Long-term datasets of satellite data are very useful in ongoing studies, particularly in the field of Change Detection.
This data allows scientists to examine an area over a period of time, and see what changes (if any) are indicated, and determine the cause. Not only are the data of use in studying the past, but they can be used to forecast future changes based on past trends.
Deforestation, Polar ice loss and Climate Change studies all make use of satellite data to monitor their particular fields. The rate and extent of forest loss and ice melt can be tracked, as well as overall trends of change in our world's climate.
ESA has developed a large archive of this data from their satellites, particularly the two ERS missions and Envisat. Combined, the three satellites acquired data over the Earth for a period of 31 years. And from 2014 the Sentinel satellites will add to this archive with new imagery.
Beyond static comparisons of images acquired over the duration of the mission, methods have been developed to merge these images. They can be combined into one "multi-temporal" image that highlights the changes in a location over a period of time.
Latest Change Detection Events
19 April 2018 - Lake Mead is featured in this Landsat comparison. Using images acquired by the Landsat 5 and 8 satellites 27 years apart, the comparison shows that Lake Mead has undergone significant shrinkage since 1991.
12 April 2018 - The Aral Sea is featured in this Landsat comparison. Using images acquired by the Landsat 7 and 8 satellites 18 years apart, the comparison shows the Aral Sea has undergone significant shrinkage since 2000.
23 March 2018 - Floods struck Bolivia in recent weeks, following prolonged periods of torrential rain. Sentinel-1B was used to monitor the flood situation over Santa Ana del Yacuma and Trinidad before and after the flood.
15 March 2018 - Sentinel-1 and -2 show the southernmost city in Argentina, Ushuaia - also known as the "End of the World" - in this image comparison, which examines the city with optical and radar instruments.
08 March 2018 - Parts of Italy experienced heavy snowfall in February, and the Sentinel-2 mission captured a view of the aftermath. The image comparisons show how Arezzo, San Marino and Bologna looked before and after the snow.
23 February 2018 - Copenhagen, the capital city of Denmark is featured in this Sentinel comparison. In this image comparison, the Copenhagen is shown using the Sentinel-1 and -2 satellites to emphasise the difference between the radar and optical imagery the Sentinels provide.
09 February 2018 - Adam's Bridge is featured in this Landsat image comparison. Once a land bridge connecting India and Sri Lanka, it was destroyed by a cyclone, only to re-emerge as a series of islands centuries later. These Landsat 5 and 8 images show how the former bridge has changed since 2006.
02 February 2018 -The city of Dubai in the United Arab Emirates is featured in this Landsat comparison. Using images acquired by the Landsat 5 and 8 satellites 26 years apart, the comparison shows Dubai has undergone significant growth since 1991.
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