✨ added geo functions

Author: saby1101

src/geo.spec.ts

@@ -0,0 +1,15 @@
+import { haversine, bearing } from "./geo";
+
+test("haversine", () => {
+  const lat1 = 17.408992;
+  const lon1 = 78.490229;
+  const lat2 = 17.41583;
+  const lon2 = 78.498372;
+  expect(haversine(lat1, lon1, lat2, lon2)).toBe(1150.9015135733925);
+});
+
+test("bearing", () => {
+  expect((bearing(52.205, 0.119, 48.857, 2.351) * 180) / Math.PI).toBe(
+    156.16658258153174
+  );
+});

src/geo.ts

@@ -0,0 +1,85 @@
+const { sin, cos, atan2, sqrt, PI } = Math;
+
+const PIBy180 = PI / 180;
+const _180ByPI = 180 / PI;
+
+export const convToRad = (degrees: number) => degrees * PIBy180;
+export const convToDeg = (rads: number) => rads * _180ByPI;
+const sq = (num: number) => num * num;
+
+export const R = 6371e3; // Radius of earth in metres
+
+export const validate = (lat: number, lon: number) => {
+  if (!Number.isFinite(lat)) {
+    return false;
+  }
+  if (!Number.isFinite(lon)) {
+    return false;
+  }
+  if (lat > 90 || lat < -90) {
+    return false;
+  }
+  if (lon > 180 || lon < -180) {
+    return false;
+  }
+  // pathological case. (0, 0) is water
+  if (lon === 0 && lat === 0) {
+    return false;
+  }
+  return true;
+};
+
+export const haversine = (
+  lat1: number,
+  lon1: number,
+  lat2: number,
+  lon2: number
+) => {
+  // in degrees
+  // convert to radians
+  lat1 = convToRad(lat1);
+  lon1 = convToRad(lon1);
+  lat2 = convToRad(lat2);
+  lon2 = convToRad(lon2);
+
+  const dLat = lat2 - lat1;
+  const dLon = lon2 - lon1;
+
+  const a = sq(sin(dLat / 2)) + cos(lat1) * cos(lat2) * sq(sin(dLon / 2));
+
+  const c = 2 * atan2(sqrt(a), sqrt(1 - a));
+
+  return R * c;
+};
+
+export const bearing = (
+  lat1: number,
+  lon1: number,
+  lat2: number,
+  lon2: number
+) => {
+  // convert to radians
+  lat1 = convToRad(lat1);
+  lon1 = convToRad(lon1);
+  lat2 = convToRad(lat2);
+  lon2 = convToRad(lon2);
+
+  const dLon = lon2 - lon1;
+  return atan2(
+    sin(dLon) * cos(lat2),
+    cos(lat1) * sin(lat2) - sin(lat1) * cos(lat2) * cos(dLon)
+  );
+};
+
+export const normaliseDegs = (degs: number) => (degs + 360) % 360;
+
+export const bearingInDegs = (
+  lat1: number,
+  lon1: number,
+  lat2: number,
+  lon2: number
+) => {
+  const rads = bearing(lat1, lon1, lat2, lon2);
+  const degs = convToDeg(rads);
+  return normaliseDegs(degs);
+};

src/index.ts

@@ -1,3 +1,4 @@
 export * as Lang from "./lang";
 export * as Graph from "./graph";
 export * as BinPack from "./binpack";
+export * as Geo from "./geo";