Edit KML ground overlay

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Sample viewer app

Edit the values of a KML ground overlay.

Image of edit KML ground overlay

Use case

KML ground overlays are used for showing aerial imagery, symbology, or other images draped over a scene. Changing the geometry, rotation, and other attributes of a ground overlay after it has been loaded allows for live editing. For example, editing the geometry and opacity of a historical image draped over present day satellite imagery makes it possible to view change over time.

How to use the sample

Use the slider to adjust the opacity of the ground overlay.

How it works

  1. Create an AGSEnvelope defining the geometry of the overlay.
  2. Create an AGSKMLIcon using a URL linking to an image.
  3. Create an AGSKMLGroundOverlay using the envelope and icon.
  4. Set the value of the overlay's rotation.
  5. Create an AGSKMLDataset using the ground overlay.
  6. Create an AGSKMLLayer using the dataset.
  7. Add the KML layer to the scene.
  8. As the value of the slider changes, adjust the overlay's color value appropriately.

Relevant API

  • AGSKMLDataset
  • AGSKMLGroundOverlay
  • AGSKMLIcon
  • AGSKMLLayer

About the data

The image used in this sample is an aerial view of the campus of the University of Oregon. This imagery was taken in 1944 by the U.S. Army Corps of Engineers. It is publicly available as Online Aerial Imagery hosted by Oregon University Library. It is also available as a Portal item on ArcGIS Online as University of Oregon Campus Aerial Imagery - 1944.

Tags

imagery, Keyhole, KML, KMZ, OGC

Sample Code

EditKMLGroundOverlayViewController.swift
                                                                                  
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// Copyright 2020 Esri
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

import UIKit
import ArcGIS

class EditKMLGroundOverlayViewController: UIViewController {
    // MARK: Storyboard views and properties
    @IBOutlet var sceneView: AGSSceneView! {
        didSet {
            sceneView.scene = makeScene(groundOverlay: overlay)
            // Move the viewpoint to the ground overlay.
            let targetExtent = overlay.geometry as! AGSEnvelope
            let camera = AGSCamera(lookAt: targetExtent.center, distance: 1250, heading: 45, pitch: 60, roll: 0)
            sceneView.setViewpoint(AGSViewpoint(targetExtent: targetExtent, camera: camera))
        }
    }
    // The slider that controls the overlay's opacity.
    @IBOutlet var opacitySlider: UISlider!
    // The label that displays the slider's value.
    @IBOutlet var valueLabel: UILabel!

    // A number formatter to format the opacity value.
    let numberFormatter: NumberFormatter = {
        let numberFormatter = NumberFormatter()
        numberFormatter.minimumFractionDigits = 2
        numberFormatter.maximumFractionDigits = 2
        return numberFormatter
    }()

    // The KML ground overlay.
    let overlay: AGSKMLGroundOverlay = {
        // Create a geometry for the ground overlay.
        let overlayGeometry = AGSEnvelope(xMin: -123.066227926904, yMin: 44.04736963555683, xMax: -123.0796942287304, yMax: 44.03878298600624, spatialReference: .wgs84())
        // Create a KML icon for the overlay image.
        let imageURL = URL(string: "https://libapps.s3.amazonaws.com/accounts/55937/images/1944.jpg")!
        let overlayImage = AGSKMLIcon(url: imageURL)
        let overlay = AGSKMLGroundOverlay(geometry: overlayGeometry, icon: overlayImage)!
        // Set the rotation of the ground overlay.
        overlay.rotation = -3.046024799346924
        return overlay
    }()

    // MARK: Actions and methods
    @IBAction func sliderValueChanged(_ slider: UISlider) {
        // Change the color of the overlay according to the slider's value.
        let alpha = CGFloat(slider.value)
        overlay.color = UIColor.black.withAlphaComponent(alpha)
        // Update the slider's value label.
        valueLabel.text = numberFormatter.string(from: slider.value as NSNumber)
    }

    func makeScene(groundOverlay: AGSKMLGroundOverlay) -> AGSScene {
        // Create a scene for the scene view.
        let scene = AGSScene(basemap: .imagery())
        // Create a KML dataset with the ground overlay as the root node.
        let dataset = AGSKMLDataset(rootNode: groundOverlay)
        // Create a KML layer for the scene view.
        let layer = AGSKMLLayer(kmlDataset: dataset)
        // Add the layer to the scene.
        scene.operationalLayers.add(layer)
        // Return the scene.
        return scene
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        // Add the source code button item to the right of the navigation bar.
        (navigationItem.rightBarButtonItem as? SourceCodeBarButtonItem)?.filenames = ["EditKMLGroundOverlayViewController"]
    }
}

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