mirror of
https://github.com/acamarata/pray-calc-ml.git
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bbe1bf5cbc
Weighted least-squares calibration of Islamic prayer time depression angles from observed mosque announcement data. Uses golden-section search to minimize the sum of squared residuals independently for Fajr and Isha. Internal Jean Meeus solar ephemeris — zero runtime dependencies. API: calibrateAngles, scoreAngles, predictFajr, predictIsha. Full TypeScript, dual CJS/ESM via tsup. 32 ESM tests, 6 CJS tests, all passing on Node 20/22/24.
43 lines
1.3 KiB
TypeScript
43 lines
1.3 KiB
TypeScript
/**
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* Predict Fajr and Isha times given depression angles.
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*
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* Uses the internal solar module to avoid requiring pray-calc at calibration time.
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* Accuracy matches pray-calc within ~0.5 min for most locations (no atmospheric
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* refraction correction here — the calibration absorbs that into the fitted angle).
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*/
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import { jdn, horizonCrossing } from './solar.js';
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/**
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* Predict Fajr time (fractional hours, local) for a given depression angle.
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* Returns NaN if the sun never reaches that depth below the horizon.
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*/
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export function predictFajr(
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date: Date,
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lat: number,
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lng: number,
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tz: number,
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fajrAngle: number,
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): number {
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const jd = jdn(new Date(Date.UTC(date.getFullYear(), date.getMonth(), date.getDate(), 12)));
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const altDeg = -(fajrAngle); // depression → negative altitude
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const [rise] = horizonCrossing(jd, lat, lng, tz, altDeg);
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return rise;
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}
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/**
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* Predict Isha time (fractional hours, local) for a given depression angle.
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* Returns NaN if the sun never reaches that depth below the horizon.
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*/
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export function predictIsha(
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date: Date,
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lat: number,
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lng: number,
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tz: number,
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ishaAngle: number,
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): number {
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const jd = jdn(new Date(Date.UTC(date.getFullYear(), date.getMonth(), date.getDate(), 12)));
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const altDeg = -(ishaAngle);
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const [, set] = horizonCrossing(jd, lat, lng, tz, altDeg);
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return set;
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}
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