The horizontal line is known as the x-axis and the vertical line is known as the y-axis. Together the lines are called axes and the point where the two lines intersect each other is known as the origin.

Longitude is measured by imaginary lines that run around the Earth vertically (up and down) and meet at the North and South Poles. These lines are known as meridians. Each meridian measures one arcdegree of longitude. The distance around the Earth measures 360 degrees.

Get the coordinates of a place

1. On your Android phone or tablet, open the Google Maps app .
2. Touch and hold an area of the map that isn’t labeled. You’ll see a red pin appear.
3. You’ll see the coordinates in the search box at the top.

Every OS map has a grid, which is shown using faint blue lines. The lines across the bottom of the map are called eastings as they travel towards the east. The lines up the side of the map are called northings as they travel towards the north.

The thin brown lines snaking around a topographic map are called contour lines. All points along the same contour line are at the same elevation above sea level.

A grid is a network of a series of vertical and horizontal lines constructed perpendicular to each other. One series of lines runs from east to west and the other from north to south. Together they form squares of the same dimensions within a given map.

Hachured contour lines have tick marks added to them that point DOWNSLOPE. The standard rule states that “THE FIRST HACHURED CONTOUR LINE HAS THE SAME ELEVATION AS THE PRECEDING CONTOUR LINE.” The real problem comes about in determining which of the TWO ADJACENT contour lines is the PRECEDING contour line.

“Where a contact crosses a valley, it forms a “V”, the apex of which points in the direction of dip of the contact (Fig. 1 A,B).” Short, wide, open Vs indicate steep dips; longer, more narrow Vs indicate gentle dips.