Update / Consolidate course data calculations (#62)

* Add DTG calculation

* Add geodesy library

* Add XTE calculation

* fix typo

* Add geodesy library

* Add XTE calculation

* create `courseData.js` to hold course calculations

* consolidate DTG calc

* Update VMG calc `group` value

calcs/courseData.js

@@ -0,0 +1,73 @@
+const LatLon = module.require('@panaaj/sk-geodesy/latlon-spherical')
+  .LatLonSpherical
+
+module.exports = function (app) {
+  return {
+    group: 'course data',
+    optionKey: 'dtg',
+    title:
+      'Course DTG, XTE, BRG, etc (based on courseGreatCircle.nextPoint / previousPoint)',
+    derivedFrom: [
+      'navigation.courseGreatCircle.nextPoint.position',
+      'navigation.courseGreatCircle.previousPoint.position',
+      'navigation.position'
+    ],
+    calculator: function (
+      nextPointPosition,
+      previousPointPosition,
+      vesselPosition
+    ) {
+      let pos = vesselPosition
+        ? new LatLon(vesselPosition.latitude, vesselPosition.longitude)
+        : null
+
+      let pathStart = previousPointPosition
+        ? new LatLon(
+          previousPointPosition.latitude,
+          previousPointPosition.longitude
+        )
+        : null
+
+      let pathEnd = nextPointPosition
+        ? new LatLon(nextPointPosition.latitude, nextPointPosition.longitude)
+        : null
+
+      // ** Cross track Error **
+      let xte =
+        !pos || !pathStart || !pathEnd
+          ? null
+          : pos.crossTrackDistanceTo(pathStart, pathEnd)
+
+      // The bearing of a line between previousPoint and nextPoint, relative to true north.
+      let trkBearingTrue =
+        !pos || !pathStart || !pathEnd
+          ? null
+          : pathStart.initialBearingTo(pathEnd)
+
+      // ** Distance from vessel to nextPoint **
+      let dtg = !pos || !pathEnd ? null : pos.distanceTo(pathEnd)
+
+      // The bearing of a line between the vessel's current position and nextPoint, relative to true north
+      let brg = !pos || !pathEnd ? null : pos.initialBearingTo(pathEnd)
+
+      return [
+        {
+          path: 'navigation.courseGreatCircle.crossTrackError',
+          value: xte
+        },
+        {
+          path: 'navigation.courseGreatCircle.bearingTrackTrue',
+          value: trkBearingTrue
+        },
+        {
+          path: 'navigation.courseGreatCircle.nextPoint.distance',
+          value: dtg
+        },
+        {
+          path: 'navigation.courseGreatCircle.nextPoint.bearingTrue',
+          value: brg
+        }
+      ]
+    }
+  }
+}

calcs/vmg.js

@@ -1,6 +1,6 @@
 module.exports = function (app) {
   return {
-    group: 'vmg',
+    group: 'course data',
     optionKey: 'vmg_Course',
     title:
       'Velocity Made Good to Course (based on courseGreatCircle.nextPoint.bearingTrue heading true and speedOverGround)',

calcs/vmg_wind.js

@@ -1,6 +1,6 @@
 module.exports = function (app) {
   return {
-    group: 'vmg',
+    group: 'course data',
     optionKey: 'vmg_Wind',
     title:
       'Velocity Made Good to wind (based on wind.directionTrue and speedOverGround)',

package.json

@@ -36,6 +36,7 @@
     }
   },
   "dependencies": {
+    "@panaaj/sk-geodesy": "^1.0.0",
     "baconjs": "^0.7.88",
     "cubic-spline": "^1.0.4",
     "geolib": "^2.0.24",