The position of an object on the surface of the Earth is usually given by its Longitude and Latitude, also known as geographic coordinates. Longitudes and Latitudes are angles measured from the centre of a theoretical sphere assumed to represent the Earth.Longitudes are horizontal angles while Latitudes are vertical angles. These angles are measured in degrees, minutes and seconds. A full circle is 360° and a straight angle is 90°. There is 60 minutes in one degree, and 60 seconds in a minute. The conventional notation for 12 degrees 25 minutes 17 seconds is 12°25'17".
The first figure views the Earth "from the top": Longitudes are measured from an arbitrary position known as the "Greenwich Meridian".
Eastern Longitudes values are increasing counter-clockwise to the East (ranging from 0°E to 180°E), and Longitude of places located West of the Greenwich Meridian are increasing clockwise, also from 0°W to 180°W.
Longitudes in Namibia are comprised between around 12°E ‘ (Kunene Mouth) and 25°E (Eastern Caprivi).
The second figure is a side view.
Latitudes are vertical angles measured from the Equator. Latitude range from 0°N at the equator to 90°N at the North Pole, and from 0° to 90°S at the South Pole. Latitudes in Namibia are comprised between 17°S (Kunene River) and 29°S (Orange River). Sometimes, Latitude in the Southern hemisphere are noted with negative values (Windhoek Latitude is –22°).
All points having the same Latitude are grouped on a line called parallel, because it is parallel to the Equator (blue lines on the figure).
Lines formed by points having the same longitude are called meridians (green lines on the figure). Meridians are not parallel to each other, as they converge to the poles.
Using geographic coordinates to define the location of one place is an absolute reference system. If you know the Longitude and Latitude of a place, you know exactly were it stays on Earth.
Because of this, Longitude and Latitude are used by the GPS system to display your position: on any GPS device, you can directly read your position in Longitude and Latitude