public override Task <ElevationTile> GetElevationTileData(TileId tileId, CancellationToken cancellationToken = default)
{
if (!_tiles.Contains(tileId))
{
return(ElevationTile.FromNull());
}
// Read the elevation data from the corresponding file in streaming assets. Files are named by the TileId's quadkey.
var elevationTileData = File.ReadAllBytes(Path.Combine(ElevationDataDirectory, tileId.ToKey() + ".et"));
// The ElevationTile data has this layout:
// * 0 - magic id (0x12345678)
// * 4 - min elevation in meters (float)
// * 8 - tile elevation range in meters (float)
// * 12 - normalized elevation values (ushorts - 257*257 entries).
var minElevationInMeters = BitConverter.ToSingle(elevationTileData, 4);
var elevationRangeInMeters = BitConverter.ToSingle(elevationTileData, 8);
var elevationTile =
ElevationTile.FromNormalizedData(
tileId,
257,
257,
minElevationInMeters,
elevationRangeInMeters,
elevationTileData,
12 /* offset */);
// No async code was required so wrap in Task.
return(Task.FromResult(elevationTile));
}