Practical Work in Geography | Class 11 Geography Notes

Latitude, Longitude and Time

The Earth is nearly spherical but not a perfect sphere. Its equatorial radius is larger than its polar radius due to the Earth's rotation causing a bulge at the equator, making its shape an oblate spheroid. This shape presents challenges in accurately positioning surface features because there is no fixed reference point on the surface. To overcome this, a network of imaginary lines is drawn on globes and maps to locate places precisely. These lines form the geographical grid, consisting of two sets of lines: parallels of latitude and meridians of longitude.

The Earth spins on its axis from west to east, creating two natural reference points: the North Pole and the South Pole. These poles form the basis of the geographical grid. The horizontal lines, called parallels of latitude, run east-west and are parallel to each other. The equator is the most important parallel, drawn midway between the poles, and divides the Earth into the Northern and Southern Hemispheres. It is the largest circle on the globe and is called a great circle. Other parallels are smaller circles (small circles) that decrease in size as they move towards the poles.

Vertical lines running north-south are called meridians of longitude. They join the two poles and are widest apart at the equator, converging at the poles. Together, these lines provide a coordinate system that helps in determining the location, distance, and direction of places on Earth. Latitude and longitude are measured in degrees (°), with each degree subdivided into 60 minutes (′) and each minute into 60 seconds (″).

📊 Diagram: Figure 3.1 shows the parallels of latitudes as horizontal circles on the globe, with the equator as the largest circle. Figure 3.2 illustrates the drawing of parallels of latitudes on a circle using a protractor, marking angles from the equator.

🔗 Connection: This section introduces the fundamental concepts of latitude and longitude, which leads to detailed explanations on how to draw parallels and meridians and their significance in determining time.