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
11 January 2018 - The Kansai International Airport of Osaka, Japan is featured in this Sentinel comparison. In this image comparison, the airport is shown using the Sentinel-1 and -2 satellites to emphasise the difference between the radar and optical imagery the Sentinels provide.
18 December 2017 - A large forest fire is raging in Montecito County in California. Known as the Thomas Fire, it has affected more than a thousand buildings and firefighters are working to extinguish the flames. Natural and false-colour Landsat 8 imagery was used to compare the area before and after the fires began; demonstrating the scale of the fire in the first week of December.
01 December 2017 - These Landsat-8 and Sentinel-2 images show Monfalcone in Italy, to commemorate the launch of the Seaside, the largest Italian cruise ship ever built. The vessel was launched on 29 November, and these images show the Seaside and its sister ship in drydock at Monfalcone in different resolutions.
23 November 2017 - Marseille, the capital city of Bouches-du-Rhône department, is pictured in this Landsat image comparison. These Landsat 5 and 8 images show that Marseille has undergone significant growth since 1984.
13 November 2017 - Barcelona, the capital city of Catalonia, is pictured in this Landsat image comparison. These Landsat 5 and 8 images show that Barcelona has undergone significant growth since 1984.
03 November 2017 - European Space Week is being held at Tallinn in Estonia from 03-09 November. In this image comparison, Tallin is shown using the Sentinel-2 and -1 satellites to emphasize the difference between the optical and radar imagery.
26 October 2017 - The historic city of Istanbul is featured in this Landsat comparison. Using images acquired by the Landsat 5 and 8 satellites 31 years apart, the comparison shows how much this Turkish city has grown since 1986.
20 Oct 2017 - This Landsat-8 image comparison, acquired on 14 October 2017, shows wildfires North-East of Vigo in Spain. A combination of natural and false colour imagery is used to show how Vigo forest has been affected by the fires.
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