Ground Overlays

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Ground overlays are image overlays that are tied to latitude/longitude coordinates, so they move when you drag or zoom the map.

Code samples

The ApiDemos repository on GitHub includes a sample that demonstrates ground overlays:

• GroundOverlayDemoActivity - Java: Ground overlay features and listeners in Java
• GroundOverlayDemoActivity - Kotlin: Ground overlay features and listeners in Kotlin

Introduction

A ground overlay is an image that is fixed to a map. Unlike markers, ground overlays are oriented against the Earth's surface rather than the screen, so rotating, tilting or zooming the map will change the orientation of the image. Ground overlays are useful when you wish to fix a single image at one area on the map. If you want to add extensive imagery that covers a large portion of the map, you should consider a Tile overlay.

Add an overlay

To add a GroundOverlay, create a GroundOverlayOptions object that defines both an image and a position. You can optionally specify additional settings that will affect the positioning of the image on the map. Once you've defined the necessary options, pass the object to the GoogleMap.addGroundOverlay() method to add the image to the map. The addGroundOverlay() method returns a GroundOverlay object; you should retain a reference to this object if you want to modify it later.

Note: When the image is added to the map it will be converted to an image with sides that are powers of two. You can avoid this conversion by using an original image with dimensions that are powers of two — for example, 128x512 or 1024x1024.

Step by step:

1. Instantiate a new GroundOverlayOptions object
2. Specify the image as a BitmapDescriptor.
3. Set the position of the image using one of the available methods:
   • position(LatLng location, float width, float height)
   • position(LatLng location, float width)
   • positionFromBounds(LatLngBounds bounds)
4. Set any optional properties, such as transparency, as desired.
5. Call GoogleMap.addGroundOverlay() to add the image to the map.

The below example demonstrates how to add a ground overlay to an existing GoogleMap object.

Kotlin

val newarkLatLng = LatLng(40.714086, -74.228697)
val newarkMap = GroundOverlayOptions()
    .image(BitmapDescriptorFactory.fromResource(R.drawable.newark_nj_1922))
    .position(newarkLatLng, 8600f, 6500f)
map.addGroundOverlay(newarkMap)

      

Java

LatLng newarkLatLng = new LatLng(40.714086, -74.228697);

GroundOverlayOptions newarkMap = new GroundOverlayOptions()
    .image(BitmapDescriptorFactory.fromResource(R.drawable.newark_nj_1922))
    .position(newarkLatLng, 8600f, 6500f);
map.addGroundOverlay(newarkMap);

      

If you wish to change or remove a ground overlay after you've added it to the map, ensure that you keep hold of the GroundOverlay object. You can modify the overlay later by making changes to this object.

Kotlin

// Add an overlay to the map, retaining a handle to the GroundOverlay object.
val imageOverlay = map.addGroundOverlay(newarkMap)

      

Java

// Add an overlay to the map, retaining a handle to the GroundOverlay object.
GroundOverlay imageOverlay = map.addGroundOverlay(newarkMap);

      

Remove an overlay

You can remove a ground overlay with the GroundOverlay.remove() method.

Kotlin

imageOverlay?.remove()

      

Java

imageOverlay.remove();

      

Change an overlay

You can change the ground overlay image after it's been added to the map with the GroundOverlay.setImage(BitmapDescriptor) method.

Kotlin

// Update the GroundOverlay with a new image of the same dimension
imageOverlay?.setImage(BitmapDescriptorFactory.fromResource(R.drawable.newark_nj_1922))

      

Java

// Update the GroundOverlay with a new image of the same dimension
imageOverlay.setImage(BitmapDescriptorFactory.fromResource(R.drawable.newark_nj_1922));

      

The setImage() method will replace the existing image with another image of the same dimensions.

Position a Ground Overlay

There are two ways to specify the position of the ground overlay:

• Using a LatLng to center the overlay, and dimensions in meters to specify the size of the image.
• Using a LatLngBounds to specify the north east and south west corners of the image.

You must specify the position of the ground overlay before it is added to the map.

Use location to position an image

When you add the image you specify a LatLng to which the anchor will be fixed and the width of the overlay (in meters). The anchor defaults to the center of the image. You can optionally provide the height of the overlay (in meters). If you do not provide the height of the overlay, it will be automatically calculated to preserve the proportions of the image.

The below code places an image at position 40.714086, -74.228697 that is 8.6km wide by 6.5km high. The image is anchored at the bottom left.

Kotlin

val newarkMap = GroundOverlayOptions()
    .image(BitmapDescriptorFactory.fromResource(R.drawable.newark_nj_1922))
    .anchor(0f, 1f)
    .position(LatLng(40.714086, -74.228697), 8600f, 6500f)

      

Java

GroundOverlayOptions newarkMap = new GroundOverlayOptions()
    .image(BitmapDescriptorFactory.fromResource(R.drawable.newark_nj_1922))
    .anchor(0, 1)
    .position(new LatLng(40.714086, -74.228697), 8600f, 6500f);

      

Use LatLngBounds to position an image

You provide a LatLngBounds which contains the image. The LatLngBounds sets the north east, and south west corners of the image. When the image is drawn on the map it will be rotated to fit the bounds. If the bounds do not match the original aspect ratio, the image will be skewed.

The below code places an image on the map with its South West corner bound to 40.712216,-74.22655 and its North East corner bound to 40.773941, -74.12544.

Kotlin

val newarkBounds = LatLngBounds(
    LatLng(40.712216, -74.22655),  // South west corner
    LatLng(40.773941, -74.12544)   // North east corner
)
val newarkMap = GroundOverlayOptions()
    .image(BitmapDescriptorFactory.fromResource(R.drawable.newark_nj_1922))
    .positionFromBounds(newarkBounds)

      

Java

LatLngBounds newarkBounds = new LatLngBounds(
    new LatLng(40.712216, -74.22655),       // South west corner
    new LatLng(40.773941, -74.12544));      // North east corner
GroundOverlayOptions newarkMap = new GroundOverlayOptions()
    .image(BitmapDescriptorFactory.fromResource(R.drawable.newark_nj_1922))
    .positionFromBounds(newarkBounds);

      

Associate data with a ground overlay

You can call GroundOverlay.setTag() to store an arbitrary data object with a ground overlay, and retrieve the data object using GroundOverlay.getTag().

The following code sample stores a string description with a ground overlay:

Kotlin

val sydneyGroundOverlay = map.addGroundOverlay(
    GroundOverlayOptions()
        .image(BitmapDescriptorFactory.fromResource(R.drawable.harbour_bridge))
        .position(LatLng(-33.873, 151.206), 100f)
        .clickable(true)
)
sydneyGroundOverlay?.tag = "Sydney"

      

Java

GroundOverlay sydneyGroundOverlay = map.addGroundOverlay(new GroundOverlayOptions()
    .image(BitmapDescriptorFactory.fromResource(R.drawable.harbour_bridge))
    .position(new LatLng(-33.873, 151.206), 100)
    .clickable(true));

sydneyGroundOverlay.setTag("Sydney");

      

Here are some examples of scenarios when it's useful to store and retrieve data with ground overlays:

• Your app may cater for different ground overlays, and you want to treat them differently when the user clicks them.
• You may be interfacing with a system that has unique record identifiers, where the overlays represent specific records in that system.
• The overlay data may indicate a priority to determine the z-index for the overlay.

Handle ground overlay events

By default, ground overlays are not clickable. You can enable and disable the clickability by calling GroundOverlay.setClickable(boolean).

Use an OnGroundOverlayClickListener to listen to click events on a clickable ground overlay. To set this listener on the map, call GoogleMap.setOnGroundOverlayClickListener(OnGroundOverlayClickListener). When a user clicks on a ground overlay, you will receive an onGroundOverlayClick(GroundOverlay) callback.

Note: If multiple overlays or shapes (markers, polylines, polygons, circles and/or ground overlays) are overlaid on top of each other, the click event is cycled through the cluster of markers first, then triggered for other clickable overlays or shapes based on their z-index values. At most one event is triggered per click. In other words, the click is not passed down to the overlays or shapes with lower z-index values. Read more about marker z-index and click events.