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.

Tags: Euphrates River Lake Assad Syria | | Leave a comment

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.

Tags: Aïr Mountains Haruj Lake Chad Sahara Desert Tibesti Mountains | | Leave a comment

April 26th, 2010 Category: Mosaics, Rivers

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.

Tags: Asia Ganges River Gangetic Plain Ghaghara River Himalayas India Sarayu River Uttar Pradesh | | Leave a comment

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

FAPAR Index - Source and Processed products

FAPAR - Source 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.

Tags: Chelys Envisat FAPAR GCOS Meris MGVI Processor Raw Data SRRS Vegetation Index | | Leave a comment

September 11th, 2009 Category: Mosaics

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.

Tags: Chelys Envisat Meris MOSRI SRRS Summer 2008 World Map | | Leave a comment

August 26th, 2009 Category: Image of the day, Mosaics

SAR-Sharpened Mosaic of Italy

SAR-sharpening of Sardinia

The main image here was realized by merging ASAR and MERIS orthorectified Mosaics of Italy, generated by Chelys MOSRI, using a technique we call “SAR-Sharpening” due to its similarity to a method known as PAN-Sharpening.

PAN-Sharpening merges high resolution panchromatic and lower resolution multispectral imagery to create a single high resolution color image. “SAR-Sharpening”, on the other hand, uses a radar image instead of a panchromatic one.

In this image, we maintained the resolution of the MERIS sensor (250m) while greatly enhancing the level of detail using an ASAR mosaic with a 75m resolution.

The animated imagery focusing on Sardinia shows the improvements made through the SAR-Sharpening technique. Due to its resolution, the original color MERIS image clearly has a level of detail inferior to that of the ASAR image.

However, after the processing, the contours of the Italian terrain can be seen in great detail.

ENVISAT Sensor Coverage

ASAR operates simultaneously with the other ENVISAT instruments. The image on the left shows the swath positioning of ASAR along with those of the other sensors.

Chelys is currently exploring the possibility of enhancing the capabilities of their SRRS (Satellite Rapid Response System) processors, enabling them to automatically generate SAR-Sharpened images for all zones in which ASAR and MERIS images overlap.

Tags: ASAR Envisat Italy Meris Mosaics MOSRI Orthorectification SAR-Sharpening Sardinia SRRS | | Comments (1)

August 25th, 2009 Category: Mosaics

ASAR IMM Mosaic of Italy (Draft Version)

ASAR IMM Mosaic of Italy (Final Version)

This image of Italy is an ASAR Image Mode Medium Resolution Mosaic created with products acquired between January and July 2009.

These source images were generated starting from ENVISAT/Asar products, using the Chelys Satellite Rapid Response System.

They were then projected, orthorectified (with a NASA Digital Elevation Model of 3 arcseconds of resolution) and merged in this mosaic by Chelys MOSRI, a real time mosaic generation system, at the original resolution of 75 meters (0.000833 degrees per pixel).

The entire mosaic was generated in less than 1 minute. This is the latest version of the ASAR processing algorithm used by MOSRI which eliminates the banding effect created by merging the various original images.

Tags: ASAR Envisat Italy Mosaics MOSRI Orthorectification SRRS | | Leave a comment

July 17th, 2009 Category: Image of the day, Mosaics

Mosaic of Italy - June/July 2009

This is a mosaic of Italy generated in real time using orthorectified ASAR images just a few seconds after product reception.

The mosaic is visualized using Google Earth and can be navigated using the features of that program; the image shown here is a screenshot of the GE interface.

The images here were captured over the last three weeks, in late June and early to mid-July. As more images are acquired over the next two weeks, the black spaces will be filled in.

Tags: ASAR Google Earth Italy Mosaic Orthorectification | | Leave a comment

March 4th, 2009 Category: Earth Observation, Mosaics

Two weeks ago, we published a Meris FR Mosaic of Italy. The large number of interested users has led us to publish the entire Mosaic of Central/Eastern Europe. Starting today and over the next few weeks we will update the Mosaic section and the present post as soon as a new country is inserted.

Tags: Albania Austria Bosnia Bulgaria Croatia Czech Republic Germany Hungary Italy Macedonia Meris Montenegro Mosaic MOSRI Poland Romania Serbia Slovenia SRRS Switzerland Ukraine | | Leave a comment