On a plane surface this would be the shortest distance between two points over short distances, where the curvature of the earth is not a major factor, and thus can be used for plotting a vehicle, aircraft or ship's course.
This would be the shortest distance between two points over short distances. This is on a plane surface. This thus can be used for plotting a vehicle. This was on a plane surface. This thus can be used for plotting aircraft. This was on a plane surface. This thus can be used for plotting ship's course. This was on a plane surface. The curvature of the earth is not a major factor.