Terrain Min-Max Height Extraction

The following example shows how to extract min/max terrain height value from a terrain provider at a selected area, area is defined by a bounding polygon.

info

In order to set a terrain provider, see here.

Cesium

info

The minimum required version for cesium is v84.

const polygon = turf.polygon([
  [
    [-72.37353086471558, 42.32481709325035],
    [-72.3738956451416, 42.324594989789134],
    [-72.3735523223877, 42.324436343979656],
    [-72.37387418746948, 42.32430942704402],
    [-72.37363815307616, 42.32405559240466],
    [-72.37391710281372, 42.32388108049599],
    [-72.37363815307616, 42.32367483852534],
    [-72.37352013587952, 42.32375416244021],
    [-72.37370252609253, 42.32385728338004],
    [-72.37343430519104, 42.32408732179058],
    [-72.37361669540404, 42.32429356240905],
    [-72.37331628799438, 42.324428411678674],
    [-72.373605966568, 42.3246108543481],
    [-72.37338066101074, 42.32473777067564],
    [-72.37353086471558, 42.32481709325035]
  ]
]);

// Takes a set of features, calculates the bbox of all input features
// and returns a bounding box
const bbox = turf.bbox(polygon); // bbox extent in minX, minY, maxX, maxY order
const cellSide = 1.0; // distance between points (in units)
const options = {
  units: 'meters', // used in calculating cellSide, can be: degrees, radians, miles, or kilometers (default)
  mask: polygon // if passed a Polygon or MultiPolygon, the grid Points will be created only inside it
};

// Creates a Point grid from a bounding box, FeatureCollection or Feature.
const pointGrid = turf.pointGrid(bbox, cellSide, options); // grid of points
const pointGridCoordinates = pointGrid.features.map(f => f.geometry.coordinates);

console.log(pointGridCoordinates); // 2,359 points inside the polygon

pointGridCoordinates.forEach(p => {
  viewer.entities.add({
    position: Cesium.Cartesian3.fromDegrees(p[0], p[1]),
    point: {
      color: Cesium.Color.fromRandom(),
      pixelSize: 5,
      heightReference: Cesium.HeightReference.RELATIVE_TO_GROUND
    }
  });
});
const positions = pointGridCoordinates.map(p => Cesium.Cartographic.fromDegrees(p[0], p[1]));
void Cesium.sampleTerrainMostDetailed(
  viewer.terrainProvider,
  positions
).then((updatedPositions) => {
  // Calculate which coordinate has min/max height
  ...
});

caution

Above example is based on Pseudo code, you will have to adapt it in your own application to make it work. Please note:
Time increases with the amount of sampling points.
Number of requests does not change however due to sampling points density which happen to correspond with the same tiles.
This example was tested against Cesium World Terrain over the internet.
Need to consider amount of sampling points against the resolution of the source height product.

Distance between points(cellSide)	Number of Sampling Points	Number of Requests	Time to Sample (seconds)
30.0	1	1	0.53
20.0	7	4	0.56
15.0	9	2	0.59
1.0	2,359	4	0.98
0.5	9,427	4	1.15
0.4	14,748	4	1.35
0.3	26,225	4	1.59
0.2	58,891	4	2.88

Terrain Min-Max Height Extraction​

Cesium​

Terrain Min-Max Height Extraction

Cesium