// Initialize viewshed analysis and add it to the view.
      const viewshedAnalysis = new ViewshedAnalysis();
      viewElement.analyses.add(viewshedAnalysis);

      // Create the viewshed shape programmatically and add it to the analysis.
      const programmaticViewshed = new Viewshed({
        observer: {
          spatialReference: SpatialReference.WebMercator,
          x: -9754426,
          y: 5143111,
          z: 330,
        },
        farDistance: 900, // In meters
        tilt: 84, // Tilt of 0 looks down, tilt of 90 looks parallel to the ground, tilt of 180 looks up to the sky
        heading: 63, // Counted clockwise from North
        horizontalFieldOfView: 85,
        verticalFieldOfView: 60,
      });
      viewshedAnalysis.viewsheds.add(programmaticViewshed);

      // Access the viewshed's analysis view.
      const analysisView = await viewElement.whenAnalysisView(viewshedAnalysis);

      // Controller for aborting the viewshed place operation.
      let abortController = null;

      placeButton.addEventListener("click", () => startPlacing());

      async function startPlacing() {

        // Create a new abort controller for the new operation.
        abortController = new AbortController();
        const { signal } = abortController;

        // Pass the controller as an argument to the interactive place method.
        try {
          await analysisView.place({ signal: abortController.signal });
        } catch (error) {
          // This is used to handle the case when the viewshed placement is aborted.
          if (!promiseUtils.isAbortError(error)) {
            throw error;
          }
        } finally {
          if (abortController && abortController.signal === signal) {
            abortController = null;
          }
          updateUI();
        }
      }

      cancelButton.addEventListener("click", () => stopPlacing());

      function stopPlacing() {
        abortController?.abort();
        abortController = null;
        updateUI();
      }

        if (viewshed.horizontalFieldOfView > horizontalLimit) {
          viewshed.horizontalFieldOfView = horizontalLimit;
        }

        if (viewshed.verticalFieldOfView > verticalLimit) {
          viewshed.verticalFieldOfView = verticalLimit;
        }

      function getCameraFromViewshed(viewshed) {
        return new Camera({
          position: viewshed.observer,
          heading: viewshed.heading,
          tilt: viewshed.tilt,
          // Calculate camera's diagonal field of view angle.
          fov: getDiagonal(viewshed.verticalFieldOfView, viewshed.horizontalFieldOfView),
        });
      }
      function getDiagonal(a, b) {
        return Math.sqrt(a ** 2 + b ** 2);
      }