Expand description
§Solar Positioning Library
High-accuracy solar positioning algorithms for calculating sun position and sunrise/sunset times.
This library provides implementations of two complementary solar positioning algorithms:
- SPA (Solar Position Algorithm): NREL’s high-accuracy algorithm (±0.0003°, years -2000 to 6000)
- Grena3: Simplified algorithm (±0.01°, years 2010-2110, ~10x faster)
Supports both std (with chrono) and no_std (with libm) environments.
§References
- Reda, I.; Andreas, A. (2003). Solar position algorithm for solar radiation applications. Solar Energy, 76(5), 577-589. DOI: http://dx.doi.org/10.1016/j.solener.2003.12.003
- Grena, R. (2012). Five new algorithms for the computation of sun position from 2010 to 2110. Solar Energy, 86(5), 1323-1337. DOI: http://dx.doi.org/10.1016/j.solener.2012.01.024
§Features
- Thread-safe, immutable data structures
- Performance optimizations for coordinate sweeps (SPA only)
no_stdsupport withlibmfeature (sunrise/sunset requirestd)
§Quick Start
§Solar Position (with std)
use solar_positioning::{spa, RefractionCorrection, time::DeltaT};
use chrono::{DateTime, FixedOffset};
// Calculate sun position for Vienna at noon
let datetime = "2026-06-21T12:00:00+02:00".parse::<DateTime<FixedOffset>>().unwrap();
let position = spa::solar_position(
datetime,
48.21, // Vienna latitude
16.37, // Vienna longitude
190.0, // elevation (meters)
DeltaT::estimate_from_date_like(datetime).unwrap(), // delta T
Some(RefractionCorrection::standard())
).unwrap();
println!("Azimuth: {:.3}°", position.azimuth());
println!("Elevation: {:.3}°", position.elevation_angle());§Solar Position (no_std mode)
use solar_positioning::{spa, time::JulianDate, RefractionCorrection};
// Create Julian date from components (2026-06-21 12:00:00 UTC)
let jd = JulianDate::from_utc(2026, 6, 21, 12, 0, 0.0, 69.0).unwrap();
// Calculate sun position
let position = spa::solar_position_from_julian(
jd,
48.21, // Vienna latitude
16.37, // Vienna longitude
190.0, // elevation (meters)
Some(RefractionCorrection::standard())
).unwrap();
println!("Azimuth: {:.3}°", position.azimuth());
println!("Elevation: {:.3}°", position.elevation_angle());§Sunrise and Sunset (requires std)
use solar_positioning::{spa, Horizon, time::DeltaT};
use chrono::{DateTime, FixedOffset};
// Calculate sunrise/sunset for San Francisco
let date = "2026-06-21T00:00:00-07:00".parse::<DateTime<FixedOffset>>().unwrap();
let result = spa::sunrise_sunset_for_horizon(
date,
37.7749, // San Francisco latitude
-122.4194, // San Francisco longitude
DeltaT::estimate_from_date_like(date).unwrap(),
Horizon::SunriseSunset
).unwrap();
match result {
solar_positioning::SunriseResult::RegularDay { sunrise, transit, sunset } => {
println!("Sunrise: {}", sunrise);
println!("Solar noon: {}", transit);
println!("Sunset: {}", sunset);
}
_ => println!("No sunrise/sunset (polar day/night)"),
}§Algorithms
§SPA (Solar Position Algorithm)
Based on the NREL algorithm by Reda & Andreas (2003). Provides the highest accuracy with uncertainties of ±0.0003 degrees, suitable for applications requiring precise solar positioning over long time periods.
§Grena3
A simplified algorithm optimized for years 2010-2110. Approximately 10 times faster than SPA while maintaining good accuracy (maximum error 0.01°).
§Coordinate System
- Azimuth: 0° = North, measured clockwise (0° to 360°)
- Zenith angle: 0° = directly overhead (zenith), 90° = horizon (0° to 180°)
- Elevation angle: 0° = horizon, 90° = directly overhead (-90° to +90°)
Re-exports§
pub use crate::error::Error;pub use crate::error::Result;pub use crate::spa::spa_time_dependent_parts;pub use crate::spa::SpaTimeDependent;pub use crate::spa::spa_with_time_dependent_parts;pub use crate::types::Horizon;pub use crate::types::RefractionCorrection;pub use crate::types::SolarPosition;pub use crate::types::SunriseResult;