Question

The mercator projection, which you read about, is a popular map for plotting courses. what one characteristic of this projection remains true or undistorted no matter where you are on a map of this type?

Answer 1

One of the Characteristic is The rhumb lines are constant.
On every Mercator projection maps, any rhumb line will always be a straight line; witht he assumption that the map had 360 degrees of longitude)
The projection of south and north pole on this projection  occur at infinity.