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:
- Use a map of satellite weather data that updates to reflect the most recent weather imagery for that region.
- Use imagery of a site plan and plot boundaries to view the development stages over a particular plot.
- Use publicly available image maps (or create your own image maps) for such things as hiking trails, camping spots, theme parks, fishing locations, national park boundaries and more.
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 homepage. Also refer to the following topics:
About Overlays
Note - This feature is distinct from adding a photo to Google Earth.
When you create an image overlay, you are specifying three important things:
- What image file is to be displayed in the 3D viewer (from your computer, from your network or from a website)
- How to fit or position the image boundaries to the Earth data beneath
- The location and view of the imagery overlay (in the same way you do when positioning a new placemark)
The topics in this section cover:
Tip - You can hide an existing image overlay by un-ticking it in the Places panel. To permanently delete an image overlay, right-click 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 website. The image format must be one of the following:
- BMP
- DDS
- GIF
- JPG
- PGM
- PNG
- PPM
- TGA
- TIFF
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 geographic 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) 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:
- Email them to other people - You can email image overlays just as you would mail other placemark data. However, keep in mind that overlay files can only be opened by other users of Google Earth. If you want to send the overlay image as it appears on the Earth to someone who doesn't have Google Earth, email the view instead. For details on emailing overlays, see Emailing Place Data.
When you email an overlay that references a local image, that image is automatically included with the overlay. You do not need to include the local image in your email attachment. This is an upgrade from Google Earth (Keyhole) version 2.2 and earlier.
- Save them to your computer. See Saving Place Data for details.
- Edit their properties and settings - See Editing Places and Folders for relevant information.
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.
- 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 on
- Updates based on time or view coordinates - If you are viewing time-sensitive imagery that changes periodically, you can set the imagery to a refresh rate to make sure you are viewing the latest image. This is useful for viewing imagery maps from the web where the image is automatically updated.
In addition, you can set the imagery to update depending on your view. For example, you might be viewing imagery from a server that only delivers imagery that can be seen in your current 3D view. In this case, the imagery update changes whenever you navigate the 3D viewer to a new position.
- Draw Order - You can determine the hierarchy that Google Earth uses when you use overlapping image overlays. Google Earth displays images with a higher draw order number in front of images with a lower draw number.
Creating an Image Overlay
This section covers the three parts involved in creating an image overlay:
Creating an Overlay
- 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 in to 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 that the entire area is encompassed in the 3D viewer with some margins for adjusting the imagery.
- Select Image Overlay from the Add menu (or use other shortcut methods described in Creating A New Placemark). The New Image Overlay dialogue box appears.
- Provide a descriptive name in the Name field.
- In the Link field, enter the location of the image file that you want to use as an overlay or use the Browse button to locate it on your computer or network.
If the image that 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 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 (
on Mac).
The image appears in the 3D viewer, with anchor points that you use to position it.
- Specify the descriptive information for the overlay. Descriptions for overlays are identical to descriptions for all place data. See Writing Descriptions for details.
- 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 to have refresh properties set. For example, it's likely that weather satellite image maps will need to be refreshed. For details on the differences between time-based and view-based refresh, see the description for network links.
- 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.
- 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.
- Position the image in the viewer according to your preferences and click OK to complete the creation. If you want to correct the overlay or reposition it at a later stage, simply edit the overlay as you would any other place 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.
- Use the centre cross-hair marker to slide the entire overlay on the globe and position it from the centre. (Tip: do this first.)
- Use the triangle marker to rotate the image for better placement.
- 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 centre.
- Use any of the four side anchors to stretch the image in or out from the selected side. If you press the Shift key when doing this, the image is scaled from the centre.
Tip - Try positioning the centre 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:
- Manual coordinates for each corner of the image overlay. This is similar in principle to the manual setting discussed in Repositioning Placemarks, except that instead of setting coordinates for a single point, you set coordinates for each corner of the image overlay. You might want to use this feature if your image overlay comes from a precise map where the exact coordinates are known.
- Draw Order - If you have more than one overlay for a given region, you can set the draw order for overlays to determine which image is displayed relative to other images. Overlays with higher numbers are drawn before those with lower numbers.
- Fit to Screen - Click this to resize the image to fit the current view.
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 that you create, you can also open and view overlays that are emailed to you by other Google Earth users, or you can view overlays that are posted to a web server.
Opening Overlays Emailed to You
You can open overlays that have been emailed to you in two ways:
- Double-click the attachment in the email message. You'll receive a confirmation dialogue box to open the attachment in Google Earth. Click the appropriate button to open the attachment. If Google Earth is not running, it will start up before loading the emailed overlay. Otherwise, it appears in the Temporary Places folder in the Places panel and the image overlay displays in the viewer. You can save the overlay as you would any other place data. See Saving Place Data.
- Save the attachment to your computer. You can save the overlay file to your computer and open it at your convenience as you would any other type of place data. See Opening Saved Placemarks for details.
Opening Overlays on a Web Server
You can open overlays posted to a web server simply by clicking the link that references the overlay image. When you do this, a dialogue 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.
- Right-click (CTRL click on the Mac) your overlay and select Save As… from the pop-up menu.
- Navigate to a location on your computer's hard drive using the Save dialogue box, name the file and save it.
- 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 this is the first time that you've used the Google Earth software, you must 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 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 the link provided in your account activation email. Your bulletin board account will be activated, and you will have full access to all of the features of the Google Earth BBS.
- Log on to the Google Earth Community website.
- Choose a forum (threaded discussion) that is relevant to your image overlay posting.
- Click the Post link in the forum sub header.
- Enter information in the Subject and Post fields, select the checkbox next to "I want to preview my post and/or attach a file " and click the Continue button.
- Preview your posting and attach an overlay file by clicking the Browser button and navigating to the file.
- Click the Continue button to post your message and file.
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 a WMS image overlay:
- Follow Steps 1 and 2 of Creating an Image Overlay.
- In the New dialogue box, click the Refresh tab.
- Click WMS Parameters. The Web Mapping Service Parameters dialogue box appears.
- 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 that you choose.
- 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 that you will see in Google Earth. To remove a layer from the Selected Layers field, select it and click <-Remove.
- 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.
- 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:
- Click Add > Model or press Ctrl + Shift + M (+ Shift + M on the Mac). The New Model dialogue box appears. Adding a model is very similar to adding a placemark.
- Altitude settings for 3D models are identical to placemark altitude settings. For more information, see Setting Altitude.
For additional information:
