Chapter 1 Introduction To Maps

Maps are familiar tools used to represent the Earth or parts of it, commonly seen in various books and resources. Unlike a globe, which best represents the Earth's three-dimensional, slightly irregular shape (geoid), a map is a simplified depiction on a flat surface, typically a piece of paper.

An image representing the Earth as a globe, showing India on its curved surface.

Effectively, a map is a two-dimensional representation of the Earth's three-dimensional surface. Because the Earth's surface is curved, representing it accurately on a flat map requires using a system of map projections, which mathematically transform the spherical surface onto a plane.

Maps are drawn at a reduced scale because it's impossible to show features of the Earth's surface in their actual size. A map's scale defines the relationship between distances on the map and corresponding distances on the ground. Features on a map are also simplified and represented using conventional symbols, colours, and shades.

Therefore, a map can be defined as a selective, symbolised, and generalised representation of the whole or part of the Earth's surface on a plane surface at a reduced scale. A drawing of lines and polygons without a defined scale is considered a sketch, not a map (Figure 1.2 compares a sketch to a map).

Comparison of a freehand sketch (without scale or consistent orientation) and a formal map (with scale, symbols, and orientation).

Understanding maps involves knowing their essential components, different types, and various uses.

Glossary terms introduced in the text:

• Cadastral Map: A large-scale map showing property boundaries.
• Cardinal Points: The four main directions: North, South, East, West.
• Cartography: The art, science, and technology of map making and using maps.
• Generalisation - Map: Simplifying map features appropriate to the scale or purpose.
• Geoid: The actual shape of the Earth, an oblate spheroid.
• Map: Selective, symbolised, generalised representation of Earth on a flat surface at a reduced scale.
• Map series: A set of maps of an area produced with consistent specifications.
• Projection - Map: System for transforming the spherical Earth surface onto a plane.
• Scale: Ratio between map distance and ground distance.
• Sketch Map: A freehand map without true scale or orientation.

Essentials Of Map Making

Regardless of their type or purpose, all maps share certain fundamental requirements and involve common processes in their creation (Cartography). These essential elements of map making are:

• Scale
• Map Projection
• Map Generalisation
• Map Design
• Map Construction and Production

Scale: Since maps represent a large area on a smaller surface, they are always reductions of reality. The first critical decision in map-making is choosing the appropriate scale. The scale determines the level of detail and the amount of information that can be effectively shown on the map. A larger scale allows for more detail of a smaller area, while a smaller scale shows less detail but covers a larger area (Figure 1.3 demonstrates the effect of scale on the visible information).

Example maps illustrating how increasing the scale (showing a smaller area) allows for more detailed representation of features, while decreasing the scale (showing a larger area) requires generalisation.

Projection: Representing the Earth's curved, three-dimensional surface (geoid) on a flat, two-dimensional plane introduces distortions. A map projection is the systematic transformation of points from the spherical surface to the plane surface. This transformation inevitably alters the true relationships of direction, distance, area, and shape. The choice and use of a suitable projection are crucial in map-making, depending on the map's purpose (e.g., a projection might preserve area but distort shape, or vice versa).

Generalisation: Every map is created to serve a specific purpose, whether it's a general map showing various features or a special map focusing on a single theme (like population density or soil types). Because maps are drawn at a reduced scale and for a specific purpose, the cartographer must decide what information to include and how to simplify it. Map generalisation involves selecting the data relevant to the map's theme and simplifying features to suit the chosen scale and purpose, ensuring visual clarity and appropriateness without sacrificing essential information.

Map Design: This involves planning the visual aspects of the map to ensure effective communication. It includes selecting appropriate symbols (size, shape, style), choosing lettering styles, determining line widths, selecting colours and shades to represent different features, and arranging all map elements (map body, title, legend, scale bar, north arrow) in an aesthetically pleasing and functional layout. Good map design is governed by principles of graphic communication to make the map easy to read and interpret.

Map Construction and Production: This is the process of actually drawing the map and reproducing it. Traditionally, maps were drawn by hand using pen and ink and then printed mechanically. Modern cartography has been transformed by technology, with extensive use of computer-assisted mapping software for drawing and digital printing techniques for production.

History Of Map Making

The practice of map making has a long history, dating back to ancient times. The earliest known map, drawn on a clay tablet, was found in Mesopotamia and dates back to around 2,500 B.C. Early cartography saw significant contributions from Greek and Arab geographers, who developed concepts like measuring the Earth's circumference and using geographic coordinates (latitude and longitude) for map-making.

A historical map, such as Ptolemy's depiction of the known world, showcasing early cartographic understanding.

In the early modern period, cartography saw a revival. Increased exploration and scientific understanding led to efforts to minimize the distortions introduced when projecting the curved Earth onto a flat surface. Maps were drawn using different projections designed to preserve specific properties like directions, distances, or areas accurately. The advent of aerial photography in the 19th and 20th centuries provided a new method for gathering spatial data, complementing ground surveys and stimulating further advancements in map-making.

In India, the roots of map making can be traced back to the Vedic period, connected with astronomical and cosmological concepts. Ancient Indian scholars like Arya Bhatta, Varahamihira, and Bhaskara developed mathematical and astronomical principles reflected in their works. Ancient Indian cosmology sometimes depicted the known world as seven 'dwipas' or islands (Figure 1.5) or conceived of a round world surrounded by water (Figure 1.6, as in the Mahabharata).

An illustration representing the ancient Indian concept of the world divided into seven island continents (dwipas).

An illustration representing the ancient Indian cosmological concept of a round world encompassed by water.

During the medieval period, figures like Todarmal made land surveying and map-making integral to revenue collection systems. Sher Shah Suri also contributed to revenue mapping techniques. The establishment of the Survey of India in 1767 marked a significant step towards systematic topographical surveys and the creation of accurate maps for the entire country, culminating in maps like the one of Hindustan in 1785. Today, the Survey of India remains the national mapping agency, producing maps at various scales.

Types Of Maps Based On Scale

Map scale is a primary basis for classifying maps. Based on the ratio between distances on the map and corresponding distances on the ground, maps are generally divided into two categories:

• Large-scale Maps: Show small areas with a high level of detail. They use a relatively large representative fraction (e.g., 1:4,000, 1:25,000).
• Small-scale Maps: Show large areas with less detail. They use a relatively small representative fraction (e.g., atlas maps, wall maps).

Large-scale Maps

These maps depict smaller areas in greater detail due to their larger scale. They are further divided into:

• Cadastral Maps: Derived from the French word 'cadastre' (register of territorial property). These are very large-scale maps (e.g., village maps at 1:4,000, city plans at 1:2,000 or larger) primarily used to show property boundaries, land ownership, and plot numbers for administrative purposes like revenue collection and recording land rights.
• Topographical Maps: Prepared based on detailed and precise ground surveys. They are typically part of a map series produced by national mapping agencies (like the Survey of India). Topographical maps are drawn at fairly large scales (e.g., 1:250,000, 1:50,000, 1:25,000) and provide detailed information about both natural features (relief, drainage, vegetation) and man-made features (settlements, roads, railways, services like schools, post offices), using standardized symbols and colours.

Small-scale Maps

These maps represent larger geographical areas with a lower level of detail due to their smaller scale. They are divided into:

• Wall Maps: Generally drawn on large paper or plastic sheets designed for display in classrooms or lecture halls. Their scale is smaller than topographical maps but larger than atlas maps, making them suitable for showing large areas while still being legible from a distance.
• Atlas Maps: Very small-scale maps found in atlases. They cover very large areas (continents, countries, the world) and provide a highly generalised representation of features. Atlases serve as condensed graphical encyclopedias of geographical information on various themes (location, relief, climate, population, resources, etc.) at a broad level.

Types Of Maps Based On Function

Maps can also be classified based on their specific purpose or the type of information they show. This classification broadly distinguishes between maps showing natural features and maps showing man-made or human-related features.

Physical Maps

These maps depict natural features and phenomena of the Earth's surface. Examples include:

• Relief Maps: Show the general topography, including mountains, valleys, plains, plateaus, and drainage patterns (Figure 1.7 shows a relief map).

A physical map specifically illustrating the variations in elevation and slope across the Nagpur district.

• Geological Maps: Illustrate the distribution of different geological structures, rock types, and sometimes mineral deposits (Figure 1.8 shows a geological map).

A physical map depicting the different types of rocks and the locations of mineral deposits found within the Nagpur district.

• Climatic Maps: Show climatic regions or the distribution of specific climatic elements such as temperature, rainfall, cloud cover, humidity, wind direction, and wind speed (Figure 1.9 shows a climatic map).

A physical map illustrating specific climatic conditions or parameters for the Nagpur district.

• Soil Maps: Represent the distribution of different soil types and their characteristics or properties (Figure 1.10 shows a soil map).

A physical map displaying the distribution of different soil types across the Nagpur district.

Cultural Maps

These maps illustrate man-made or human-related features, activities, and distributions. Examples include:

• Political Maps: Show administrative divisions such as countries, states, districts, and their boundaries. They are useful for administrative planning and management.
• Population Maps: Depict various demographic characteristics of the population, such as distribution patterns, density, growth rates, age and sex composition, distribution of social, religious, or linguistic groups, and occupational structure (Figure 1.11 shows a population distribution map). Population maps are essential tools for planning and development initiatives in an area.

A cultural map illustrating how the population is distributed spatially across the Nagpur district.

• Economic Maps: Show the spatial patterns related to economic activities, including the production and distribution of crops, minerals, and industrial goods, location of industries and markets, and transportation routes for trade and commodity flow (Figures 1.12 and 1.13 show economic maps).

A cultural map showing how land is used for different purposes and the distribution of various cropping patterns in the Nagpur district (an example of an economic map).

A cultural map indicating the geographical location of industrial units or zones within the Nagpur district (an example of an economic map).

• Transportation Maps: Illustrate transportation networks, including roads, railway lines, locations of railway stations, airports, and sometimes shipping routes or ports.

Uses Of Maps

Maps are fundamental tools for geographers, planners, environmental scientists, and many other professionals. They are used to visualize spatial information and perform various measurements related to geographical features.

Measurement Of Distance

Maps allow for measuring the distance between points or along linear features. Linear features on maps can be straight (e.g., roads, railway lines, canals) or erratic/curved (e.g., coastlines, rivers). Measuring straight lines is straightforward using a ruler or dividers and applying the map scale.

Measuring distances along irregular lines requires different techniques:

• Using a thread: Place a thread along the curved line on the map, then straighten the thread and measure its length with a ruler. Apply the map scale to convert the map distance to ground distance.
• Using a Rotameter: A mechanical or digital instrument with a small wheel. The wheel is traced along the line on the map, and the instrument records the distance covered. This distance is then converted to ground distance using the map scale.

Measurement Of Direction

Direction refers to the angular position of one point or feature relative to another, typically measured from a standard base direction, usually North. A map always indicates the North direction (e.g., with a North arrow or by aligning with meridians). All other directions are determined in relation to North.

The four main or cardinal points are North (N), South (S), East (E), and West (W). Intermediate directions include Northeast (NE), Southeast (SE), Southwest (SW), and Northwest (NW) (Figure 1.14 shows cardinal and intermediate directions). Directions can also be measured more precisely as angles in degrees (e.g., $90^\circ$ East of North).

Diagram illustrating the four cardinal directions (North, South, East, West) and common intermediate directions (Northeast, Southeast, Southwest, Northwest).

Measurement Of Area

Maps enable the measurement of the area of geographical features, such as administrative regions, lakes, forests, or agricultural fields. Several methods are used for area measurement on maps:

• Using a grid of squares: Overlay the area to be measured with a grid of squares (like graph paper). Count the number of 'whole squares' completely within the area. Count the 'partial squares' along the boundary (often estimating them or counting squares that are more than half inside). The total area is calculated using the formula: $Area = (\text{Sum of whole squares} + \frac{\text{Sum of partial squares}}{2}) \times (\text{Map Scale})^2$. The map scale is squared because area involves two dimensions.
• Using a Planimeter: A mechanical or digital instrument used to measure area by tracing the perimeter of the shape on the map. A polar planimeter, for example, measures the area based on the movement of a tracing arm as the operator follows the boundary of the area. The instrument gives a reading in its own units, which are then converted to actual area units using a constant specific to the instrument and the map scale. This method is generally more accurate than the grid method.