A Floresta Amazônica é a maior floresta tropical contígua do planeta e cobre cerca de 40% território brasileiro, vem passando por intenso processo de conversão de áreas florestais, principalmente, no arco do desmatamento que é uma área crítica com problemas ambientais como queimadas e desflorestamento. O município de Conceição do Araguaia-PA encontra-se nessa área crítica e apresenta-se como uma frente de expansão da atividade agropastoril na região. O objetivo do trabalho foi analisar temporalmente as mudanças de uso e cobertura da terra no município de Conceição do Araguaia. Para o desenvolvimento do trabalho foram utilizadas imagens do satélite Landsat-5/TM do ano de 1999 e 2009, e do satélite Landsat-8/OLI-TIRS do ano de 2019 processadas e classificadas na plataforma Google Earth Engine. A partir dos resultados obtidos constatou-se que entre os anos de 1999 e 2019 houve um desflorestamento de 22% no município em estudo, sendo que a atividade agropastoril obteve um aumentou de 14,6%. Com isto pode-se concluir que as condições edafoclimáticas favorecem o desenvolvimento da agropecuária e ela está diretamente ligada ao desflorestamento local, caracterizando-se como a principal matriz econômica do município.
The ionosphere may not only degrade the accuracy of the GNSS positioning but also reduce its availability because there is a high dependence between signal losses and ionospheric irregularities. Irregularities in the Earth's ionosphere may produce rapid fluctuations in phase and amplitude. These rapid fluctuations are called ionospheric scintillation. Thus, loss of signal can occur due to the effects of diffraction and refraction, which cause a weakening in the signal received by the GNSS receivers. In this way, this paper aims to evaluate the magnitude of ionospheric scintillation in Brazil and the performance of the positioning under its influence in the period of high solar activity in the current cycle (24), through the Spearman correlation analysis and the Wavelet periodogram. For that, three-year time series (2012 to 2014) of the S4 index and 3D MSE (Mean Squared Error) of three Brazilian stations with different ionospheric conditions were considered, PALM (near the Geomagnetic Equator) PRU2 (Equatorial region and Anomalies) and POAL (Mid-latitude region). Thus, it was possible to evaluate the correlation between the accuracy of the precise point positioning using only the C/A code of the GPS satellite and the S4 index. As a result, there was a correlation of 53% and 51%, using the Spearman method, for the PALM and PRU2 series, respectively. In addition, considering the analysis of space-frequency in relation to time by the Wavelet coherence method, a correlation of more than 70% is noted in the period of greatest 3D MSE concerning the spring and autumn equinox months.
Extração vetorial automática de corpos hídricos a partir de imagens orbitais, utilizando a linguagem python sobre o rio paranapanema Automatic vector extraction of water bodies from orbital images, using a language python on the paranapanema river
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