Province from Coordinates

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Function

findProvinceFromCoordinate(pointToCheck: {
  longitude: number;
  latitude: number;
}): { fa: string; en: string }

import { findProvinceFromCoordinate } from "@persian-tools/persian-tools";

findProvinceFromCoordinate({ longitude: 51.42, latitude: 35.69 });
// { fa: "تهران", en: "Tehran" }

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Behaviour

1. Iterate the polygons (one per province, from irGeoJSON.ts).
2. Run a horizontal ray-cast point-in-polygon test.
3. Return { fa, en } for the first match.
4. If no polygon contains the point, throw PersianToolsError("findProvinceFromCoordinate", "no province found").

Return type is the object { fa, en } — not a string. Wrap in try/catch for graceful fallback when the coordinate is outside Iran.

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Pitfalls

• Throws on out-of-Iran coordinates.
• Coordinate order is { longitude, latitude } (object form), not the GeoJSON [lng, lat] array.
• The dataset is approximate. Near administrative borders, expect occasional misclassification.
• Don’t expect a bare string — index into .fa or .en.

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Composition

import { findProvinceFromCoordinate, findCapitalByProvince } from "@persian-tools/persian-tools";

const point = { longitude: 51.42, latitude: 35.69 };
const province = findProvinceFromCoordinate(point);
const capital = findCapitalByProvince(province.fa);

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Source