The Salmon Projection: A Four-Disc Surface-and-Section Representation of the Terrestrial Globe

The Salmon Projection is a whole-Earth representation composed of four tangent circular discs arranged two-over-two. A single meridional cut through the centre of the Pacific Ocean (the 160°E–20°W great circle) severs the globe into a Western and an Eastern hemisphere, chosen so that no continental landmass is divided.

The upper pair of discs present each hemisphere projected orthographically and rendered in true surface elevation. The lower pair present the corresponding radial cross-sections of the planet — crust, mantle, outer core and inner core — drawn as concentric offset lines at true proportional depth. Because the Earth is radially symmetric to first order, the two sections are identical. The projection therefore unifies, in a single sheet, the planet's surface and its interior under one consistent scale.

The twin-circle double-hemisphere layout and the Pacific-centred cut are long-established and are not claimed as original. The contribution of this work is the vertical pairing of a true-elevation surface disc with a true-depth section disc for each hemisphere, at a shared radius and scale, forming a single four-disc composition. The precise geometric centre of the core discs is defined herein as the Patterson Point.

Released under CC-BY-4.0. This is a scholarly-style preprint; it is not peer-reviewed and does not constitute a patent filing.