What a map is: map, globe and sketch

Detail

1. The shape of the earth: why we need maps at all

• The earth's shape is a geoid. A geoid is an oblate spheroid, which means a ball that is slightly flat at the poles and bulges a little at the equator.
• The earth has three dimensions (length, breadth and height). Paper and screens have only two.
• The problem a map solves:
• You cannot lay a round surface flat without stretching or tearing it.
• So a map maker shrinks the earth, picks what to show and draws it on a flat sheet.

• The result is a two-dimensional picture of a three-dimensional earth.

• A smooth model of the earth's shape is used as the base for exact surveys. India's surveys used the Everest Ellipsoid, worked out by George Everest in 1830 from the Great Trigonometrical Survey [7].

2. Map: the definition, word by word

• Map (NCERT definition): a selective, symbolised and generalised drawing of the whole earth or part of it, on a plane (flat) surface, at a reduced scale.

Word in the definition	What it means in simple words
Selective	Only the features needed for the map's purpose are shown, such as roads on a road map or rivers on a drainage map.
Symbolised	Real things are shown by signs: lines, colours, dots and letters.
Generalised	Detail is simplified. A winding river becomes a smooth line, and a city becomes a dot.
Plane surface	The drawing is flat, on paper or a screen.
Reduced scale	Every distance is shrunk by a fixed amount. This is the map's scale, the ratio between a distance on the map and the same distance on the ground.

• Class 6 view (simple version):
• A map shows an area as seen from above (a bird's-eye view).
• An atlas is a book of maps.
• There are three main kinds of map:
  • Physical (relief) maps show natural features like mountains, plateaus, plains and rivers.
  • Political maps show countries, states, districts, cities and boundaries.
  • Thematic maps show one theme, such as rainfall, forests, roads or industries.

3. The three components of a map

• Distance: shown through the scale. Without a scale, you cannot work out real distances (scale is covered in detail in Ch 2, "Map Scale").
• Direction: most maps have an arrow marked N pointing to the north. The four cardinal directions are north, south, east and west. The intermediate directions are NE, SE, SW and NW.
• Symbols:
• A symbol is a small sign that stands for a real feature, such as a railway line, a temple or a well.
• Why symbols are used:
  • They save space, because a whole building cannot be drawn on a small sheet.
  • They follow a standard set agreed by everyone, so anyone can read the map, even without knowing the local language.
• In India, the Survey of India fixes these standard signs, called conventional signs, for its maps. They are covered in detail under topographical maps.

4. Globe: the true model and its limits

• Globe: a small round model of the earth.

• Because it has the same shape as the earth, a globe shows all four properties correctly: 1. shape of land and water bodies 2. size (area) 3. distance between places 4. direction

• Limits of a globe (why flat maps are still needed):

• It is costly to make.
• It is hard to carry, so you cannot fold it into a pocket or a field bag.
• It cannot show small details, such as a village, a street or a canal, because it is too small.

• You can see only half of it at a time.

• The trade-off:

• Flattening the globe's surface onto paper always distorts at least one of shape, size, distance or direction.
• Methods of doing this flattening are called map projections. They are covered in that chapter.

5. Sketch and sketch map: not a true map

• Sketch / sketch map: a drawing made freehand, without measuring.
• It has no true scale and no true orientation. Orientation means correct alignment with north.
• A network of lines and polygons (closed shapes) drawn without a scale is only a sketch, not a map.
• NCERT Fig. 1.2: "Sketch of the Environs of Delhi", shown next to "A Map of Delhi".
• The sketch gives the rough layout and order of places.

• The map gives correct distances and directions because it is drawn to scale.

• Use of a sketch: quick field notes, giving directions to a friend, or an exam answer drawing. It is useful, but you cannot measure from it.

Feature	Globe	Map	Sketch map
Shape of surface	Round, 3-D	Flat, 2-D	Flat, 2-D
Scale	True, uniform	True, stated (but projection distorts it)	None / not true
Orientation	True	True (north arrow)	Not true
Shape, size, distance, direction	All four correct	At least one distorted	Rough only
Detail	Very little	Little to very high (depends on scale)	Rough
Cost and portability	Costly, bulky	Cheap, easy to carry	Cheapest, made quickly
Typical use	Whole-earth view, teaching	Planning, navigation, administration	Rough layout, field notes

6. How map-making grew: ancient times to digital maps

a) Ancient maps

• Babylonian World Map: the first known world map. It is cut into a cuneiform clay tablet from about 600 BCE. Cuneiform is an ancient writing system of wedge-shaped marks [4][5].
• Babylon spanned modern Iraq, between the Tigris and Euphrates rivers. The map puts the city of Babylon at the centre of the world [5].
• It shows two concentric rings (circles with the same centre). A band marked "Salt [or Bitter] Sea" surrounds the cities [5].

• Lesson: this is a world-view drawing, not a measured map. It is closer to a symbolic sketch.

• Claudius Ptolemy (Greek scholar) wrote the Geography in about 150 CE [6].

• It listed more than 8,000 places known to the Greco-Roman world, centred on the Mediterranean [6].
• It placed locations using a system of latitude and longitude, so Ptolemy is often called the "father of geography" [6].
• In the 15th century it was translated from Greek into Latin and copied widely across Europe [6].
• Lesson: this was the move from drawing places to fixing them with a grid. That grid is the base of every true map.

b) Indian traditions

• Ancient Indian scholars wrote about the earth's shape, size and position in astronomy texts. Two examples are Aryabhata and Varahamihira.
• In the Mughal period, Abul Fazl's Ain-i-Akbari recorded detailed facts on the regions of the empire.
• The Puranas described the world as seven concentric dvipas (islands) separated by oceans. This was a world-view diagram, like the Babylonian one, not a scaled map.

c) Survey of India (1767): scientific mapping

• The Survey of India, set up in 1767, is the oldest scientific department of the Government of India. It has more than 250 years of mapping history [2].
• It is India's National Survey and Mapping Organisation and produces topographical maps for development, defence and administration [2].
• Great Trigonometrical Survey (GTS):
• What it measured: in 1802, surveyors began measuring a great arc along the 78° E meridian, starting from St. Thomas Mount, Madras (Chennai) [7].
• How triangulation works:
  • First, measure one base line of known length.
  • From its two ends, measure the angles to faraway points.
  • Join these into a network of triangles. Distances can then be worked out by calculation [8].
• Result: from 1802 to 1843, a network of large interlocking triangles covered the subcontinent and gave fixed control points in all directions. The project was named the GTS in 1818 [7].
• People: William Lambton and Sir George Everest led this work [3].

• Key result: the survey found that Peak XV, later named Mount Everest, is the world's highest mountain [8].

• At Independence (1947), India inherited a survey network of north–south and east–west trigonometric series. It was among the best geodetic control networks in the world. Geodetic means measuring the earth's exact shape and positions on it [3].

d) Digital maps (present day)

• National Geospatial Policy, 2022: notified on 28 December 2022. Geospatial data made with public funds is to be openly accessible [9].

• Target by 2030: a high-resolution topographical survey and mapping system and a highly accurate Digital Elevation Model (DEM) for the whole country [9]. A DEM is a digital map of land heights.

• The Survey of India has launched a pan-India CORS network (Continuously Operating Reference Stations). These are fixed GPS stations that give very accurate location data [9].

• Bhuvan is ISRO's geoportal (a map website), run by NRSC. It lets anyone view satellite (remote sensing) data and download some data free of cost. Government departments can also host their own map applications on it [10].
• Map-making has moved from clay → paper → GIS (Geographic Information System: computer layers of mapped data) and satellite imagery. The definition is still the same: selective, symbolised, generalised and scaled.

Prelims Hooks

• NCERT definition of a map: a selective, symbolised and generalised drawing of the earth or part of it on a plane surface at a reduced scale.
• Shape of the earth = geoid / oblate spheroid: flattened at the poles and bulging at the equator.
• Only a globe shows shape, size, distance and direction all correctly. Every flat map distorts at least one of them.
• Trap: a drawing with no scale and no true north is a sketch, not a map, even if it looks neat.
• Three components of a map: distance (scale), direction, symbols. India's conventional signs are fixed by the Survey of India.
• Survey of India: 1767. It is the oldest scientific department of the Government of India [2].
• GTS: started in 1802 along the 78° E meridian from Madras. Named "Great Trigonometrical Survey" in 1818. Found Peak XV = Mount Everest [7][8].
• Everest Ellipsoid: worked out by George Everest in 1830 [7].
• First known world map = Babylonian clay tablet, about 600 BCE, with Babylon at the centre [4][5]. Ptolemy's Geography = about 150 CE, more than 8,000 places, latitude–longitude [6].
• National Geospatial Policy 2022 (notified 28 Dec 2022): high-resolution topographic mapping and a national DEM by 2030 [9]. Bhuvan = ISRO/NRSC geoportal [10].

Mains Points

• Why a globe cannot replace maps (GS-I):
• A globe is the only true model, but it is costly, bulky and has too little detail.
• So planning, defence and administration depend on flat maps.

• Every flat map gives up some accuracy through projection. The choice of map depends on its purpose.

• Colonial survey as a tool of state-building:

• The Survey of India (1767) and the GTS (1802–1843) turned the subcontinent into measured, governable space for revenue, the army and railways.

• Independent India inherited one of the world's best geodetic networks [2][3][7].

• From paper to geospatial data (GS-III link):

• The National Geospatial Policy 2022 opens up publicly funded data. The CORS network and a national DEM by 2030 aim at accurate digital maps [9].
• Uses include land records, disaster mapping, urban planning and infrastructure.

• Bhuvan gives free access to satellite data [10].

• Maps as knowledge and as world-view:

• Early maps placed the maker's world at the centre: Babylon on the clay tablet, Mount Meru in the Puranic dvipas.
• Ptolemy's latitude–longitude grid marked the shift from symbolic drawings to measured maps [5][6].