Constant DISTANCE_REGRESSION_FLOOR_NM 

const DISTANCE_REGRESSION_FLOOR_NM: f64 = 0.05;

The absolute floor distance_regressed applies alongside DISTANCE_REGRESSION_RELATIVE, in NM, so a short hop’s own tiny baseline (the two short Gulf of Trieste cases measure a bare 3-4 NM) does not make one percent tighter than floating-point noise can actually promise.