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Archive for Mosaics

Irrigated Land Near Lake Assad, Syria

35.9N 38.2E

March 6th, 2011 Category: Mosaics, Rivers

Syria - February 11th, 2011

Lake Assad (dark blue, upper left quadrant) is a reservoir on the Euphrates River in Ar-Raqqah Governorate, Syria. It was created in 1974 when the Tabqa Dam was closed.

Lake Assad is Syria’s largest lake with a maximum capacity of 11.7 cubic kilometres (2.8 cu mi) and a maximum surface area of 610 square kilometres (240 sq mi).

A vast network of canals uses water from Lake Assad to irrigate lands on both sides of the Euphrates. Such lands appear greenish in this image (open full image for better detail) despite the surrounding arid terrain.

Sahara Desert Bordered by Mountains and Lakes in Libya, Chad and Niger – November 15th, 2010

22.9N 14.7E

November 15th, 2010 Category: Deserts, Image of the day, Lakes, Mosaics

Libya, Chad and Niger - October 27th, 2010

While the center part of this image is covered in yellow Sahara Desert sands, several other interesting geographical features can be observed by the edges.

The dark brown area in the upper right corner is the Tibesti Mountains, a group of mostly inactive volcanoes in northern Chad and extending a short distance into southern Libya.

Lighter brown in color and showing more circular patterns at the center left edge are the Aïr Mountains, in northern Niger, within the Sahara desert. The part of the Sahara east of the massifs is also known as the Ténéré Desert.

The green area by the bottom edge is Lake Chad, a shallow but large lake surrounded by wetlands in central Chad, on the edge of the Sahara Desert. In the full image, the yellow sands of the Sahara can be seen giving way to less arid lands to the south.

Finally, visible only at the top of the full image, is the Haruj volcanic field in central Libya. This large field contains many volcanoes, craters and lava flows.

Sarayu, Ghaghara and Ganges Rivers, Northern India

26.3N 86.0E

April 26th, 2010 Category: Mosaics, Rivers

India - March 5th, 2010

India - March 5th, 2010

Both the Ganges and Sarayu Rivers can be seen flowing across the Gangetic Plain, south of the Himalayas, in this image of northern India. The Sarayu, identifiable by its almost 90º turn to the east after flowing down from the Himalayas, crosses the state of Uttar Pradesh.

The Sarayu is often considered to be synonymous with the modern Ghaghara River or as a tributary of it. The Ghaghara, in turn is a left-bank tributary of the Ganges. The two rivers can be seen at their confluence halfway between the center and the right edge of the image.

New FAPAR/MGVI Raw Data Processor for Monitoring Vegetation Cover

October 2nd, 2009 Category: Climate Change, Earth Observation, Image of the day, Mosaics

FAPAR Index - Source and Processed products

FAPAR Index - Source and Processed products

FAPAR - Source Product

FAPAR - Source Product

FAPAR - Processed Product

FAPAR - Processed Product

Envisat’s Medium Resolution Imaging Spectrometer (MERIS) acquires multi-spectral imagery of the Earth, and is used to monitor the state and evolution of the terrestrial vegetation cover.

In particular, the MERIS Global Vegetation Index (MGVI), which corresponds to the Fraction of Absorbed Photosynthetically Active Radiation (FAPAR), is generated operationally as a standard level-2 product, using the radiation measured by MERIS over land surfaces.

This bio-geophysical product plays a critical role in the plant photosynthetic process and is regularly used in diagnostic and predictive models to compute the primary productivity of the vegetation canopies.

FAPAR has been established as a fundamental surface parameter by international organizations including the Global Climate Observing System (GCOS), charged with providing data on the Earth’s climate system.

Chelys has developed a new processor that is able to process and directly extract the FAPAR index from raw data (level-0) at a reduced or full resolution (but also from level-1), generating the relative false-colored image just a few seconds after the original data is ingested.

In the next few weeks, a processor that will systematically generate these vegetation index images will be incorporated in the SRRS (Satellite Rapid Response System). As soon as enough images have been collected, it will be possible to generate mosaics as well.

The World from MERIS – Summer 2008

September 11th, 2009 Category: Mosaics

The World from MERIS - Summer 2008

The World from MERIS - Summer 2008

Over 2000 Level0 Reduced Resolution products from the MERIS instrument onboard the Envisat satellite were collected in the time period from January to August 2008 and processed by the Chelys Satellite Rapid Response System (SRRS) to generate high quality images.
The images were projected to obtain this composite view using MOSRI, a real time mosaic generation system, which automatically removes clouds and shadows while combining the data.

The new mosaic is available at different resolutions in the MOSAICS section of the EOSnap website.