Distributional Maps Class 9 Geography Notes Maharashtra State Board
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 the distribution of variables. Some maps are prepared with special themes. Such maps are called Thematic Maps. Through such maps, the distribution of various variables in a region is shown. The 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 on the variables. Distribution can be shown in the three following ways on a map:
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 the 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 is 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 the 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 systems, etc. of a region should be considered while placing dots on a map.
- While showing population distribution, the rural population is shown by dots, and circles are used to show the urban population.
- The dot method is most suitable for that variable which is freely scattered across the region.
Choropleth Method:
In these maps, the data regarding various geographical variables is shown by shades or tints of various colors. 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 patterns become darker with the increasing values of the given variable and are drawn accordingly on the map in the given classification.
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 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 subadministrative 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. Based on 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.
The following conclusions are drawn based on 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.
Geographical Field-Visit
Field visit is an important study method in geography. Geographical concepts and elements can be directly experienced through field visits. Field visits are extremely useful for understanding the correlation between humans and the environment.
Preparations for Field Visits:
Before going to the field visit, decide the place and the purpose of the visit. The elements which will be observed in field visits should be decided. Study the location map and the route map of the place to be visited. Distance, transport route, means of transport, and duration of field visit should be planned. With the help of teachers, students should prepare a questionnaire.
Selection of the Study Area:
A geographical field visit is organized for the study of various elements. e.g. physical landforms, river banks, dams, coastal areas, tourism sites, offices or museums related to geographical elements, villages, forest areas, etc. Elements should be selected after studying the local conditions and necessary permission letters have to be obtained. For a field visit, you should carry a notebook, specimen questionnaire, pen, pencil, scale, tape, compass, a bag for collecting samples, maps, camera, etc.
Precautions to be taken during field visit:
It is very important to ensure the safety of ourselves and others during a field visit. You should obey the instructions given by the teachers. You should not go to unknown remote places alone. During field visits, you should try to understand the local circumstances by conversing with the local people. You should also ensure that you do not harm the environment in any way during your visit. You should always keep a first-aid box with you for emergency circumstances.
Report-writing:
A field report should be written based on information obtained after the visit is complete. Use the following issues to make a report. Add photographs wherever necessary:
- Introduction
- Location Map and Route Map
- Physiography
- Climate
- Population
- Environmental Problems and Measures
- Land Utilization
- Conclusions
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