prize7-5, Exercise 2: Choosing projections

Model answer (check the details):

1. A sailing course: Mercator. A line of constant compass bearing is straight, so the course can be plotted and read with a ruler.
2. A map of population density: an equal-area projection, such as Mollweide or Gall-Peters. Density compares people per unit area, so areas must be true to scale, or the colours mislead.
3. A wall map for a school: a compromise projection such as Winkel tripel or Robinson. It keeps the look of the continents reasonable and keeps all the distortions modest, with no one property exact.

Reason in general: the projection is part of the argument of the map, so choose the one whose distortions do least harm to the point being made.