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Studies from INPE indicate that the Amazon River is 140km longer than the Nile

Tuesday, July 01, 2008

The Brazilian National Institute for Space Research (INPE) completed the measurements of the lengths of the Amazon and the Nile using satellite images.According to a new methodology strongly supported by Remote Sensing and GIS the Amazon has 6,992,15 km whereas the length of the Nile is 6,852.06. The measurements confirm that the Amazon is the longest river in the world. The work was coordinated by Paulo Roberto Martini, from INPEs Remote Sensing Department.

Since the early nineties INPE has been studying the Amazon River through remote sensing and geoprocessing technologies developed within the Brazilian Space Programme . For these specific studies were used Geocover ortho-rectified mosaics and MODIS-NASA images as well. The interpretation was made by a specialist directly upon the digital image displayed by SPRING which is the freeware-GIS developed by INPE.

The Amazon measurements were taken upon Modis images (spatial resolution of 250 meters) and Geocover Mosaics (25 meters resolution) following its longer channels. The difference between the measurements were less than a pixel of the Modis or 250 meters in 6992,15 km. These results indicate that for long distances the measurements obtained with images of 250 meters of resolution and scenes with 25 meters lay within an acceptable error. According to the coordinator these results were achieved because the experience of the specialist was incorporated in the interpretation of the meanders of the Amazon. It was not only computing says Martini.

The farthest Amazon creeks where the measurements started were scientifically defined by an expedition to the sources of the river organized by RW Cine, in June, 2007. The expedition gathered researchers from Peruvian National Geographic Institute, the Brazilian National Water Agency (ANA), the Brazilian Institute of Geography and Statistic (IBGE) and INPE as well. According to Martini, an important support to collect cartographic and ecologic data by the expedition was provided by the use of CBERS (China Brazil Earth Resources Satellite)-CCD images and the Google Platform. They served as a database to orient the expedition and were integrated by Oton Barros, the researcher who was the representative of INPE in the mission.

The sources of the Nile was depicted from linemaps published elsewhere by traditional agencies such as US-National Geographic and the Encyclopaedia Britannica. The vector of the upwaters of the Nile ran from Victoria Falls crossing the Victoria Lake and followed the Kagera River reaching the farthest creek in the high peaks that separate Burundi from Rwanda.

The stuff of the methodology as the images, the software and the technical procedures does not require that experience and is easy to implement. So it can be applied for any big river of the planet covered by Modis sensing and even by the 250 meters resolution of CBERS-WFI Camera.

An article describing the procedures applied to the Amazon and the Nile heading Method to measure the lengths of the Amazon and Nile based on Modis and Geocover mosaics written by Paulo Roberto Martini, Valdete Duarte, Egdio Arai, from INPE, and Janary Alves de Moraes (AMBI) will be presented next September at the XIII Latin American Remote Sensing Symposium, in Havana de Cuba.


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