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User Guide




Using Image Overlays and 3D Models

With Google Earth, you can place custom images and Google SketchUp 3D models over the view of the earth. Image overlays provide additional information about the underlying earth imagery. For example, you can:

Google SketchUp is software that allows users to create 3D models and share them with others. For more information about Google SketchUp, visit the product home page. Also refer to the following topics:

About Overlays

When you create an image overlay, you are specifying three important things:

The topics in this section cover:

Tip - You can hide an existing image overlay by unchecking it the Places panel. To permanently delete an image overlay, right-click on it in the Places panel and choose Delete. Learn more about using places and folders.

Overlay Requirements

Overlay images can be taken from your computer, from your network, or from a web site. The image format must be:

Overlays in PNG and GIF formats can be modified so that undesirable regions (such as image boundaries) are transparent, letting the underlying imagery show through.

You can use topographical maps, weather satellite image maps, or other geographical image data as overlays. For ideas and examples of overlays, see the Google Earth Community bulletin board (bbs.keyhole.com).

The overlay image itself must have a North-Top orientation with simple cylindrical projection. Simple cylindrical projection (or Plate Carrée) is a simple map projection where the meridians and parallels are equidistant, straight parallel lines, with the two sets crossing at right angles. (This format is also known as Lat/Lon WGS84 projection.) Because a certain amount of modifications to overlay images is allowed, you might find that the more common UTM maps work well enough over small areas. However, for a more precise overlay of a large region, simple cylindrical projection is required.

Note - The overlay feature is memory intensive. Consequently, images larger than 2000x2000 pixels can reduce the performance of Google Earth and other applications currently running on your computer. (To determine the size in pixels of an image, display the image file in a Windows Explorer window, right-click (CTRL click on the Mac) on it, and select Properties from the pop-up menu.) If you are having trouble importing a large image, you can reduce its size using image editing software such as Adobe Photoshop.

Overlay Features

Once you create an overlay, it has many of the same features available to it as a simple placemark. With overlays, you can:

In addition to common placemark features, image overlays also have the following features:

Transparency Adjustment - You can adjust the transparency of an overlay from completely transparent to fully opaque whenever it is selected in the viewer. By adjusting the transparency of the overlay image, you can see how the overlay image corresponds to the 3D viewer imagery beneath.

Transparency Adjustment

  1. Overview slider for selected overlay
Note - You can also adjust the transparency of a selected overlay if your mouse has a scroll wheel. Click the slider (see above). Scroll down to make the overlay more opaque. Scroll up to make the overlay more transparent, .

Terrain Integration

When you create an overlay, it completely integrates with the terrain or shape of the land beneath if the terrain layer is turned on. For example, you might create an overlay of Yosemite National Park and be able to view the trails in relationship to the 3D view of the mountains. In this way, the combination of an overlay map and the 3D viewer imagery gives more information than either one by itself.

Overlay Map with Terrain Off
Overlay map with terrain off

Overlay Map with Terrain On

Overlay map with terrain on

Creating an Image Overlay

This section covers three parts to creating an image overlay:

Creating an Overlay

  1. Position the 3D viewer in the location where you want to place the overlay image file.

    Try to position the viewer so that it corresponds in viewing altitude to the overlay. If the overlay is of a detailed view, zoom into the subject area so that you don't have to make large adjustments later. By contrast, if the overlay covers a large area, make sure the entire area is encompassed in the 3D viewer with some margins for adjusting the imagery.
  2. Select Image Overlay from the Add menu (or use other shortcut methods described in Creating A New Placemark). The New Image Overlay dialog box appears.
  3. Provide a descriptive name in the Name field.
  4. In the Link field, enter the location of the image file you want to use as an overlay or use the Browse button to locate it on your computer or network.

  5. If the image you are referencing is located on the Web, you will need to enter the URL for that image file. This is different from the URL for the web page itself! If you are using Internet Explorer, you can retrieve the URL for an image by right-clicking on the image on its web page and selecting Copy Shortcut from the pop-up menu. At that point, you can insert your cursor in the Image URL or Filename field and paste the information using Ctrl+V (Command/Open Apple Key on the Mac).

    Copy Image Location
    The image appears in the 3D viewer, with anchor points that you use to position it.
  6. Specify the descriptive information for the overlay. Descriptions for overlays are identical to descriptions for all places data. See Writing Descriptions for details.
  7. Click the Refresh tab and set the correct refresh properties for your overlay imagery. The refresh settings for overlays are identical to those described for network links. Typically, any imagery that is updated automatically and located on a server will need refresh properties set. For example, weather satellite image maps will likely need to be refreshed. For details on the differences between time-based and view-based refresh, see the description for network links.
  8. Set the default transparency for the imagery using the slider. The transparency setting for image overlays can be adjusted at any time when you are viewing an overlay. To make it easy to position the overlay, first adjust the transparency to achieve a good balance between seeing the imagery and the earth beneath it.
  9. When you select the View tab, you can modify the view settings for the overlay just as you would any place data. See Setting the View for details.
  10. Position the image in the viewer to your preferences and click OK to complete the creation. If you later want to correct the overlay or reposition it, simply edit the overlay as you would any other places data. See the topics in Editing Places and Folders for more information.

Positioning the Imagery in the Viewer

Once you have inserted the overlay image into the viewer, you can use the green markers to stretch and move the image in a number of ways to get the most exact positioning required. An overlay image will have corner and edge marks that you can use to stretch the image, a central cross hair marker to position the image, and a triangle marker that you can use to rotate the image.

When you select one of these markers, the cursor changes from an open hand to either a finger-pointing hand or an arrow to indicate that an anchor point is selected. The following illustration describes the anchor points in detail.

Positioning the Overlay in the Viewer

  1. Use the center cross-hair marker to slide the entire overlay on the globe and position it from the center. (Tip: do this first.)
  2. Use the triangle marker to rotate the image for better placement.
  3. Use any of the corner cross-hair markers to stretch or skew the selected corner. If you press the Shift key when selecting this marker, the image is scaled from the center.
  4. Use any of the four side anchors to stretch the image in or out of from the selected side. If you press the Shift key when doing this, the image is scaled from the center.
Tip - Try positioning the center of the image as a reference point first, and then use the Shift key in combination with one of the anchors to scale the image for best positioning.

Position settings

When you select the Location tab, you can use the following settings:

When you select the View tab, you can modify the view settings for the overlay just as you would any place data. See Setting the View for details.

Opening and Viewing Overlays

In addition to the overlays you create, you can also open and view overlays emailed to you by other Google Earth users, or you can view overlays posted to a web server.

Opening Overlays Emailed to You

Opening overlays emailed can be done in two ways:

Opening Overlays on a Web Server

You can open overlays posted to a web server simply by clicking on the link that references the overlay image. When you do this, a dialog box prompts you to select the correct application to open the attachment. By default, Google Earth should be selected. Click the appropriate button to confirm the selection. The image overlay appears in the 3D viewer and the item is displayed in the Temporary Places folder in the Places panel. You can save the overlay as described above.

Posting Image Overlays to a Web Server

You can share overlay data with other Google Earth users by posting the overlay file to a web server that other users also have access to. For example, Google Earth users can post overlays and placemark information to the Google Earth Community BBS (bbs.keyhole.com). The rest of this section covers the details of posting overlay data to the Google Earth BBS.

Note - You can post overlays to the Google Earth Community BBS regardless of whether they reference local or web-based imagery data. Overlays that you post to the BBS will automatically include images referenced from a local file system. This is an upgrade from Keyhole 2.2.
  1. Right-click (CTRL click on the Mac) on your overlay and select Save As... from the pop-up menu.
  2. Navigate to a location on your computer's hard drive using the Save dialog box, name the file, and save it.
  3. Use a web browser to connect to bbs.keyhole.com. You must be a registered user of the Google Earth Community to post overlay files. If you are a first-time user of the Google Earth software, you must first register with the Google Earth community before you can log in and post placemark files. This registration is a separate process from your Google Earth subscription and is free of charge:
    • Once on the Google Earth BBS, click on the registration link in the Login area.
    • Follow the on-screen instructions to register on the site.
    • You need to provide your email address in order to activate your account. After registering, an email will be sent to that address containing your registration information and an activation link.
    • Click on the link provided in your account activation email. Your bulletin board account is activated, and you have full access to all of the features of the Google Earth BBS.
  4. Log on to the Google Earth Community web site.
  5. Choose a forum (threaded discussion) that is relevant to your image overlay posting.
  6. Click the Post link in the forum subheader.
  7. Enter information in the Subject and Post fields, select the check box next to "I want to preview my post and/or attach a file" and click the Continue button.
  8. Preview your posting and attach an overlay file by clicking on the Browser button and navigating to the file.
  9. Click the Continue button to post your message and file.

Placing WMS Image Overlays

You can place Web Mapping Service (WMS) image overlays in Google Earth. These are mapping images that are provided through a WMS over the Internet. They can show you interesting information, such as weather formations and conditions, topographical maps, alternate high resolution satellite imagery and more.

To place an WMS image overlay:

  1. Follow Steps 1 and 2 of Creating an Image Overlay.
  2. In the New dialog box, click the Refresh tab.
  3. Click WMS Parameters. The Web Mapping Service Parameters dialog box appears.
  4. Beside WMS Service, choose an appropriate service or click Add to use a URL (website address) for a WMS. After a brief period of time, Google Earth populates the Opaque and/or Transparent Layers fields with available layers from the WMS you choose.
  5. Choose the appropriate layer(s) and click Add -> to add the layer(s) to the Selected Layers field. This places this information in the WMS image overlay you will see in Google Earth. To remove a layer from the Selected Layers field, select it and click <-Remove.
  6. To set the order of selected layers as they appear in the 3D viewer, select the appropriate layers in the Selected Layers field and click Move Up or Move Down.
  7. When you are finished, click OK and continue from Step 3 of Creating an Image Overlay.

Placing Google SketchUp 3D Models

To place a Google SketchUp 3D model in Google Earth:

  1. Click Add > Model or press Ctrl + Shift + M (Command/Open Apple Key+ Shift + M on the Mac). The New Model dialog box appears. Adding a model is very similiar to adding a placemark.
  2. Altitude settings for 3D models are identical to placemark altitude settings. For more information, see Setting Altitude.

For additional information:

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