Starting to implement GPX visualization.

src/lib/geo.ts

@@ -1,4 +1,4 @@
-
+import { Rectangle } from '../components/map/types';
 
 // cf https://wiki.openstreetmap.org/wiki/Slippy_map_tilenames#ECMAScript_(JavaScript/ActionScript,_etc.)
 export const lon2tile = (lon: number, zoom: number) => {
@@ -25,3 +25,11 @@ export function tile2lat(y: number, z: number) {
   var n = Math.PI - (2 * Math.PI * y) / Math.pow(2, z);
   return (180 / Math.PI) * Math.atan(0.5 * (Math.exp(n) - Math.exp(-n)));
 }
+
+export const rectanglesIntersect = (r1: Rectangle, r2: Rectangle) =>
+  !(
+    r2.topLeft.x > r1.bottomRight.x ||
+    r2.bottomRight.x < r1.topLeft.x ||
+    r2.topLeft.y > r1.bottomRight.y ||
+    r2.bottomRight.y < r1.topLeft.y
+  );