Mapping HeightReference.RELATIVE_TO_GROUND to true height

CesiumJS
1

I am building a drone tracker which updates the drone’s position in realtime. I use “heightReference: HeightReference.RELATIVE_TO_GROUND” on my drone model, to visualise its actual position above ground.

I wish to draw a line which shows a “power output” for a specific coordinate on its flight path. But the flight path appears way below the drone due to “HeightReference.RELATIVE_TO_GROUND”.

Is there a way to get my entity’s actual current position, so i can draw the line corresponding to the drone’s real position?

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i draw the flight path as such:
update(lon: number, lat: number, alt: number, color: Color) {
const newPosition = Cartesian3.fromDegrees(lon, lat, alt);

    // Add the new position and color to the arrays
    this.positions.push(newPosition);
    this.colors.push(color);

    // If the primitive exists, remove it before creating the updated one
    if (this.primitive) {
        this.viewer.scene.primitives.remove(this.primitive);
    }

    // Create a new primitive with updated geometry
    if (this.positions.length > 1) {
        this.createPrimitive();
    }
}

private createPrimitive() {
if (!this.viewer) {
return
}
const geometry = new PolylineGeometry({
positions: this.positions,
vertexFormat: PolylineColorAppearance.VERTEX_FORMAT,
colors: this.colors,
colorsPerVertex: true,
width: 5
});

    const geometryInstance = new GeometryInstance({
        geometry: geometry,
    });

    this.primitive = new Primitive({
        geometryInstances: geometryInstance,
        appearance: new PolylineColorAppearance(),
        asynchronous: false
    });

    this.viewer.scene.primitives.add(this.primitive);
}

And i give the exact same coordinates when moving the drone as when updating the flight path:
this.moveDrone(lon, lat, alt);
const color = this.getColorForPower(power);
this.flightPath.update(lon, lat, alt, color);

2

Just a quick update to my own post:

What i ended up doing was using Cesium.sampleTerrainMostDetailed for the given longitude and latitude and then adding the resulting height to my altitude, which works!

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