01 How does waypoint projection (bearing) work – for geodesic/orthodrome and loxodrome/rhumb line?

In general, the waypoint projection (bearing) is based on an original coordinate. By entering the distance and direction, the new target coordinate is calculated according to the selected output format.

However, there is a catch with the projection: in navigation, there are two ways of calculating and displaying the connection between two points:

  • Geodesics or orthodromes
    The start and destination points lie on a great circle. This is the shortest connection between two points.
  • Loxodromes or rhumb lines
    The connection between the starting and destination points always intersects the longitudes/meridians at the same angle.

The earth is not a flat map, but a complicated body that can be described in the best approximation as a flattened sphere, a so-called rotational ellipsoid. A map is a so-called projection of this ellipsoid. This type is called a Mercator projection.

S-Man42 has described this in detail in a blog article.

How does the GC Wizard perform a waypoint projection?