TREES Project

ERS-1 SAR Mosaic

Context and realization

This mosaic of ERS-1 SAR (Synthetic Aperture Radar) images was obtained by assembling 477 individual images acquired between July 20 and August 28, 1994. This product presents a synoptic view of the vegetation and geology of Central Africa in a display never achieved before.
Because of permanent cloud cover the acquisition of earth observation satellite data over this tropical region has notoriously been difficult before the advent of satellite radar remote sensing.

The mosaic was assembled in the framework of the EC-JRC / ESA-TREES project. The objective of TREES is to develop an operational observation system for the regular monitoring of forest cover at the level of the whole tropical belt.

A mobile receiving station installed and operated at Libreville (Gabon) by the German Aerospace Agency (DLR) has acquired the ERS-1 SAR data set. About 3,000,000 km˛ have been covered during this short 1994 acquisition campaign.
The raw SAR data have been processed by the German Processing and Archiving Facility (PAF) into standard ERS-1 PRI products. A special purpose mosaicking software was developed at the Joint Research Centre to produce images in a geographic projection with a pixel spacing of 0.001 degree (±100 meters). All the full resolution images (477 images- 52 gigabytes) are kept in a data base at the JRC and are used in more detailed analyses.

Results

A full description of this mosaic and of its preliminary interpretation can be found in :

The information contained in this data set is highly valuable for the study of the forest cover of Africa. The limits between the rainforest domain and the savanna in the northern and in the southern part of the Congo basin are particularly well marked by a clear contrast between the radar signal over the two biomes, as illustrated in the two images presented here. Note that the south is seen here in the dry season while the north is in the middle of the rainy season.
Openings in the forest itself are visible when occupied by savanna. Large areas of secondary forest regrowth can be discerned along roads and old settlement areas.

North...

and South...

These two links are now under construction... They will soon enable you to see high resolution radar scenes of the forest-non forest contact zone !!!

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Credits and Contacts at the JRC

This work has been conducted under the supervision of Jean-Paul Malingreau, Franco de Grandi and MArc Leysen at the Monitoring of Tropical Vegetation Unit, Institute of Remote Sensing Applications, Joint Research Centre of the European Comission.

Many people have contributed to the preparation and analysis of this satellite data sets :

    Additional information can be obtained from G. De Grandi :
    Fax : +39 332 789073 ; E-mail : gianfranco.degrandi@jrc.it