Although the marine sextant is seldom used these days due to the introduction of satellite navigation systems (ie GPS), it still can be used for the following:

1. Measuring the altitude of the stars, sun, moon and planets in order to determine geographical position out of sight of land (ocean navigation).
2. Measuring horizontal sextant angles between prominent terrestrial objects to fix position (coastal navigation).
3. Measuring vertical sextant angles of suitably positioned high terrestrial objects to obtain distance off (coastal navigation).
4. Vertical distances of masts to obtain distance off other ships when steaming in convoy (in times of conflict).
5. Hydrographic surveying.