The map is the most important tool of a geographer for studying the distribution of various features on the earth. Maps are of various kinds showing different categories of information. Atlas maps of continents and oceans are general maps showing location of mountains, rivers and other physical features and cultural aspects like railways, roads, cities etc. Some atlases also contain maps showing climatic conditions soils, natural vegetation, economic aspects, etc. Wall maps used for instruction in classroom situations are generalized maps which are large in size so that features can be distinguished easily from a distance. Topographic maps are also general maps showing much more details than Atlas maps or wall maps. Each map shows a small area indicating the relief and drainage features, settlements, roads, railway lines, and other features of cultural landscape. Town maps and Village maps are called cadastral maps as they show boundaries of properties such as fields and house-sites.
Besides the general purpose maps indicated above there are specialized maps called thematic maps. They deal with a particular aspect, such as climate, distribution of population crops, industries, etc. These distribution maps may show location of features like mines, industries, cities etc. by point symbols like dot, square, triangle, cube, sphere etc. The size of the symbol may be proportional to the quantity of production or value. Population distribution may be represented by a dot map with each dot representing a proportion of population. Aerial features like rainfall crops cultivated indicating a given value, or rural population may be shown by isopleth or choropleth maps. In an isopleth map showing rainfall distribution, lines are drawn to join places receiving the same amount of rainfall. The space between the lines are shaded or coloured on a graded scale. The weather maps show atmospheric pressure by isobars. This is also an example of an isopleth map. A choropleth map is based on data for different administrative units like districts or states. A map showing the density of population on the basis of districts is an isopleth map. In a choropleth map the districts are shaded on the basis of density values.
Statistical Data
Another method of representing features of the earth is based on air photographs taken from aeroplanes. These air photographs are useful for making studies relating to land use in an area and survey of resources. More recently photographs from remote sensing satellites have also been used for a study of land use and other resources like soils, minerals, etc.
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