Add queryTerrainElevation

CHANGELOG.md

@@ -1,4 +1,5 @@
 ## main
+- Add queryTerrainElevation allows getting terrain elevation in meters at specific point ([#2264](https://github.com/maplibre/maplibre-gl-js/pull/2264))
 
 - Fix the type of the `features` property on `MapLayerMouseEvent` and `MapLayerTouchEvent` to be `MapGeoJSONFeature[]` in lieu of `GeoJSON.Feature[]` ([#2244](https://github.com/maplibre/maplibre-gl-js/pull/2244))
 

src/ui/camera.test.ts

@@ -6,6 +6,7 @@ import {fixedLngLat, fixedNum} from '../../test/unit/lib/fixed';
 import {setMatchMedia} from '../util/test/util';
 import {mercatorZfromAltitude} from '../geo/mercator_coordinate';
 import Terrain from '../render/terrain';
+import {LngLatLike} from '../geo/lng_lat';
 
 beforeEach(() => {
     setMatchMedia();
@@ -1997,3 +1998,46 @@ describe('#fitScreenCoordinates', () => {
         expect(camera.getBearing()).toBeCloseTo(0);
     });
 });
+
+describe('queryTerrainElevation', () => {
+    let camera: Camera;
+
+    beforeEach(() => {
+        camera = createCamera();
+    });
+
+    test('should return null if terrain is not set', () => {
+        camera.terrain = null;
+        const result = camera.queryTerrainElevation([0, 0]);
+        expect(result).toBeNull();
+    });
+
+    test('should return the correct elevation', () => {
+        // Set up mock transform and terrain objects
+        const transform = new Transform(0, 22, 0, 60, true);
+        transform.getElevation = jest.fn().mockReturnValue(200);
+        transform.elevation = 50;
+        const terrain = {} as Terrain;
+
+        // Set up camera with mock transform and terrain
+        camera.transform = transform;
+        camera.terrain = terrain;
+
+        // Call queryTerrainElevation with mock lngLat
+        const lngLatLike: LngLatLike = [1, 2];
+        const expectedElevation = 150; // 200 - 50 = 150
+        const result = camera.queryTerrainElevation(lngLatLike);
+
+        // Check that transform.getElevation was called with the correct arguments
+        expect(transform.getElevation).toHaveBeenCalledWith(
+            expect.objectContaining({
+                lng: lngLatLike[0],
+                lat: lngLatLike[1],
+            }),
+            terrain
+        );
+
+        // Check that the correct elevation value was returned
+        expect(result).toEqual(expectedElevation);
+    });
+});

src/ui/camera.ts

@@ -1343,6 +1343,26 @@ abstract class Camera extends Evented {
             delta > 180 ? -360 :
                 delta < -180 ? 360 : 0;
     }
+
+    /**
+     * Query the current elevation of location. It return null if terrain is not enabled. the elevation is in meters relative to mean sea-level
+     * @memberof Map#
+     * @param lngLatLike [x,y] or LngLat coordinates of the location
+     * @returns {number} elevation in meters
+     */
+    queryTerrainElevation(lngLatLike: LngLatLike): number | null {
+        if (!this.terrain) {
+            return null;
+        }
+        const elevation = this.transform.getElevation(LngLat.convert(lngLatLike), this.terrain);
+        /**
+         * Different zoomlevels with different terrain-tiles the elvation-values are not the same.
+         * map.transform.elevation variable with the center-altitude.
+         * In maplibre the proj-matrix is translated by this value in negative z-direction.
+         * So we need to add this value to the elevation to get the correct value.
+         */
+        return elevation - this.transform.elevation;
+    }
 }
 
 // In debug builds, check that camera change events are fired in the correct order.