From this Tuesday (September 14th), users of mapping, cartography and natural resource evaluation services will have access to new satellite images of the "Legal Amazon" and of the Northeast region. The 2,100 images made available in the site of IBGE display a 20-meter resolution, are recent (obtained between April and September of 2008) and were orthorectified (their landscape deformations were corrected and geographical coordinates were included). The new orthorectified images cover 17 states, totaling an area of more than 6,300,000 km2, which correspond to approximately 74% of the national territory. They can be accessed at ftp://geoftp.ibge.gov.br/Alos.
The images were obtained by PALSAR (Phased Array L-band SAR), a Synthetic Aperture Radar (SAR) which operates within the L-band range. This kind of radar imager sensor is specially useful due to its capacity of generating images even in regions covered by clouds, which is a frequent situation in the North and Northeast regions of the country. Moreover, the images orthorectified by IBGE have a double polarization, what allows a better interpretation of the information contained in the images.
PALSAR is one of the sensors onboard the ALOS satellite, launched by the Japanese spatial agency (JAXA) in January of 2006.
Source: IBGE
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