Thanks to satellite technology, billions of fans will be watching the World Cup soccer competition over the next month - but satellites of a different kind have been keeping an eye on South Africa's World Cup stadiums for months already. And you can get a triple dose of high-resolution imagery via the Web.

Three of the world's top Earth-imaging ventures - GeoEye, DigitalGlobe and Spot Image - have put together separate galleries showing all 10 of the venues for World Cup action.

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You'll find GeoEye's set, based on observations from the GeoEye-1 and Ikonos satellites, at the company's website. We've also adapted five of the images in a slideshow that uses Microsoft's HD View zoom feature. (Microsoft and NBC Universal are partners in the msnbc.com joint venture.)

Both of GeoEye's satellites took pictures from an altitude of 423 miles as they zoomed over Africa at 4 miles a second in a pole-to-pole orbit. GeoEye-1's half-meter resolution is twice as sharp than Ikonos' 1-meter-per-pixel resolution. Can you tell the difference?

DigitalGlobe has put its World Cup set on Flickr. The gallery includes a double-take for Mbombela Stadium, with images from the under-construction stage in January as well as from the ready-for-business stage last week. DigitalGlobe gets half-meter-resolution imagery from the QuickBird satellite as well as from WorldView-1 and WorldView-2.

On its website, Spot Image offers a gallery of the 10 stadiums plus a YouTube video that takes you quickly through the whole set. If you watch it on YouTube, optimize the image size for the best view (not too small, but not too big and pixellated, either). These pictures were provided by Kompsat-2, a South Korean satellite that provides 1-meter-resolution black-and-white views as well as 4-meter-resolution color imagery.

Discovery News' Michael Reilly points out the historical context behind the imagery: The Soccer City Stadium, for example, was where Nelson Mandela gave his first speech after being released from prison in 1990. Today, the 94,700-seat stadium served as the site for the World Cup's opening game. In NASA's EO-1 satellite image, you can see the slag heaps and slums that still surround the world-class venue. (Sadly, Mandela had to cancel his plans to attend the opener, and instead mourned the death of his 13-year-old great-granddaughter in a car crash.)

GeoEye spokesman Mark Brender told me there were no plans to snap satellite photos of the stadiums during the World Cup's actual run. Because of the timing of the satellites' orbits, there wouldn't be much to see when they passed over the venues each morning, he said. Besides, there are no clients willing to pay for the pictures. After all, the satellite business is a business.

But it's more than just a business, and the pictures aren't always pleasant: Satellite imagery is routinely used by government agencies and charities to map out the response to disasters such as the Haiti earthquake or the Gulf oil spill, and the U.S. government is known to supplement its own satellite resources with pictures from the private sector. In the end, it's not about what happens in space; it's all about what happens on Earth.

"To understand something, one must first observe," Brender told me. "Our satellite imagery is an observational tool that provides insight to what is happening on the ground."

More about sports and space imagery:

• Astronauts catch World Cup mania
• NASA satellite spots Soccer City Stadium
• See the oil spill from space

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