Earth selfies: using satellite images to track urban expansion
Freely available satellite images is a great resource for researchers. Usually being used by climate scientists or military issues, they can be used to track urban expansion or determine the "real" boundaries of cities in contraposition to "administrative" boundaries.
For example, I created an image to see how Spanish cities would look like if they had an administrative/political boundary matching the real boundary (defined as an urban continuum):
For example, I created an image to see how Spanish cities would look like if they had an administrative/political boundary matching the real boundary (defined as an urban continuum):
Another interesting feature is tracking this urban continuum over time. Here I created two images of my city, Barcelona:
It hasn't changed that much, right? That's because Barcelona is surrounded by the sea on the east, mountains on the west and other cities in the north and south of the administrative boundaries. In addition, we can see some expansions following the coast and some inner places. However, what is (even) more interesting is looking at other parts of the world.
Have you ever wondered if the effect of political regimes can be seen from the space? Thinking about it I created two images to see how North and South Korea look like from space and how both have evolved:
Have you ever wondered if the effect of political regimes can be seen from the space? Thinking about it I created two images to see how North and South Korea look like from space and how both have evolved:
Yet, another interesting example is the urbanization process of China. Here I have used two images of China where you can see the evolution of cities around Yangtze delta (Shanghai) and the Pearl River (Hong Kong, Macau, Shenzhen, etc.).
Of course, satellite images can be used for much more than just creating curious pictures to post on a personal website. Being raster images, one can extract quantitative values of pixels using a light gradient and then correlate it with other variables such as GDP, population, urban sprawl, etc. On the private sector side, we can analyze car parks outside big-box retailers such as Walmart to get a sense of daily revenues or estimate the productivity of factories by tracking the number of lorries parked outside.
At the end, satellite images are much more than just Earth selfies.
At the end, satellite images are much more than just Earth selfies.
