FA-70195 / Map projection transforms / Member archive

Orthographic globe view with back-side culling: northing sign term · case 05

Latitude lines bow the wrong way on a tilted globe.

Member previewVariant 5 · 3 implementations · 8 checks per implementation

Case contract

Input [lon, lat, lon0, lat0] degrees; sphere R = 6371000 viewed from infinity above (lon0, lat0). cos c = sin(p0)sin(p) + cos(p0)cos(p)cos(dl); points with cos c < 0 are on the far side and return None. Otherwise x = R cos(p) sin(dl), y = R (cos(p0) sin(p) - sin(p0) cos(p) cos(dl)), rounded to 2 decimals.

Why this case matters

Globe widgets and inset locator maps draw only the visible hemisphere; wrong culling shows features through the planet.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
control #14	`[-4206814.33, -72311.41]`	`[-4206814.33, 3130521.2]`	Failed

MEMBER ARCHIVE

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This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

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