What type projection is used by ship navigators? and why?

The Mercator Projection, invented in 1569 by Gerardus Mercator. They used this because of it can chart the navigator's course on the Mercator Projection with a straight line. It also had a unique design and "idea."

Mercator and Lambert projections are commonly used by (Ship) navigators and aircraft pilots and navigators, supplemented by GPs and other electronic aids. the Lambert system produces a compact circular (sectional) chart easily slipped into instrument housings like bomb sights, drift meters, etc, it is graduated in azimuth, hence making targeting of landmarks easy. in soe models the operators make adustemnts to keep the target destination in the center of the cross hairs- this is on a map, not the actual ground. the projection is as similar as possible so when the Bombardier takes the sights- the image will be familiar i just know that much about this topic 
I hope it helped you :-)

Canada and

Most topographic maps, the index contour lines are generally darker and are marked with their elevations.