This somewhat counter-intuitive definition is a result of the need for backward compatibility with existing latitude data, taken long before people had any idea of the Earth's oblation.
Originally, sextants were used to measure latitude based on solar elevation. This definition of latitude is easily measured by sextant: 90 degrees minus the maximum (i.e. noon) solar altitude on the equinox.
Originally, sextants were used to measure latitude based on solar elevation. This definition of latitude is easily measured by sextant: 90 degrees minus the maximum (i.e. noon) solar altitude on the equinox.