diff --git a/conversions/navigationdata.js b/conversions/navigationdata.js
index f066fd5..51a11e0 100644
--- a/conversions/navigationdata.js
+++ b/conversions/navigationdata.js
@@ -26,7 +26,8 @@ module.exports = (app, plugin) => {
         }
       }]
     }]
-  }, {
+  }, 
+  {
     pgn: 129284,
     title: 'Navigation Data (129284)',
     optionKey: 'navigationdata',
@@ -98,5 +99,79 @@ module.exports = (app, plugin) => {
         }
       }]
     }]
-  }]
+  },
+  {
+    pgn: 129284,
+    title: 'Navigation Data Great Circle (129284)',
+    optionKey: 'navigationdatagc',
+    keys: [
+      'navigation.courseGreatCircle.nextPoint.distance',
+      'navigation.courseGreatCircle.bearingToDestinationTrue',
+      'navigation.courseGreatCircle.bearingOriginToDestinationTrue',
+      'navigation.courseGreatCircle.nextPoint',
+      'navigation.courseGreatCircle.nextPoint.velocityMadeGood',
+      'notifications.arrivalCircleEntered',
+      'notifications.perpendicularPassed',
+      'navigation.courseGreatCircle.nextPoint.ID'
+    ],
+    timeouts: [
+      10000, 10000, 10000, 10000, 10000, undefined, undefined, 10000
+    ],
+    callback: (distToDest, bearingToDest, bearingOriginToDest, dest, WCV, ace, pp, wpid) => {
+      var dateObj = new Date();
+      var secondsToGo = Math.trunc(distToDest / WCV);
+      var etaDate = Math.trunc((dateObj.getTime() / 1000 + secondsToGo) / 86400);
+      var etaTime = (dateObj.getUTCHours() * (60 * 60) +
+                     dateObj.getUTCMinutes() * 60 +
+                     dateObj.getUTCSeconds() +
+                     secondsToGo) % 86400;
+
+      return [{
+        pgn: 129284,
+        "SID" : 0x88,
+        "Distance to Waypoint" :  distToDest,
+        "Course/Bearing reference" : 0,
+        "Perpendicular Crossed" : pp != null,
+        "Arrival Circle Entered" : ace != null,
+        "Calculation Type" : 0,
+        "ETA Time" : (WCV > 0) ? etaTime : undefined,
+        "ETA Date": (WCV > 0) ? etaDate : undefined,
+        "Bearing, Origin to Destination Waypoint" : bearingOriginToDest,
+        "Bearing, Position to Destination Waypoint" : bearingToDest,
+        "Origin Waypoint Number" : undefined,
+        "Destination Waypoint Number" : parseInt(wpid),
+        "Destination Latitude" : dest.latitude,
+        "Destination Longitude" : dest.longitude,
+        "Waypoint Closing Velocity" : WCV,
+      }]
+    },
+    tests: [{
+      input: [ 12, 1.23, 3.1, { longitude: -75.487264, latitude: 32.0631296 } , 4.0, null, 1, 5 ],
+      expected: [{
+        "__preprocess__": (testResult) => {
+          //these change every time
+          delete testResult.fields["ETA Date"]
+          delete testResult.fields["ETA Time"]
+        },
+        "prio": 2,
+        "pgn": 129284,
+        "dst": 255,
+        "fields": {
+          "SID": 136,
+          "Distance to Waypoint": 12,
+          "Course/Bearing reference": "True",
+          "Perpendicular Crossed": "Yes",
+          "Arrival Circle Entered": "No",
+          "Calculation Type": "Great Circle",
+          "Bearing, Origin to Destination Waypoint": 3.1,
+          "Bearing, Position to Destination Waypoint": 1.23,
+          "Destination Waypoint Number": 5,
+          "Destination Latitude": 32.0631296,
+          "Destination Longitude": -75.487264,
+          "Waypoint Closing Velocity": 4
+        }
+      }]
+    }]
+  }
+]
 }