Numerical precision, rounding, and uncertainty
How Maha prevents printed digits from being mistaken for measurement or model certainty.
Calculation contract · released 2026-08-18
Definition
Precision describes representation; uncertainty bounds plausible error from inputs, models, data, and transformations. They are not interchangeable.
Calculation procedure
Calculate at full internal precision, propagate known input/model envelopes, classify boundary sensitivity, and round only for display while retaining the original value.
Required inputs
- Unrounded computed value
- Input uncertainty
- Reference-engine disagreement envelope
- Display precision policy
Maha convention
Maha’s frozen corpus publishes maximum differences and fails CI outside declared release envelopes instead of tuning printed values to agreement.
Uncertainty and edge cases
A value printed to six decimals may still have an uncertainty larger than its final digits; boundary labels should be withheld or flagged accordingly.
What this does not establish
More decimal places do not imply better source evidence or predictive performance.
Authoritative references
These sources establish the calculation vocabulary, data product, or transformation convention. They do not establish astrological interpretation.
- Horizons System Manual
NASA/JPL Solar System Dynamics · 4.98d (2025-11-21)
Solar-system object identifiers, observing centers, time inputs, reference frames, corrections, output quantities, and stated ephemeris limitations.
Boundary: Horizons output is authoritative only with the complete query contract preserved; transformed or rounded values require their own provenance record.
- 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.