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Global wetlands surveyed from space

24 November 2003

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Wetlands across four continents will be the focus of study during ESA's Globwetland project. Wetlands fulfil a large number of very useful biological and hydrological functions but are increasingly under threat from human activities.

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Credits: Ramsar

Data gathered over four continents

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Visible in this MERIS image is Spain, which occupies most of the Iberian Peninsula. The long mountain chain of the Pyrenees, extending about 400 km from the Bay of Biscay to the Mediterranean Sea, forms the border with France on the north.

The large, almost treeless central plateau is the Meseta Central. With an average elevation of about 600 meters above sea level, it is divided by irregular mountain ranges, or sierras, including the Guadarrama, Gredos and Toledo mountains.

Technical Information:
Instrument: MEdium Resolution Imaging Spectrometer (MERIS)
Date of Acquisition: 23 March 2002
Orbit number: 306
Instrument features: Full resolution image (300-meter resolution).
With its 300-meter resolution imaging capabilities and outstanding radiometric accuracy, MERIS will help scientists and environmental agencies to understand better the causes and consequences of deforestation, erosion, river pollution and other environmental threats.

Credits: ESA 2002

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This ASAR APP image shows an area, 70.1 km wide by 105.2 km long, centred over the city of Volgograd, formerly Stalingrad, along the western bank of the Volga. In this image, the Volga -the longest river in Europe with a length of 3700 km- flows south from the top to the centre of the image, then east from the center to the right. Volgograd is the major River Volga port and the eastern terminus of the Volga-Don Canal.
Urban areas with sparse vegetation, like Volgograd in the western bank of the Volga, are generally visible in yellow-green tones indicating equally high backscatter in HH and HV. Blue tones in the image indicate low HH and HV backscattering, being the HV backscattering higher than HH, corresponding to the Volga River, channels, lakes or wet areas. The use of cross-polarised data improves the discrimination between surface scattering and volume scattering. Smooth surfaces, such as bare soils or areas with low vegetation appear in green tones (dominant HH backscattering) while vegetated areas appear in orange tones due to high HV backscattering associated to volume scattering. The pattern of eddies observed in orange tones from centre to right in the image corresponds to numerous meander bends covered by vegetation (high HV backscattering) on the Volga's floodplain. The Volga-Don Canal can be seen in blue colour flowing to the west from the south part of Stalingrad.

Technical Information:
Instrument: Advanced Synthetic Aperture Radar (ASAR)
Date of Acquisition: 16 April 2003
Orbit number: 05886
Orbit direction: Descending
ASAR Features: Alternative Polarisation Precision (30 meter resolution)
ASAR Mode: Image Swath 6 (70,1 km wide)
ASAR Polarisation: R=HV, G=HH, B=HV/HH

Credits: ESA 2003

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The eastern region of the South African peninsula can be seen clearly here on this Medium Resolution Imaging Spectrometer (MERIS) image. In the southwest the mountains of Western Cape can be seen extending eastwards to the coastal cities of Port Elizabeth, which can just be seen through the clouds, and Durban. To the north is the state of Pretoria and the city of Johannesburg. July is winter in the southern hemisphere and snow can be seen on the mountains of Lesotho. In contrast are the yellow sands of the Kalahari Desert in the northwest of the image.

MERIS was originally designed for ocean-colour monitoring but the outstanding radiometric quality of its five cameras enables land observations as well. The MERIS Global Vegetation Index, an ESA-derived product, has been developed in order to identify and distinguish the various types of vegetation and forests on regional scales. It should be of great help to those involved in research fields such as: deforestation monitoring, forest inventory and carbon cycle related issues. It will be soon delivered to users all over the world together with the many other geophysical products focusing on key parameters of our biosphere. Ocean, land and atmosphere will be studied by MERIS and its measurements will help us to better understand the climatic and environmental changes of our planet.

Technical Information:
Instrument: MEdium Resolution Imaging Spectrometer (MERIS)
Date of Acquisition: 6 July 2002
Orbit number: 01821
Instrument features: Reduced Resolution image (1200-meter resolution)

Credits: ESA 2002

Why are wetlands so valuable?

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Wetlands are an important ecological resource under threat

New guide highlights ESA’s environmental enforcement activities