add new anchors by clicking on the temporary one

gpx/src/simplify.ts

@@ -101,4 +101,55 @@ function bearing(latA: number, lonA: number, latB: number, lonB: number): number
     // Finds the bearing from one lat / lon point to another.
     return Math.atan2(Math.sin(lonB - lonA) * Math.cos(latB),
         Math.cos(latA) * Math.sin(latB) - Math.sin(latA) * Math.cos(latB) * Math.cos(lonB - lonA));
+}
+
+export function projectedPoint(point1: TrackPoint, point2: TrackPoint, point3: TrackPoint | Coordinates): Coordinates {
+    return projected(point1.getCoordinates(), point2.getCoordinates(), point3 instanceof TrackPoint ? point3.getCoordinates() : point3);
+}
+
+function projected(coord1: Coordinates, coord2: Coordinates, coord3: Coordinates): Coordinates {
+    // Calculates the point on the line defined by p1 and p2
+    // that is closest to the third point, p3.
+    // Input lat1,lon1,lat2,lon2,lat3,lon3 in degrees.
+
+    const rad = Math.PI / 180;
+    const lat1 = coord1.lat * rad;
+    const lat2 = coord2.lat * rad;
+    const lat3 = coord3.lat * rad;
+
+    const lon1 = coord1.lon * rad;
+    const lon2 = coord2.lon * rad;
+    const lon3 = coord3.lon * rad;
+
+    // Prerequisites for the formulas
+    const bear12 = bearing(lat1, lon1, lat2, lon2);
+    const bear13 = bearing(lat1, lon1, lat3, lon3);
+    let dis13 = distance(lat1, lon1, lat3, lon3);
+
+    let diff = Math.abs(bear13 - bear12);
+    if (diff > Math.PI) {
+        diff = 2 * Math.PI - diff;
+    }
+
+    // Is relative bearing obtuse?
+    if (diff > (Math.PI / 2)) {
+        return coord1;
+    }
+
+    // Find the cross-track distance.
+    let dxt = Math.asin(Math.sin(dis13 / earthRadius) * Math.sin(bear13 - bear12)) * earthRadius;
+
+    // Is p4 beyond the arc?
+    let dis12 = distance(lat1, lon1, lat2, lon2);
+    let dis14 = Math.acos(Math.cos(dis13 / earthRadius) / Math.cos(dxt / earthRadius)) * earthRadius;
+    if (dis14 > dis12) {
+        return coord2;
+    } else {
+        // Determine the closest point (p4) on the great circle
+        const f = dis14 / earthRadius;
+        const lat4 = Math.asin(Math.sin(lat1) * Math.cos(f) + Math.cos(lat1) * Math.sin(f) * Math.cos(bear12));
+        const lon4 = lon1 + Math.atan2(Math.sin(bear12) * Math.sin(f) * Math.cos(lat1), Math.cos(f) - Math.sin(lat1) * Math.sin(lat4));
+
+        return { lat: lat4 / rad, lon: lon4 / rad };
+    }
 }