Which projection has projection rays parallel and perpendicular to a plane tangent to a sphere?

• A. Lambert Conformal Projection
• B. Gnomonic Projection
• C. Stereographic Projection
• D. Orthographic Projection

Answer: (D)

The idea being tested is a parallel, perpendicular projection onto a plane that just touches the sphere. When the projection rays are all parallel to each other and perpendicular to the projection plane, you’re dealing with an orthographic (parallel) projection. If that plane is tangent to the sphere, the rays hit the plane at right angles, giving a clean, non-perspective map of the sphere onto that tangent plane.

The other projections don’t fit this setup because their projection rays aren’t all parallel to a single tangent plane: gnomonic projects from the sphere’s center onto the plane, so the rays radiate outward rather than run parallel; stereographic projects from the opposite point onto the plane, again with rays that aren’t parallel to a single plane; Lambert conformal is typically a conic or cylindrical projection with projection lines arranged relative to a standard surface rather than a single tangent plane to the sphere.