Maps and Map Scale

1. What a map is: map, globe and sketch

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• Map: a selective, symbolised and generalised drawing of all or part of the earth on a flat surface at a reduced scale (Class 11, Introduction to Maps). It turns the three-dimensional earth into a two-dimensional picture.
• The earth's shape is a geoid (an oblate spheroid, a ball slightly flattened at the poles).
• Globe: a model of the earth that shows shapes, sizes, distances and directions correctly. But it is costly and hard to carry, and it cannot show small details, so we need flat maps. Map-projections covers the limits of the globe in more detail.
• Sketch map: drawn freehand, with neither true scale nor true orientation. A network of lines and polygons with no scale is only a sketch, not a map (Fig. 1.2, the sketch of the area around Delhi next to a map of Delhi).
• Class 6 base: a map shows an area as seen from above. An atlas is a book of maps. Maps can be physical, political or thematic.
• A map has three components: distance (shown through scale), direction and symbols. Symbols save space and follow a standard set. In India, the Survey of India fixes these conventional signs (detail in topographical-maps).

2. Cartography and the essentials of map making

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• Cartography: the art, science and technology of making maps, and of studying and using them.
• The essentials of map making are five steps that every map goes through:

Step	What it means
1. Scale	The first decision. It limits how much detail a map can show and how real it looks (Fig. 1.3)
2. Projection	Turning the curved geoid into a flat surface. Some error in direction, distance, area or shape cannot be avoided (see map-projections)
3. Generalisation	Choosing data and simplifying it to fit the map's purpose and scale
4. Design	Planning how the map looks
5. Construction and production	Drawing and printing the map

• Map generalisation: keeping only what the map's purpose needs and simplifying it without spoiling its look. A general-purpose map shows relief, drainage, vegetation, settlements and transport. A special-purpose map shows one theme, such as population density. Smaller scales need more generalisation: houses merge into one settlement symbol, and a winding stream is drawn smoother.
• Map design: choosing symbols, lettering, line widths, colours and shades, and placing the title, legend, scale and north arrow.
• Map legend (key): the box that explains the colours, shades and symbols. It usually sits at the lower left or lower right.
• Production has moved from pen and ink with mechanical printing to computer-assisted mapping and photo-printing. Beyond NCERT: maps are now built digitally from satellite images and GIS layers (see remote-sensing-gis).

3. History of map making: the world and ancient and medieval India

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World

• The oldest known map is on a Mesopotamian clay tablet, about 2500 BC (Class 11, Introduction to Maps).
• Greek and Arab geographers laid the foundation of modern cartography. They measured the earth's circumference (Eratosthenes, about 240 BC, beyond NCERT) and used geographical coordinates.
• Ptolemy's map of the world (Claudius Ptolemy, Greek scholar, 2nd century CE; Fig. 1.4) was drawn on a grid of latitude and longitude.
• Beyond NCERT: al-Idrisi made a world map for Roger II of Sicily in 1154.
• In the early modern period, projections were made to give true direction, distance or area (Mercator 1569, see map-projections). In the 19th and 20th centuries, aerial photography added to ground survey.

India

• Map-making in ancient India: its roots lie in Vedic astronomy and cosmology. These ideas were set down in the siddhantas (laws) of Aryabhata, Varahamihira and Bhaskara. Scholars divided the known world into seven dwipas (Fig. 1.5). The Mahabharata imagined a round world surrounded by water (Fig. 1.6). For the Ujjayini prime meridian, see latitude-longitude-time.
• Medieval revenue mapping: Raja Todarmal (Akbar's finance minister) made land survey and map-making part of revenue collection. Sher Shah Suri's revenue maps improved the techniques further.

4. The Survey of India and modern mapping institutions

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• Survey of India: set up in 1767. Its intensive topographical surveys led to the map of Hindustan in 1785 (NCERT date; the map is linked with James Rennell, beyond NCERT). Today it maps the whole country at 1:250,000, 1:50,000 and 1:25,000.
• Beyond NCERT: it is India's oldest scientific department. It is based in Dehradun, works under the Department of Science and Technology (DST), and is headed by the Surveyor General.
• Map series: a set of maps made at the same scale, style and specifications, so that sheets placed side by side fit together. The Survey of India toposheets are an example (see topographical-maps).
• Great Trigonometrical Survey (GTS, beyond NCERT):
• It was begun in 1802 at Madras by William Lambton. It measured India by triangulation (fixing points with chains of triangles) along the Great Arc.
• George Everest continued it (Surveyor General 1830–1843).

• Radhanath Sikdar worked out about 1852 that Peak XV was the highest peak. It was named Mount Everest in 1865.

• Pundits: Indian surveyors trained in the 1860s to map Tibet in secret. They counted paces on prayer beads and hid their instruments. Nain Singh Rawat fixed the position of Lhasa.

• Geodetic datum: the model of the earth's shape used to fix coordinates. Old Indian maps used the Everest spheroid (1830). GPS and the Open Series Maps use WGS-84, so the same point can have slightly different coordinates on old and new sheets.
• National Atlas and Thematic Mapping Organisation (NATMO): based in Kolkata under DST. It was set up in 1956 as the National Atlas Organisation and renamed in 1978. It compiles the National Atlas of India and thematic maps.

5. Types of maps by scale: large-scale and small-scale

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• Large-scale map: shows a small area in great detail. Examples are topographical maps (1:250,000, 1:50,000, 1:25,000) and village maps, city zonal plans and house plans (1:4,000, 1:2,000, 1:500).
• Key trap: the bigger the denominator (the number after "1:"), the smaller the scale. So 1:4,000 is a larger scale than 1:250,000.
• Cadastral map (from the French cadastre, "register of territorial property"):
• It shows who owns each farm plot and each urban house, with field boundaries and a number for each parcel.
• Government makes it to collect revenue and taxes and to record ownership.
• Scale: villages at 1:4,000, city plans at 1:2,000 or larger (glossary range 1:500 to 1:4,000).

• Beyond NCERT: these maps are being digitised under the Digital India Land Records Modernisation Programme (DILRMP). Under SVAMITVA, village property is mapped by drone (verify current; see remote-sensing-gis).

• Topographical maps: fairly large-scale and based on precise surveys. National mapping agencies make them in series with uniform colours and symbols (see topographical-maps).

• Small-scale map: shows a large area with highly generalised detail.
• Wall map: printed on large paper or a plastic base for classrooms. Its scale is smaller than a topographical map's but larger than an atlas map's.
• Atlas map: very small-scale. NCERT calls it a "graphic encyclopaedia" of location, relief, drainage, climate, vegetation, towns, population, industry, transport and heritage sites.

6. Types of maps by function: physical and cultural

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• Physical map: shows natural features. Class 11, Introduction to Maps uses a series of maps of Nagpur district as examples:
• Relief map: general topography, such as mountains, valleys, plains, plateaus and drainage. It usually uses contours, layer tints or shading (Fig. 1.7, relief and slope).
• Geological map: geological structures and rock types (Fig. 1.8, rocks and minerals).
• Climatic map: climatic regions, and the spread of temperature, rainfall, cloudiness, humidity, and wind direction and speed (Fig. 1.9).

• Soil map: soil types and their properties (Fig. 1.10).

• Cultural map: shows features made by people.

• Political map: administrative divisions (country, state, district). It helps in planning and running these units.
• Population map: distribution, density and growth of population, and its make-up by age, sex, religion, language and occupation. NCERT calls it the most significant map for planning (Fig. 1.11).
• Economic map: crops, minerals, industries, markets and trade flows (Fig. 1.12, land use and cropping; Fig. 1.13, industries).

• Transportation map: roads, railways, stations and airports.

• Class 6 adds a third class, the thematic map. It overlaps with these classes, and how to draw one is covered in data-representation-thematic-maps.

7. Map scale: methods, systems of measurement and conversion

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• Map scale: the ratio between the distance between two points on a map and the real distance between the same two points on the ground.
• Metric system of measurement: 1 km = 1,000 m = 100,000 cm. India has used it since 1957, as do most countries.
• English system of measurement: 1 mile = 8 furlongs; 1 furlong = 220 yards; 1 yard = 3 feet; 1 foot = 12 inches. So 1 mile = 1,760 yards = 63,360 inches. The USA and the UK use it, and India used it before 1957 (Box 2.1).

Method	Example	Strength	Weakness
Statement of scale	1 cm represents 10 km	Simplest	Only users of that system can read it; it becomes wrong if the map is enlarged or reduced
Graphical scale (bar scale)	A bar with primary and secondary divisions	Stays valid when the map is enlarged or reduced	Readable only in its own units
Representative fraction (RF)	1:50,000	Has no units, so it is the universal method	Needs working out to read

• In an RF, the numerator (top number) is the map distance and the denominator (bottom number) is the ground distance. Class 6's "1 cm = 500 m" is a statement of scale.
• Conversion of scale (changing a scale from one method to another):
• 1 inch to 4 miles = 1 : (4 × 63,360) = 1:253,440
• 1:253,440 = 1 cm to 2.53 km

• 1:36,000 = 1 cm to 360 m = 1 inch to 1,000 yards

• How to draw a bar scale: 1. Take a line of about 15 cm (or 6 inches). At 1:50,000, 15 cm = 7.5 km. 2. Round off: 5 km = 10 cm. 3. Divide the line into 5 primary parts. 4. Split the left-hand part into secondary units (for example, 100 m each). 5. If the line length is awkward to divide, use the 40°–45° diagonal method (Fig. 2.4).

8. Using maps: distance, direction and area

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• Distance:
• Straight features (roads, railways, canals): measure with dividers or a ruler.
• Winding features (rivers, coastlines): lay a thread along the line, then straighten it and measure it.
• Rotameter: a small wheel that is rolled along a winding route.

• In every case, convert the reading into ground distance using the map scale.

• Direction: an imaginary line showing the angle from a base direction.

• North is the zero or base direction, and every map must show it.

• North line: the arrow on a map that shows north.

• Cardinal points: north, south, east and west. Between them lie the intermediate directions: NE, SE, SW and NW (Fig. 1.14; Class 6's eight-direction exercise).

• Area:
• Method of squares: put graph paper under the map. Area = (whole squares + partial squares ÷ 2) × map scale. It is simple but rough.

• Polar planimeter (Box 1.1): trace the boundary clockwise with the tracing arm. Take the difference between the dial readings before and after, and multiply it by the instrument's constant.

• Beyond NCERT: today GIS software measures lengths and areas directly (see remote-sensing-gis).

9. Who may map India: map policy from 2005 to the 2019 political map

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• National Map Policy 2005 (beyond NCERT) created two series of Survey of India maps:
• Defence Series Maps: full detail, for the armed forces.

• Open Series Maps: on the WGS-84 datum and UTM projection, with sensitive features removed, for public and development use (see topographical-maps).

• For decades, private mapping needed security clearances. The draft Geospatial Information Regulation Bill 2016 proposed licences and penalties for showing India's borders wrongly, but it was never passed.

• Guidelines for Acquiring and Producing Geospatial Data (15 February 2021, DST):
• Indian entities no longer need prior approval to collect, produce or publish maps, except for a negative list of sensitive attributes.
• The most accurate data is reserved for Indian entities.

• The National Geospatial Policy 2022 built on this (see remote-sensing-gis).

• New political map of India 2019: issued by the Survey of India on 2 November 2019 after Jammu and Kashmir was reorganised.

• It shows the Union Territories of Jammu and Kashmir and Ladakh.

• It places Gilgit-Baltistan and Aksai Chin in Ladakh.

• Rival maps drew Indian protests: Nepal's map of May 2020 (Kalapani, Lipulekh, Limpiyadhura) and China's "standard map" of August 2023 (see india-neighbours). India's external boundary is shown with the Survey of India's authority.

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Exam angles

Prelims — high-yield facts and traps

• Order of scale from largest to smallest: cadastral (1:500–1:4,000) > topographical (1:25,000–1:250,000) > wall map > atlas map. A bigger denominator means a smaller scale and more generalisation.
• RF is the universal method. Only the graphical scale stays valid when a map is enlarged or reduced. The statement of scale fails on both counts.
• The numerator is the map distance and the denominator is the ground distance.
• Key conversions: 1 mile = 63,360 inches; 1 km = 100,000 cm; 1 inch to 1 mile = 1:63,360; 1:100,000 = 1 cm to 1 km.
• NCERT exercise answers: 5 cm to 10 km = 1:200,000; 2 inches to 4 miles = 1:126,720; 1 cm to 100 m = 1:10,000; 1:31,680 = 1 inch to 4 furlongs; 1:50,000 = 1 cm to 500 m.
• The five essentials are scale, projection, generalisation, design, and construction and production. "History of maps is an essential of map making" is FALSE.
• "A network of lines without a scale is a map" is FALSE. It is a sketch.
• Survey of India 1767 (Dehradun, DST); map of Hindustan 1785; GTS 1802 (Lambton) and then Everest; Sikdar and Peak XV (about 1852); Nain Singh Rawat and Lhasa; NATMO in Kolkata (1956).
• Cadastral maps come from cadastre and record ownership and revenue. Todarmal and Sher Shah Suri were revenue mappers.
• The rotameter measures winding distance. The planimeter and the method of squares measure area.
• The oldest map is a Mesopotamian clay tablet (about 2500 BC). Ptolemy's map used a latitude-longitude grid.
• National Map Policy 2005: Defence Series and Open Series (WGS-84, UTM). The geospatial guidelines of February 2021 removed prior approval.

Mains — GS-I themes

1. Why scale is the first decision in cartography, and how it shapes generalisation and the uses of a map.
2. The Survey of India and the GTS in building India's territorial and scientific identity, including the role of Indian surveyors (Sikdar, the pundits).
3. Opening up geospatial data (2021 guidelines): gains for planning, start-ups and governance against national-security concerns.
4. Cadastral mapping and land-record modernisation as a base for land governance and for reducing disputes.
5. Cartographic aggression: how rival maps (Nepal 2020, China 2023) are used to press boundary claims.

Current-affairs hooks

• Survey of India's digital mapping, Open Series releases and online map portal (verify current).
• Drone-based village property mapping and land-record digitisation under SVAMITVA and DILRMP (verify current).
• Map releases by neighbouring countries and India's diplomatic protests.
• Private mapping firms and sector reforms under the 2021 guidelines and the 2022 policy.
• Anniversaries and exhibitions on the GTS and the pundits (Nain Singh Rawat).