IBGE makes available on its website today, June 1st, 2015, mosaics of orthorectified images of Piauí and a group of 30 image maps of Tocantins. With a spatial resolution of 10 meters, the images which originated these products were obtained between 2009 and 2014 by the AVNIR-2 sensor of the ALOS satellite.

The orthomosaics of Piauí cover 99.8% of the state. The images of the remaining 0.2% presented a high percentage of clouds over the territory and, for that reason, were not used. In the future, in order to include that small portion of the state not photographed by the ANVIR-2, IBGE may use images from another sensor.

The individual orthorectified images of Piauí, made available in 2013 and 2014, and the sections at 1:100,000 (1 cm=1km) of the orthomosaics released today are in GeoTIFF format, to be used in SIG (Geographic Information Systems) and can be transferred from the IBGE website, at: ftp://geoftp.ibge.gov.br/imagens_do_territorio/imagens_corrigidas/ortomosaicos/bc100/

The 30 image maps of Tocantins (which corresponded to 23% of the state area) are also represented by a 1:100,000 scale and correspond to a type of cartographic representation formed by a mosaic of orthorectified satellite images, with geographic names and marginal information in accordance with the sheets of Systematic Land Mapping.

The corresponding orthomosaics, in GeoTIFF, were made available between 2012 and 2013. The image charts launched today, in PDF format, have geometric properties as a topographic sheet and are available on the IBGE website: :ftp://geoftp.ibge.gov.br/imagens_do_territorio/imagens_corrigidas/cartas_imagem/bc100/

Collection is part of the BC100 Project

The collection of images made available is part of the project 'Cartographic Base 1:100,000 (BC100),' which has been conceived to give the Brazilian society access to orthorectified images, orthomosaics and image charts of several Federation Units. The objective is to fulfill the demand for updated information compatible with the 1:100,000 (1cm=1km) scale of representation.

The orthorectified images are corrected in terms of existing geometric deformation, caused by different factors, such as the angle of image acquisition, the relief, the curve and rotation of the Earth. The mosaic formation process gathers a group of AVNIR-2 orthorectified scenes which are cut and assembled in order to cover all the area corresponding to one topographic sheet.

The orthomosaics are used to produce image maps, which provide an updated view of the territory, compatible with the pre-requisites os scale representation, and present the names of the most relevant geographic elements on them. Given the simplified features of this product, society can make use of the information in a faster way than when considering a complete topographic sheet.

The AVNIR-2 sensor produces images with a spatial resolution of 10 meters, in four regions of the electromagnetic spectrum, corresponding to blue, green, red and near infrared. The images used in the project were acquired between years 2006 and 2010, and most of them, in 2009 and 2010.