Monday, 14 July 2014

Photo: São Paulo seen from space

São Paulo as seen from the International Space Station
Taken by NASA from the International Space Station the photo of São Paulo (above) shows us what the city looks like when viewed from orbit.

As a huge urban area, it is easy to pick out although getting a good shot is easier said than done. Due to the earth's orbit the city flies by at a speedy 4.4 miles per second. If we do the maths that means that even at a very fast exposure of 1/1000th of a second there is still 7 metres of Earth motion.

The trick behind the São Paulo picture, and other photos taken from space, is similar to high speed sports photography. The camera is panned in the opposite direction to the natural orbit of the earth but at exactly the same speed thereby compensating the effect which would ordinarily cause blur or streaking.

The result is a photo which clearly shows São Paulo's main arteries as well its geographical footprint. You may notice blue-green lighting in and around the centro region and yellow-orange lighting on the outskirts. The reason for this is mercury-vapor lighting is more prevalent int the old centre whereas sodium vapor lighting is common in more recently built areas. 

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