Surfaces of Gaussian Curvature Zero - Map Projections: Cartographic Information Systems - page 181

Fig. 4.6. Tangent developable of a helix (“developable helix”)
Fig. 4.7. Gauss flat surface ( k = 0) which is not a ruled surface
In the following chapter, focussing on the polar aspect, we study the mapping of the sphere to
a tangential plane.