What a map is

The earth's shape is a geoid, a three-dimensional shape best shown by a globe. A map turns that into two dimensions on a flat sheet, so it has to be drawn using a map projection and at a reduced scale. Imagine a plan of your school drawn at actual size: it would be as big as the campus.

Definition: a map is a selective, symbolised and generalised representation of the whole or part of the earth's surface on a plane surface at a reduced scale.

• Selective: only the features needed are shown.
• Symbolised: features are shown with symbols, colours and shades.
• Generalised: details are simplified to suit the scale and purpose.
• A network of lines and shapes without a scale is not a map, only a sketch: a freehand drawing that does not keep true scale or direction.

Five essentials of map-making (the steps of cartography, the art, science and technology of making maps):

• Scale: all maps are reductions, so the first decision is the scale. It limits how much information can be shown and how real it looks.
• Map projection: the system for turning the curved geoid into a flat surface. This always causes some unavoidable changes in direction, distance, area or shape.
• Map generalisation: every map has a purpose. A general purpose map shows relief, drainage, vegetation, settlements and transport; a special purpose map shows chosen themes such as population density or soils. The cartographer selects the relevant data and simplifies it.
• Map design: choosing symbols, their size and form, lettering style, line widths, colours and shades, the layout and the legend.
• Map construction and production: drawing and reproducing the map, once by hand with pen and ink, now with computer-assisted mapping and photo-printing.

From the video: the teacher shows the same area of Delhi at several scales, like zooming in on a phone map: as the scale gets larger, places like Connaught Place appear with more and more detail.

Example (new): a hand-drawn route to a friend's house that marks 'turn left at the big banyan tree, then the second lane' is a sketch, not a map: it has no scale, so you cannot measure how far anything is.