First version of Karten App

src/adapters/standort.ts

@@ -0,0 +1,33 @@
+import proj4 from "proj4";
+import type { Point } from "../karte/types";
+
+const ETRS25832 =
+  "+proj=utm +zone=32 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs +type=crs";
+
+proj4.defs("EPSG:25832", ETRS25832);
+
+export function toEtrs(lon: number, lat: number): Point {
+  const projected = proj4("EPSG:4326", "EPSG:25832", [lon, lat]);
+  return { easting: projected[0], northing: projected[1] };
+}
+
+export function watchStandort(
+  onStandort: (standort: Point | "denied") => void,
+): () => void {
+  if (!navigator.geolocation) {
+    onStandort("denied");
+    return () => {};
+  }
+
+  const id = navigator.geolocation.watchPosition(
+    (position) => {
+      onStandort(toEtrs(position.coords.longitude, position.coords.latitude));
+    },
+    (error) => {
+      if (error.code === error.PERMISSION_DENIED) onStandort("denied");
+    },
+    { enableHighAccuracy: true },
+  );
+
+  return () => navigator.geolocation.clearWatch(id);
+}