Zodiac sign boundary sensitivity
When a sign label should be marked unstable because model or input uncertainty overlaps a 30° boundary.
Calculation contract · released 2026-08-18
Definition
A sign is a floor-based classification of normalized longitude into twelve 30° intervals; the continuous longitude is the underlying calculated fact.
Calculation procedure
Measure angular distance to the nearest 30° boundary, combine relevant uncertainty envelopes, and flag or withhold the sign when the envelope crosses that boundary.
Required inputs
- Unrounded longitude
- Coordinate frame
- Combined angular uncertainty
- Boundary inclusion policy
Maha convention
Maha treats exact-boundary labels in the conformance corpus as non-normative and compares continuous geometry instead.
Uncertainty and edge cases
Rounding before classification can move 29°59′59.9″ to 0° of the next sign even when the stored value remains below the boundary.
What this does not establish
A stable sign classification does not make its interpretation empirically supported.
Authoritative references
These sources establish the calculation vocabulary, data product, or transformation convention. They do not establish astrological interpretation.
- Astronomy Engine
Don Cross (cosinekitty) · 2.1.19
Locally computed Sun and Moon positions derived from the VSOP87 and JPL-derived lunar theories, together with rise and set times, at the accuracy stated in the library documentation.
Boundary: Positions are computed in process rather than fetched from an authority, so a fact citing this source carries a digest over the computed values and not over a provider response body. Its accuracy is adequate for calendrical work and is not a substitute for a Horizons query where sub-arcsecond agreement matters.
- Swiss Ephemeris general documentation
Astrodienst AG · 2.10 documentation, checked 2026-08-18
An independent ephemeris implementation, supported reference choices, house calculations, and its dual-license boundary.
Boundary: Maha does not bundle or call Swiss Ephemeris in production. Frozen conformance results are validation evidence, not permission to redistribute its software or data.
Related calculation contracts
Used by the answer graph
Questions that depend on this contract
2 bounded answers