Earth Shape and Stellar Navigation in a Proposed Leo Landscape Alignment in Northern Europe Curvature calibration and the interpretation of a prehistoric route hypothesis

This paper examines whether Earth’s shape, changing stellar views and a traveller’s possible use of flat geometry could explain a discrepancy in a proposed landscape alignment of Leo. The worked example fixes Regulus at a nominal Cologne coordinate and Denebola at Rouen, then derives seven further stations from ratios of stellar angular separations. At the comparison epoch of 3000 BCE, predicted Chertan lies 5.150 km from the retained heritage locator for Sept Bonnettes. Common rotations representing precession or axial orientation preserve the intrinsic angular separations used by this construction. Two planar approximations move Chertan by 5.6–14.4 m; replacing a mean sphere with WGS84 moves it by 91.8 m. An alternative construction using constant-bearing path lengths moves the station by 300.8 m and leaves a 4.850 km gap. A three-station included-angle experiment leaves 5.346 km. Repeated observations at 5 or 10 km intervals do not define a unique route unless the observing and navigation rules are specified. A full 4000 BCE comparison gives a 5.393 km Chertan-to-reference distance. These tests establish conditional geometric results. They do not recover a Neolithic traveller’s cosmology, demonstrate an ancient navigation procedure or date the monument. The remaining discrepancy requires investigation through surveying, independent chronology and predictions at additional sites.