Loxodrome Plugin

The loxodrome is a spiral curve on the surface of a sphere which crosses all meridians of longitude at the same angle. This is the path a ship would follow if it traveled around the earth without changing direction. In other words, if the ship proceeded along a course with constant bearing relative to true north, then it would trace out a loxodrome curve as it circled the globe.

The windings get closer together as they approach each pole. The spiral never actually reaches the pole.

M.C. Escher used this curve for his drawing, Sphere Spirals.

This plugin is accessed from the Draw menu (Draw > Loxodrome). This will open a dialog box to enter the loxodrome parameter values.

The Bearing parameter is the angle in degrees between the spiral curve and a meridian of longitude. In the ship analogy, it is the number of degrees east of north that the ship's course is bearing. The spiral converges very quickly to the poles unless the bearing is close to 90 degrees.

The more edges per revolution, the smoother the curve.

When you click OK, the loxodrome curve is created as a component, and the component placement tool is activated to position the spiral in the model.

The dialog box remembers the values between SketchUp sessions.

The Loxodrome plugin is downloaded as a Ruby zipped (.rbz) file. This SketchUp Help Article has step by step instructions for installing Ruby plugin extensions.