Geocentric and Geodetic Latitude

In this post, we would learn the difference between Geocentric and Geodetic latitudes. In our earlier post, we had broadly seen about the definition and the importance of Parallels of Latitude in defining a position.


As we had seen in the case of latitude, when we draw a line from any point on the earth’s surface to the centre of earth and measure the angle this line makes with the plane of the Equator we get the Geocentric Latitude.

We are aware that the shape of earth is not perfectly spherical. The curvature of earth is more near the equatorial regions and lesser near the polar regions. Therefore, if you draw a line from any position on the surface of the earth to the centre of earth, you would find that the line is not perpendicular to the tangent at that point. In other words, centre of earth is not always directly below the perpendicular due to the Oblate Spheroid Shape of the Earth.


Since the curvature of earth is not uniform, instead of drawing a line joining the point to the centre of earth we draw the Normal at that point. This line would also intersect the Plane of Equator which could be displaced from the centre. It can be seen that the measured angle would be slightly different from the angle measured at the centre of the earth.

Latitude measured in this manner is called Geodetic Latitude and is the standard method used for producing aviation charts. The actual difference in Geocentric and Geodetic Latitude is very small and can be neglected. The maximum difference between Geocentric and Geodetic Latitude is just 11.6 minutes. The maximum difference occurs at approximately 45 degrees of North and South Latitude.

Until now, we have understood about the two types of latitude measurement. In our next post, we shall understand about the Meridians of Longitude.