The chart geometry is astronomical
Positions, observer location, horizon coordinates, and ephemerides are astronomical quantities. Systems such as JPL Horizons generate object positions and observability as functions of time and observer location.
Sources: NASA/JPL — Horizons System Manual · U.S. Naval Observatory — Computing Altitude and Azimuth
Meaning can still be personal
A birth, wedding, move, or memorial date can matter because a person says it matters. No astrological claim is required for the sky at that moment to be worth reconstructing.
Interpretation should not masquerade as measurement
Spatial Press keeps calculated geometry, historical source claims, and symbolic interpretation conceptually distinct. That makes it easier to see what was measured or computed and what was later read into the pattern.