Elevation, horizon, and rise/set calculations
When observer elevation matters and why geometric, standard refracted, and local terrain horizons are different models.
Calculation contract · released 2026-08-18
Definition
Elevation changes the observer position and visible horizon. Atmospheric refraction and terrain obstruction are separate corrections.
Calculation procedure
Record elevation value, unit, vertical reference, refraction model, pressure/temperature assumptions, solar-limb convention, and whether local terrain is modeled.
Required inputs
- WGS 84 horizontal position
- Elevation and vertical datum
- Atmospheric model
- Target body and event definition
Maha convention
Maha’s Pañcāṅga path passes observer elevation to Astronomy Engine and labels missing sunrise or sunset at polar locations instead of fabricating a day fraction.
Uncertainty and edge cases
Refraction and terrain can move observed rise/set times by minutes; a sea-level default should not masquerade as local observational truth.
What this does not establish
A computed standard sunrise is not necessarily the first locally visible light over terrain.
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.
- WGS 84 geographic 2D coordinate reference system
EPSG Geodetic Parameter Registry · EPSG:4326 (revision 2022-11-29)
The WGS 84 latitude and longitude coordinate reference system and axis/unit definitions used for terrestrial observer locations.
Boundary: EPSG:4326 is horizontal; elevation must separately name its value, unit, reference, and uncertainty.