




18° 61,23' N  061° 13,76'W. Are these coordinates plausible ? 











When using Mercator projection one measures distances on 











The unit used at sea for distances is the Nautical Mile which represents 











After having calculated a course of 180° I want to give indications to the helmsman. The variation in the area is 10°W. What do I tell the helmsman ? 











The variation of the area is to be found 











Depth soundings are always indicated in meters. 











When using a navigational chart with depth soundings in fathoms and feet, what does a figure like 18,3 mean ? 











The height of the water in the harbour is 5,5m. How much water will I have on a sounding of 2,5 underligned ? 











All the points on the same Latitude form the 








