WIP show POI list on click, save to RS

app/utils/geo.js

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+export function getDistance(lat1, lon1, lat2, lon2) {
+  const R = 6371e3; // metres
+  const φ1 = (lat1 * Math.PI) / 180; // φ, λ in radians
+  const φ2 = (lat2 * Math.PI) / 180;
+  const Δφ = ((lat2 - lat1) * Math.PI) / 180;
+  const Δλ = ((lon2 - lon1) * Math.PI) / 180;
+
+  const a =
+    Math.sin(Δφ / 2) * Math.sin(Δφ / 2) +
+    Math.cos(φ1) * Math.cos(φ2) * Math.sin(Δλ / 2) * Math.sin(Δλ / 2);
+  const c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
+
+  return R * c; // in metres
+}