In order to find out the absolute location of a place on the map, which of the following will be required?

Correct — C, Both latitude and longitude of the place. Absolute location means the one position on the globe a place occupies, stated without reference to anything else. Latitude on its own places a point somewhere on a parallel — a complete circle running right round the Earth — and longitude on its own places it somewhere on a meridian, a half-circle from pole to pole. Each line is an infinite set of points. It is only where a particular parallel crosses a particular meridian that a single position is fixed, which is why every coordinate on a map is quoted as a pair.

• (a)Latitude of the place alone — Latitude alone leaves the place anywhere on a circle of latitude. Every point on the Tropic of Cancer shares the same latitude while lying in different countries and different oceans.
• (b)Longitude of the place alone — Longitude alone leaves the place anywhere along a meridian running from the North Pole to the South. The 82°30' E meridian passes through several Indian states before continuing far beyond them.
• (d)Neither latitude nor longitude of the place — Without either coordinate no absolute position can be given at all. What remains is relative location — describing a place by its position with respect to another, which is a different idea.

Latitude is angular distance north or south of the equator, from 0° at the equator to 90° at the poles, and its lines are parallels. Longitude is angular distance east or west of the prime meridian at Greenwich, from 0° to 180°, and its lines are meridians converging at the poles. The two together form the graticule, and the pair of values is the absolute location of a point. Relative location, by contrast, describes where a place is in relation to another place.

The item is short but it separates two ideas that are easy to blur. Latitude is not a point and longitude is not a point; each is a line, and lines intersect at points. A candidate who sees the geometry does not need to remember the definition. The practical version of the same reasoning is Indian Standard Time, which is set by the 82°30' E meridian — a meridian identifies a time zone, but it takes a latitude as well to say where on that meridian a place lies.

• Latitude is angular distance north or south of the equator; its lines are parallels.
• Longitude is angular distance east or west of the prime meridian; its lines are meridians.
• Absolute location is the pair of coordinates; relative location describes position with respect to another place.
• The equator is the longest parallel and the only great circle among them; all meridians are halves of great circles.
• India's standard meridian is 82°30' E, passing near Mirzapur in Uttar Pradesh.

• Treating a single coordinate as sufficient to identify a place.
• Confusing absolute location with relative location.
• Reversing the definitions and calling the parallels lines of longitude.

A definition item on map reading, and the base for the time-calculation questions that appear across all these papers.

• practice — not a real PYQ

  Lines of longitude are also called

  • (a)parallels
  • (b)meridians
  • (c)isotherms
  • (d)contours

  Answer(b) meridians — parallels are the lines of latitude.

• practice — not a real PYQ

  The absolute location of a place is best given by

  • (a)its distance from the nearest city
  • (b)its latitude and longitude
  • (c)its height above sea level
  • (d)the direction of the nearest river

  Answer(b) its latitude and longitude — the other three describe relative position or elevation.