Change of Latitude

We will now look at what happens to the latitude, when we fly from one position to another on the earth’s surface in terms of the Change in the Latitude. In our earlier post we had learnt about the Latitude and Longitude Co-ordinate system for defining position accurately. In case you have missed it you may like to go through it before reading this post.

ChLat is an abbreviation for a change of Latitude during a flight from one Latitude to another Latitude. We have learnt that the Equator cuts the earth into two equal halves called Hemispheres. The Hemisphere North of Equator is called the Northern Hemisphere and the one South of Equator is called Southern Hemisphere.

Latitude is defined as the angle measured between the Normal at a Place to the Plane of Equator. It is expressed in terms either North or South of the Equator. A combination of Latitude and Longitude provides a very accurate system to locate positions on the surface of the earth.

If we were to move from the Equator which is 0 degree Latitude to 30 degree North, we would have travelled through 30 degrees of Latitude in the Northerly direction. In other words, the ChLat would be 30 Degrees North.


There are some special lines of Latitude on the earth. These are the Arctic Circle (N66 1/2), Tropic of Cancer (N23 1/2), Equator (NS 00) , the Tropic of Capricorn (S23 1/2) , and Antarctic Circle (S23 1/2) .

The change in Latitude (Ch Lat) from the Equator to the Tropic of Capricorn would be 23 1/2 degrees in a Southerly Direction. Similarly, from the Tropic of Capricorn to the Antarctic Circle the Ch Lat would be another 43 degrees in a Southerly Direction.

If we go from the Tropic of Capricorn to the Arctic Circle, we would have 23 1/2 degrees to go to the Equator and then a further 66 1/2 degrees to go to the Arctic Circle. The Ch Lat would therefore be a total of 90 degrees in a Northerly Direction.

Let us now calculate the ChLat from S3030 to N4030. From 3030S to Equator would be 29 degrees 30 minutes to the North, Thereafter from Equator to 4030N would be 40 degrees 30 minutes North. Total ChLat would be an addition of these two values, which would be 70 degrees in the Northerly direction.

In Air navigation, the value of ChLat would be frequently used to solve many navigation problems. Therefore, as Student Pilots, you need to practice calculation of Ch lat. In our next lesson, we shall understand about the Change of Longitude.