Although the extents of latitude and longitude are same, i.e., 30° why is India’s north-south length longer than the east-west length by 300 km ?
[amp_mcq option1=”The alignment of the country is such that the north-south length is longer than its east-west length” option2=”The north-south length, which is measured along the meridian (great circle) is longer than the east-west length which is measured along the parallel close to the tropic of cancer (small circle)” option3=”The north-south and east-west lengths can not be compared, as the former is measured along the meridian and the latter along the parallel” option4=”The difference in length is due to variation in scale error along the meridian and parallel” correct=”option2″]
This question was previously asked in
UPSC CAPF – 2010
India’s approximate north-south extent is from about 8°N to 37°N (a difference of 29°), and the east-west extent is from about 68°E to 97°E (a difference of 29°). While the degrees of latitude and longitude are similar, the actual ground distance differs. The north-south distance is measured along meridians, which are effectively great circles, where 1 degree of latitude is approximately constant at 111 km. So, 29° latitude is about 29 * 111 km = ~3200 km. The east-west distance is measured along parallels of latitude. The length of a degree of longitude decreases with increasing latitude. At the Equator, 1 degree of longitude is about 111 km. At the Tropic of Cancer (around 23.5°N), which is close to the center of India’s east-west extent, 1 degree of longitude is significantly less than 111 km (~102 km). Further north, it is even less. Thus, 29 degrees of longitude across India’s width (which is primarily above the equator and around the Tropic of Cancer) covers a shorter distance than 29 degrees of latitude along its length. Option B correctly explains this by stating that the north-south length is measured along meridians (great circles) while the east-west length is measured along parallels (small circles) where the distance per degree of longitude is smaller than per degree of latitude.
The distance covered by a degree of latitude along a meridian is approximately constant, while the distance covered by a degree of longitude along a parallel decreases as latitude increases. India’s east-west extent is across latitudes where the distance per degree longitude is less than at the equator.