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Chapter 4 Maps
While a globe is useful for studying the Earth as a whole, it has limitations. It is difficult to study small areas like countries, states, or villages using a globe. In such situations, maps are used.
A map is a representation or drawing of the Earth's surface, or a part of it, on a flat surface (like paper) according to a scale. Although the Earth is round and cannot be perfectly flattened without distortion, maps are created to minimize this effect.
Maps are valuable for various purposes and can contain a lot of information. When many maps are collected and bound together, they form an Atlas. Atlases come in different sizes and scales.
Maps generally provide more detailed information about specific areas than a globe. They are of different types, categorized by the information they present.
Physical Maps
Physical maps, also known as relief maps, show the natural features of the Earth's surface. These features include mountains, plateaus, plains, rivers, oceans, and other geographical formations.
Political Maps
Political maps focus on human-made features and boundaries. They show cities, towns, and villages, as well as the boundaries of different countries and states of the world.
Thematic Maps
Thematic maps are designed to show specific information or themes. Examples include road maps, rainfall distribution maps, maps showing the distribution of forests or industries, etc. The title of a thematic map indicates the particular theme or information it represents.
Regardless of the type, there are three essential components of maps: Distance, Direction, and Symbol.
Distance
Maps are scaled-down representations of the Earth or a part of it that fit onto a piece of paper. They are drawn to reduced scales. This reduction is done precisely so that the ratio between the distance shown on the map and the actual distance on the ground is consistent. This ratio is called the scale of the map.
For example, if 2 cm on a map represents an actual distance of 10 km on the ground, the scale is $1 \text{ cm} = 5 \text{ km}$. Knowing the scale allows you to calculate the real distance between any two points on the map.
There are two types of scales commonly used:
- Small Scale Map: Used to show large areas like continents or countries on a small sheet of paper. A large actual distance is represented by a small distance on the map (e.g., 5 cm on the map represents 500 km on the ground).
- Large Scale Map: Used to show small areas like villages or towns on paper. A smaller actual distance is represented by a larger distance on the map (e.g., 5 cm on the map represents 500 meters on the ground).
Large scale maps provide more detailed information about a small area compared to small scale maps.
Example. Look at the Figure 4.1. There is a scale. It may be used for measuring distance between places. For example the distance between the well and the tree is 5 cm. It means that the actual distance is 50 metres. Now the distance between the PO (A) to Karim’s house (E) is 12 cm. It means 120 metres on the ground but you can not fly like a bird directly from E to A. You will have to walk on the road. Let us measure the total walking distance from E to C, then C to M, M to B and B to A. Add all these distances. This will be the total walking distance from Karim’s house to the post office.
Answer:
To find the total walking distance from Karim's house (E) to the post office (A) based on the example in Figure 4.1, you would need to measure the length of the road segments connecting these points on the map and use the given scale ($1\text{ cm} = 10\text{ metres}$). The example gives the direct distance as 12 cm on the map or 120 metres on the ground, but clarifies this isn't the walking distance. You would measure:
1. The distance on the map from E to C.
2. The distance on the map from C to M.
3. The distance on the map from M to B.
4. The distance on the map from B to A.
Add these measured distances (in cm). Then, multiply the total length in cm by the scale factor (10 metres/cm) to get the total walking distance in metres. For example, if E to C is 3 cm, C to M is 4 cm, M to B is 3 cm, and B to A is 2 cm, the total map distance is $3+4+3+2 = 12$ cm. The total walking distance would then be $12 \text{ cm} \times 10 \text{ metres/cm} = 120 \text{ metres}$. (Note: The example seems to suggest the walking distance in this specific case might be the same as the direct distance number, which is coincidental or illustrative based on hypothetical measurements).
Direction
Most maps include an arrow, usually in the upper right-hand corner, marked with the letter 'N'. This is the north line, indicating the north direction. Once you know north, you can easily determine the other main directions: South (opposite to North), East (to the right when facing North), and West (to the left when facing North).
The four main directions – North, South, East, and West – are called cardinal points {Figure 4.2 (a)}. In addition to these, there are four intermediate directions: North-East (NE), South-East (SE), South-West (SW), and North-West (NW). Using these intermediate directions helps in locating places more accurately.
A compass is an instrument specifically used to find the main directions. Its magnetic needle always points towards the north-south direction {Figure 4.2 (b)}.
Symbols
Symbols are the third crucial component of a map. It is impractical and often impossible to draw the actual size and shape of various features (like buildings, roads, trees, railway lines, wells) on a map drawn to scale. Therefore, these features are represented using standard symbols.
These symbols can be letters, shades, colors, pictures, or lines (Figure 4.3). They efficiently convey a lot of information within a limited space on the map. Using symbols makes maps easier to draw and simple to read. Maps have a universal language of symbols that can be understood regardless of the local language. Many of these symbols are standardized through international agreement and are known as conventional symbols.
Colors are also conventionally used to represent certain features. For instance, blue typically represents water bodies (lakes, rivers, oceans), brown is used for mountains, yellow for plateaus, and green for plains.
Sketch
A sketch is a drawing primarily based on memory and observations made on the spot, and it is not drawn to scale. Sometimes, a rough drawing of an area is needed to indicate the location of a specific place relative to other landmarks. For example, if you are giving directions to a friend's house, you might draw a rough map without precise measurements. Such a drawing is called a sketch map.
Plan
A plan is a drawing of a small area on a large scale. While a large-scale map provides significant detail, certain minute details like the exact length and width of a room cannot be accurately shown on it. In such cases, a drawing made to scale for a very small area, like a single room or a building, is called a plan.
In summary, maps are essential tools for representing the Earth's surface. Understanding their components – distance (scale), direction, and symbols – is key to reading and interpreting them effectively. Different types of maps serve different purposes, focusing on physical features, political boundaries, or specific thematic information. Sketches are rough drawings not to scale, while plans are detailed drawings of small areas on a large scale.