geodesy - npm Package Compare versions

Comparing version 2.3.0 to 2.4.0

latlon-ellipsoidal-vincenty.js

 /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
-/* Vincenty Direct and Inverse Solution of Geodesics on the Ellipsoid (c) Chris Veness 2002-2021  */
+/* Vincenty Direct and Inverse Solution of Geodesics on the Ellipsoid (c) Chris Veness 2002-2022  */
 /*                                                                                   MIT Licence  */
@@ -226,3 +226,3 @@ /* www.movable-type.co.uk/scripts/latlong-vincenty.html                                           */
             σ = s / (b*A) + Δσ;
-        } while (Math.abs(σ-σʹ) > 1e-12 && ++iterations<100);
+        } while (Math.abs(σ-σʹ) > 1e-12 && ++iterations<100); // TV: 'iterate until negligible change in λ' (≈0.006mm)
         if (iterations >= 100) throw new EvalError('Vincenty formula failed to converge'); // not possible?
@@ -289,3 +289,3 @@
             sinSqσ = (cosU2*sinλ)**2 + (cosU1*sinU2-sinU1*cosU2*cosλ)**2;
-            if (Math.abs(sinSqσ) < ε) break;  // co-incident/antipodal points (falls back on λ/σ = L)
+            if (Math.abs(sinSqσ) < 1e-24) break;  // co-incident/antipodal points (σ < ≈0.006mm)
             sinσ = Math.sqrt(sinSqσ);
@@ -302,3 +302,3 @@ cosσ = sinU1*sinU2 + cosU1*cosU2*cosλ;
             if (iterationCheck > π) throw new EvalError('λ > π');
-        } while (Math.abs(λ-λʹ) > 1e-12 && ++iterations<1000);
+        } while (Math.abs(λ-λʹ) > 1e-12 && ++iterations<1000); // TV: 'iterate until negligible change in λ' (≈0.006mm)
         if (iterations >= 1000) throw new EvalError('Vincenty formula failed to converge');
@@ -305,0 +305,0 @@

latlon-ellipsoidal.js

 /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
-/* Geodesy tools for an ellipsoidal earth model                       (c) Chris Veness 2005-2019  */
+/* Geodesy tools for an ellipsoidal earth model                       (c) Chris Veness 2005-2022  */
 /*                                                                                   MIT Licence  */
+/* Core class for latlon-ellipsoidal-datum & latlon-ellipsoidal-referenceframe.                   */
+/*                                                                                                */
 /* www.movable-type.co.uk/scripts/latlong-convert-coords.html                                     */
@@ -80,5 +82,5 @@ /* www.movable-type.co.uk/scripts/geodesy-library.html#latlon-ellipsoidal                         */
     constructor(lat, lon, height=0) {
-        if (isNaN(lat)) throw new TypeError(`invalid lat ‘${lat}’`);
-        if (isNaN(lon)) throw new TypeError(`invalid lon ‘${lon}’`);
-        if (isNaN(height)) throw new TypeError(`invalid height ‘${height}’`);
+        if (isNaN(lat) || lat == null) throw new TypeError(`invalid lat ‘${lat}’`);
+        if (isNaN(lon) || lon == null) throw new TypeError(`invalid lon ‘${lon}’`);
+        if (isNaN(height) || height == null) throw new TypeError(`invalid height ‘${height}’`);
 
@@ -85,0 +87,0 @@ this._lat = Dms.wrap90(Number(lat));

latlon-nvector-spherical.js

 /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
-/* Vector-based spherical geodetic (latitude/longitude) functions     (c) Chris Veness 2011-2021  */
+/* Vector-based spherical geodetic (latitude/longitude) functions     (c) Chris Veness 2011-2022  */
 /*                                                                                   MIT Licence  */
@@ -543,3 +543,3 @@ /* www.movable-type.co.uk/scripts/latlong-vectors.html                                            */
      * @param   {LatLon} point2 - End point of great circle segment.
-     * @returns {LatLon} point on segment.
+     * @returns {LatLon} Closest point on segment.
      *
@@ -718,8 +718,4 @@ * @example
 
-        // close the polygon so that the last point equals the first point
-        const closed = polygon[0].equals(polygon[polygon.length-1]);
-        if (!closed) polygon.push(polygon[0]);
+        const nVertices = polygon.length;
 
-        const nVertices = polygon.length - 1;
-
         const p = this.toNvector();
@@ -738,4 +734,2 @@
 
-        if (!closed) polygon.pop(); // restore polygon to pristine condition
-
         return Math.abs(Σθ) > π;
@@ -762,17 +756,12 @@ }
 
-        // close the polygon so that the last point equals the first point
-        const closed = polygon[0].equals(polygon[polygon.length-1]);
-        if (!closed) polygon.push(polygon[0]);
-
-        const n = polygon.length - 1; // number of vertices
-
-        // get great-circle vector for each segment
+        // get great-circle vector representing each segment
         const c = [];
-        for (let v=0; v<n; v++) {
+        for (let v=0; v<polygon.length; v++) {
+            if (polygon[v].equals(polygon[(v+1) % polygon.length])) continue; // ignore final vertex of closed polygon
             const i = polygon[v].toNvector();
-            const j = polygon[v+1].toNvector();
-            c[v] = i.cross(j); // great circle for segment v..v+1
+            const j = polygon[(v+1) % polygon.length].toNvector();
+            c.push(i.cross(j)); // great circle for segment v..v+1
         }
-        c.push(c[0]);
 
+        const n = c.length; // number of segments (≡ distinct vertices)
         // sum interior angles; depending on whether polygon is cw or ccw, angle between edges is
@@ -784,3 +773,3 @@ // π−α or π+α, where α is angle between great-circle vectors; so sum α, then take n·π − |Σα|
         let Σα = 0;
-        for (let v=0; v<n; v++) Σα += c[v].angleTo(c[v+1], n1);
+        for (let v=0; v<n; v++) Σα += c[v].angleTo(c[(v+1) % n], n1);
         const Σθ = n*π - Math.abs(Σα);
@@ -792,7 +781,5 @@
 
-        const E = (Σθ - (n-2)*π); // spherical excess (in steradians)
-        const A = E * R*R;        // area in units of R²
+        const E = Σθ - (n-2)*π; // spherical excess (in steradians)
+        const A = E * R*R;      // area (in units of R²)
 
-        if (!closed) polygon.pop(); // restore polygon to pristine condition
-
         return A;
@@ -803,2 +790,36 @@ }
     /**
+     * Calculates the centre of a spherical polygon where the sides of the polygon are great circle
+     * arcs joining the vertices.
+     *
+     * Based on a ‘non-obvious application of Stokes’ theorem’ giving C = Σ[a×b / |a×b| ⋅ θab/2] for
+     * each pair of consecutive vertices a, b; stackoverflow.com/questions/19897187#answer-38201499.
+     *
+     * @param   {LatLon[]} polygon - Array of points defining vertices of the polygon.
+     * @returns {LatLon}   Centre point of the polygon.
+     *
+     * @example
+     *   const polygon = [ new LatLon(0, 0), new LatLon(1, 0), new LatLon(1, 1), new LatLon(0, 1) ];
+     *   const centre = LatLon.centreOf(polygon); // 0.500°N, 0.500°E
+     */
+    static centreOf(polygon) {
+        let centreV = new NvectorSpherical(0, 0, 0);
+        for (let vertex=0; vertex<polygon.length; vertex++) {
+            const a = polygon[vertex].toNvector();                      // current vertex
+            const b = polygon[(vertex+1) % polygon.length].toNvector(); // next vertex
+            const v = a.cross(b).unit().times(a.angleTo(b)/2);          // a×b / |a×b| ⋅ θab/2
+            centreV = centreV.plus(v);
+        }
+
+        // if centreV is pointing in opposite direction to 1st vertex (depending on cw/ccw), negate it
+        const θ = centreV.angleTo(polygon[0].toNvector());
+        if (θ > π/2) centreV = centreV.negate();
+
+        const centreP = new NvectorSpherical(centreV.x, centreV.y, centreV.z).toLatLon();
+
+        return centreP;
+    }
+    static centerOf(polygon) { return LatLonNvectorSpherical.centreOf(polygon); } // for en-us American English
+
+
+    /**
      * Returns point representing geographic mean of supplied points.
@@ -805,0 +826,0 @@ *

package.json

@@ -11,3 +11,3 @@ {
   "author": "Chris Veness",
-  "version": "2.3.0",
+  "version": "2.4.0",
   "license": "MIT",
@@ -14,0 +14,0 @@ "type": "module",

README.md

@@ -99,3 +99,3 @@ Geodesy functions
 <script type="module">
-    import LatLon from 'https://cdn.jsdelivr.net/npm/geodesy@2.3.0/latlon-spherical.min.js';
+    import LatLon from 'https://cdn.jsdelivr.net/npm/geodesy@2.4.0/latlon-spherical.min.js';
 
@@ -132,11 +132,13 @@ const p1 = new LatLon(50.06632, -5.71475);
 
-    import LatLon  from 'geodesy/latlon-nvector-ellipsoidal.js';
-    import LatLonV from 'geodesy/latlon-ellipsoidal-vincenty.js';
+```javascript
+import LatLon  from 'geodesy/latlon-nvector-ellipsoidal.js';
+import LatLonV from 'geodesy/latlon-ellipsoidal-vincenty.js';
 
-    for (const method of Object.getOwnPropertyNames(LatLonV.prototype)) {
-        LatLon.prototype[method] = LatLonV.prototype[method];
-    }
+for (const method of Object.getOwnPropertyNames(LatLonV.prototype)) {
+    LatLon.prototype[method] = LatLonV.prototype[method];
+}
 
-    const d = new LatLon(51, 0).distanceTo(new LatLon(52, 1));
-    const δ = new LatLon(51, 0).deltaTo(new LatLon(52, 1));
+const d = new LatLon(51, 0).distanceTo(new LatLon(52, 1)); // vincenty
+const δ = new LatLon(51, 0).deltaTo(new LatLon(52, 1));    // n-vector
+```
 
@@ -143,0 +145,0 @@ More care is of course required if there are conflicting constructors or method names.

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Total package byte prevSize

271025

increased by0.61%

Lines of code

4779

increased by0.48%

Number of lines in readme file

239

increased by0.84%

No dependency changes