps show rainfall and temperature using curved lines. Places on the same line have the same rainfall. This is like the contour lines we see on hill maps.

Exam Trick

Remember: Lines close together = big change. Lines far apart = small change. Lines connect places with equal values.

Points to Remember

Isopleth maps use curved lines to show data.
Lines connect places with the same value.
Close lines show quick changes.
Far lines show slow changes.
These maps show things like rainfall and temperature.

This is a preview of the first 3 pages. To get the complete book, click below.