Using Google Earth to Plan High-Resolution Satellite Image Data

Google Earth is a great addition to the growing set of software solutions devoted to viewing satellite image data from around the world. While Google Earth satellite imagery doesn't match the quality of traditional high-resolution satellite images, it is an excellent way to determine the coordinates of a location you'd like to study further.

A Brief History of Google Earth

In 2004, Google acquired Keyhole Corporation, a digital mapping company whose Keyhole Viewer maps program united traditional satellite imagery, digital aerial photography, and GIS resources from around the globe into one convenient software application.

Shortly after, in 2005, Google repackaged the software as Google Earth and made the software available for free download from the Google site. Today, Google Earth exists in several different formats: a free, non-commercial version, Google Earth Plus, which adds support for GPS devices, data importing, and better printing; and Google Earth Pro, which includes, among other enhancements, faster performance, better measurement tools, and a module to create fly-in movies. Today, many television news networks utilize the fly-in movie feature to zoom to a location.

Image Quality: Google Earth vs. Custom Satellite Imagery

While the image quality of Google Earth far surpasses anything that has been available at the free consumer level in the past, it still doesn't come close to matching the detail and quality of a custom high-res satellite photo shot by one of the major satellites, such as QuickBird at 0.6m, IKONOS at 0.8m or SPOT-5 at 2.5m resolution.

Following is an image of the Hurghada beachfront in Egypt, shot with DigitalGlobe's QuickBird satellite via Google Earth:

Please click the thumbnail to enlarge.

Next, view a satellite photo from Satellite Imaging Corporation's QuickBird image gallery:

Please click the thumbnail to enlarge.

Now, compare the following satellite photographs of the Lagos, Nigeria airport. The first image was available through Google Earth:

Please click the thumbnail to enlarge.

The following image of the same location was captured by Satellite Imaging Corporation:

Please click the thumbnail to enlarge.

On close inspection of the images, some differences become clear. The Google Earth image, while an accurate representation of the area, is distinct in several ways:

• Unified image quality. The center of the image is where the image is sharpest, while the outlying regions of the photo become increasingly blurry as you move to the edges.
  
  
• Timely and current. While Google Earth lists its images as "approximately one to three years old," users are never entirely sure the date an image was shot. This might be fine for satellite photographs of established, urban areas, but for some projects, such as erosion monitoring or residential development, knowing the exact date on which an image was taken is essential.
  
  The images in SIC's image library are date-stamped, so you are never in doubt as to how recently the image was photographed. If no image of your target area exists in our library, or if you need to monitor changes over time, we can easily order a custom satellite image to be taken, which ensures that your image is as current as technology allows.
  
  
• Worldwide availability. Currently, Google Earth provides high-resolution image data for major metropolitan areas, and often, little else. Unfortunately, outlying areas are often a major source of interest for civil engineers, oil and gas exploration teams, and environmental project managers. Satellite Imaging Corporation provides high-resolution for nearly any location on earth, not just major cities.

Using Google Earth to Preview Your Custom Satellite Photograph

In the satellite imagery field, we call it the "Area of Interest." That's really just shorthand for the location you want to be photographed. It might be an existing neighborhood, down to the exact street address. It might be a corporate campus or vacant lot. It might be a location in the middle of nowhere, perhaps soon to be an oil field, residential development, or protected wetland.

Regardless of the location, satellite imagery is shot based on Latitude and Longitude coordinates, not by street address. Google Earth is a great help in determining the exact coordinates that you need for your image.

The following notes explain how to utilize Google Earth to determine the exact coordinate boundaries of your "Area of Interest." In the sample image below, we've used the address of Apple Computer's campus in Cupertino, CA - 1 Infinite Loop.

• If Google Earth has not been installed on your computer, please install it first. Read installation and computer requirements carefully to ensure that your system is powerful enough (in terms of hard drive space and RAM) to run Google Earth properly.
  
  
• In the upper-left part of the screen, select the "Fly To" option and enter a street address, town/village, state or province, and country. Google Earth will automatically take you to the area selected.
  
  
• When you contact us to tell us about your "area of interest," we need two sets of numbers - the latitude and longitude coordinates of the opposite corners of your intended photograph. In other words, in the sample graphic above, we need the latitude/longitude coordinates of corners A and D or the coordinates of corners B and C. Knowing the coordinates of two opposing corners enables us to create the rectangular image correctly.
  
  
• The WGS-84 latitude and longitude coordinates for your location appear at the bottom of the active Google Earth window on the left side. In the image above, the latitude is highlighted in the red rectangle, and the longitude is in the green rectangle. Remember that the coordinates shown on the screen are the coordinates of your mouse pointer on the screen (shown as a "hand" icon in the yellow rectangle), so be sure to place it correctly. Don't assume that the coordinates shown on the screen are the center of the image or the exact street address you requested, because they probably are not.
  
  
• As an additional option, you can also make a screenshot of the active window and provide us the image in JPEG format as an attachment to your message, along with your request. Send the information to: info@satimagingcorp.com