Get ground altitude CesiumJS

Question

Is there any way to get ground altitude for a given position in CesiumJS? I tried scene.globe.getHeight func but it returns undefined.

    //marker is a point on map.
var marker = {latitude: 61.08658108795938, longitude: -99.64592791446208};
var height = scene.globe.getHeight( new Cesium.Cartographic(marker.longitude, marker.latitude ) );//undefined

Thank you.

Answer 1

You should use sampleTerrain for this. Here's an example:

// Construct the default list of terrain sources.
var terrainModels = Cesium.createDefaultTerrainProviderViewModels();

// Construct the viewer, with a high-res terrain source pre-selected.
var viewer = new Cesium.Viewer('cesiumContainer', {
    terrainProviderViewModels: terrainModels,
    selectedTerrainProviderViewModel: terrainModels[1]  // Select STK High-res terrain
});

// Get a reference to the ellipsoid, with terrain on it.  (This API may change soon)
var ellipsoid = viewer.scene.globe.ellipsoid;

// Specify our point of interest.
var pointOfInterest = Cesium.Cartographic.fromDegrees(
    -99.64592791446208, 61.08658108795938, 5000, new Cesium.Cartographic());

// [OPTIONAL] Fly the camera there, to see if we got the right point.
viewer.camera.flyTo({
    destination: ellipsoid.cartographicToCartesian(pointOfInterest,
        new Cesium.Cartesian3())
});

// Sample the terrain (async) and write the answer to the console.
Cesium.sampleTerrain(viewer.terrainProvider, 9, [pointOfInterest])
.then(function(samples) {
    console.log('Height in meters is: ' + samples[0].height);
});

Answer 2

This is the alternative:

var marker = new Cesium.Cartesian3.fromDegrees(lon, lat, 0);
markers.push(marker);

var cartographicPositions =
  Cesium.Ellipsoid.WGS84.cartesianArrayToCartographicArray(markers);

var HeightCheck = setInterval(function () {
  if (cesiumTerrainProviderHeightmaps.ready) {
    clearInterval(HeightCheck);

    var promise = Cesium.sampleTerrain(
      cesiumTerrainProviderHeightmaps,
      11,
      cartographicPositions
    );
    Cesium.when(promise, function (cartographicPositions) {
      // you got the altitudes
    });
  } else {
    // "Waiting for height data of terrain...."
  }
}, 1000);