Three methods for cesium to obtain the longitude and latitude at the mouse click

1、 Get the longitude and latitude of the point on the ellipsoid （ Points on an ellipsoid ）

let handler = new Cesium.ScreenSpaceEventHandler(viewer.scene.canvas);
handler.setInputAction(function(event) {
    let cartesian = viewer.camera.pickEllipsoid(event.position);
    let cartographic = Cesium.Cartographic.fromCartesian(cartesian);
    let lng = Cesium.Math.toDegrees(cartographic.longitude); //  longitude 
    let lat = Cesium.Math.toDegrees(cartographic.latitude); //  latitude 
    let alt = cartographic.height; //  Height , Ellipsoid height Always equal to 0
    let coordinate = {
        longitude: Number(lng.toFixed(6)),
        latitude: Number(lat.toFixed(6)),
        altitude: Number(alt.toFixed(2))
    };
    console.log(coordinate);
}, Cesium.ScreenSpaceEventType.LEFT_CLICK);

2、 Get the longitude and latitude of the point on the ground surface （ Points on the terrain ）

let handler = new Cesium.ScreenSpaceEventHandler(viewer.scene.canvas);
handler.setInputAction(function(event){
    let ray = viewer.camera.getPickRay(event.position);
    let cartesian = viewer.scene.globe.pick(ray, viewer.scene);
    let cartographic = Cesium.Cartographic.fromCartesian(cartesian);
    let lng = Cesium.Math.toDegrees(cartographic.longitude); //  longitude 
    let lat = Cesium.Math.toDegrees(cartographic.latitude); //  latitude 
    let alt = cartographic.height; //  Height 
    let coordinate = {
        longitude: Number(lng.toFixed(6)),
        latitude: Number(lat.toFixed(6)),
        altitude: Number(alt.toFixed(2))
    };
    console.log(coordinate);
}, Cesium.ScreenSpaceEventType.LEFT_CLICK);

3、 Get the longitude and latitude of the points in the scene （ Point on Model ）

let handler = new Cesium.ScreenSpaceEventHandler(viewer.scene.canvas);
handler.setInputAction(function (event) {
    let cartesian = viewer.scene.pickPosition(event.position);
    let cartographic = Cesium.Cartographic.fromCartesian(cartesian);
    let lng = Cesium.Math.toDegrees(cartographic.longitude); //  longitude 
    let lat = Cesium.Math.toDegrees(cartographic.latitude); //  latitude 
    let alt = cartographic.height; //  Height 
    let coordinate = {
        longitude: Number(lng.toFixed(6)),
        latitude: Number(lat.toFixed(6)),
        altitude: Number(alt.toFixed(2))
    };
    console.log(coordinate);
}, Cesium.ScreenSpaceEventType.LEFT_CLICK);