reduction in latitude

reduction in latitude

The difference between the geocentric and the geographic latitudes of a place. The geocentric latitude is the smaller angle made by a line joining the place and the center of the earth with the plane of the equator, whereas the geographic latitude is the smaller angle made by the normal to the spheroid meridian at a place with the plane of the equator. The geocentric latitude can be obtained by subtracting the reduction in latitude from the geographic latitude. The maximum value of reduction in latitude is 11.6” of arc, and it occurs at 45° of latitude. For other latitudes, the reduction in latitude is equal to 11.6 sine λ sine 2°, where λ is the latitude. This occurs because the earth is an oblate spheroid rather than a true sphere.