We’ve all grown so accustomed to seeing the world from space that we sometimes forget just how complex earth observation is. Truth is, it’s really hard to do anything in space – let alone try to capture high resolution and accurate pictures of the earth’s surface. This inescapable reality makes what we’re doing here at DigitalGlobe just that much more amazing.
Our Earth imaging satellites take pictures with 50cm resolution or better. That means each individual pixel in the image covers 50cm – about the equivalent ground area of home plate on a baseball field. This might not sound so impressive at first, especially when you compare it to the camera in your iPhone. If you stood over home plate and took a picture of it, each pixel would cover about 1/4mm distance.
But to be fair, that picture would be taken from about 1.5m (5 feet) above the ground. To compare apples to apples – no pun intended – you’d need to travel with your iPhone to the very edge of space. At that height, each pixel would cover about 400m of distance on the earth’s surface, or about a ¼ mile. That’s enough area to fit 18 Major League Baseball fields into each square pixel. With that kind of resolution, you’d be able to see land masses and clouds but really nothing else.
It’s remarkable that our satellites achieve this incredible image clarity from an altitude of about 700km (435 miles) above the earth, which is kind of like taking a picture from the top of Pikes Peak here in Colorado and being able to see cars in the parking lot of a Las Vegas casino. That is one big telephoto lens! But wait… it gets better. The satellite that’s taking that picture is zipping along at 27,000km (17,000 miles) per hour – fast enough to get you from London to Paris in under a minute. Imagine trying to keep your camera steady at that speed.
Getting a satellite up into space is a whole different challenge. The orbital window into which we place one of our satellites is about 2 square kilometers. Properly positioning a satellite in that small patch of outer space is the equivalent of throwing a football through a truck tire from seven football fields away. When you consider that each satellite weighs as much as an Asian elephant (2800kg, or 3 tons) and is the size of a ‘short’ school bus, you can understand how difficult the whole launch process is.
Each of our satellites orbits the Earth around 16 times and collects over 3,000,000 square kilometers (1,158,306 square miles) of imagery per day. When you combine the constellation, that’s enough imagery to cover the entire country of India every single day! And since our satellites never stop working, over time this adds up to an incredible amount of data. Our library of images collected over the last 15 years contains nearly 90 petabytes of data. If you put all this information on CDs (remember those?) and lined them up end to end, they would reach from Prudhoe Bay, Alaska, to Tierra Del Fuego, Chile – a distance of 14,654km (9,100 miles).
Earth orbit is a crowded place these days. There are over 1,100 active satellites circling the globe, and another 2,600 or so that are no longer working but still in orbit. Of all of these satellites, only the DigitalGlobe constellation can offer customers sub-50cm images that really capture the rich detail of our ever-changing planet.
Ready to learn more? Check out the video below for an overview of how satellite imagery is collected. Also learn how we make sense of satellite sensors by benchmarking a few capabilities like accuracy and spatial, spectral and temporal resolution.
I hope you’ve enjoyed reading these fun facts about our satellites as much as I’ve enjoyed doing all this math. Now, if you’ll excuse me, I’m going to go try to throw a football through a truck tire. Wish me luck.