Notes-Class 9-Geography-Chapter-1-Distributional Maps-Maharashtra Board

Aim of maps : The main aim of maps is to show the location of a place and geographical distribution of variables.

Thematic maps : The maps that are prepared with special themes are called thematic maps.

Distributional maps : The maps showing the geographical distribution of temperature, rainfall, population, etc. are called distributional maps.

• Distributional maps are useful to explain the geographical distribution of various variables in a region.

Methods of showing geographical distribution in Geographical distributional maps : Distribution of various variables can be shown with the help of the following three methods : (a) Dot method (b) Choropleth method and (c) 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 the variable is distributed throughout the region, the dots are used to show its distribution on the dot map.
• To show the 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.
• In order to decide the number of dots and their values, the size of dot, the density of the variable and the scale of the map are taken into consideration. The size of a dot showing a same value is kept uniform.
• The physiography, water sources, transport system, etc. of a region are considered while placing dots on a map.
• The dot method is most suitable for that variable which is freely scattered across the region. (For example, population.)

Choropleth method :

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

Isopleth method :

• When the distribution of a variable is continuous, the isopleth method is then used to show its distribution. For example, altitude, temperature, rainfall, etc.
• In this method, the distribution is shown with the help of lines showing equal values. These lines are called isolines. For these maps, the accurate data regarding variables like altitude, temperature, rainfall, etc. is obtained.
• In this method, it is assumed that the difference between values of particular element of two places changes at a uniform rate.
• In this method, by considering the highest and the lowest values of the variable, the class intervals are decided to draw isopleths which in turn decides the difierence between the isolines.
• If isolines are closer to each other, then the change in the variable is steep and if the isolines are away from each other, then it is gentle. In this method, the sub-administrative units are not taken into consideration. By using isopleths method, we get an idea of the natural trend of the distribution of the variable.

Geographical field visit :

• Geographical field visit is an important study method in geography by which geographical concepts and elements can be directly experienced.
• Geographical field visits are extremely useful for understanding the correlation between humans and environment.

 Preparations for field visits:

The following things are included in preparations of field visits :

• Deciding the place and the purpose of the field visit.
• Deciding the elements which are to be observed in field visit.
• Studying the location map and the route map of the place to be visited.
• Planning about the distance, transport route, means of transport and duration of field visit, etc. Preparing questionnaire as per the purpose of the field visit.

Selection of the study area : The study area should be selected after studying the local conditions of the study area and obtaining the necessary permission letters.

Important materials required for field visit : For a geographical field visit, one should carry a notebook, specimen questionnaire, pen, pencil, scale, tape, compass, a bag for collecting samples, maps, camera, etc.

Precautions to be taken during geographical field visit :

• During a geographical field visit, it is very essential to obey all instructions of teachers.
• During a geographical field visit no one should harm the environment in any way.
• One should always keep a first-aid box for emergency circumstances.

Report writing :

• A field report should be written on the basis of information obtained after the field visit is complete. Photographs and relevant information must be added in the field report.

The field report can be written with the help of the following points :

• Introduction
• Location map and route map
• Physiography
• Climate
• Population
• Environmental problems and measures
• Land utilization
• Conclusions, etc.