National Institute for Space Research
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Sunglint removal in high spatial resolution hyperspectral images under different viewing geometries
No full textSunglint, also known as specular reflection of light from water surfaces into sensor optics, is a component of sensor-incoming radiance that represents a degrading factor on the spectral characterization of water bodies. Airborne remote sensors are suitable to evaluate and monitor freshwater ecosystems, unfortunately those sensors can be heavily affected by sunglint, due to their high spatial resolution. Although, sunglint effects can be minimized in airborne remote sensing by optimizing the viewing geometry, those conditions cannot always be applied, due to the size and spatial pattern of inland water bodies, so methods to identify and correct for extraneous radiance contributions are essential. The present study reviews current techniques to remove sunglint radiance component from high spatial resolution images and tests a deglint algorithm in a set of airborne hyperspectral images acquired under different viewing geometry. The results demonstrate the sunglint effects damaging the images, directly influencing its visual aspects, the magnitude of the image spectra under glint conditions and masking the correlations between the optically active substances and the spectral data. The algorithm applied showed good results removing the sunglint in the images, providing a viable solution to mitigate those effects in higher resolution hyperspectral images of optically complex waters, acquired by airborne sensors.Pages: 7958-796
Caracterização da refletância espectral de materiais urbanos com uso de espectroradiômetro
No full textThe purpose of this work is to identify the spectral behavior of the urban targets (asphalt, concrete, basalt, granite and road without pavement), with field reflectance measurements using a spectroradiometer (FieldSpec instrument) and to establish its relation with reference spectral library and vary works made about reflectance of urban targets and rocks mineralogy, used to develop a generalized knowledge base for analysis of different materials. The noise of Spectral reflectance measurements were smoothed using mean-filter smoothing algorithms. Derivative analysis algorithm was applied to enhance spectral features. Continuum-removal was applied by feature-extraction absorption bands. Results showed that urban materials are altered by manufacturing processes and the way they are combined. Urban materials can also be altered by coatings and urban spectra are further modified. Were identified typical spectral features can be associated with some minerals and iron oxides between 500 nm and 700 nm.Pages: 8893-890
Estudo da variabilidade de parâmetros físicos e biológicos estimados por satélite no Atlântico Sudoeste através de Análises Empíricas Ortogonais
No full textThis work studies the variability of the South Atlantic Ocean based on the multivariate methodology of the empirical orthogonal function applied to satellite derived chlorophyll concentration (CSM) and sea surface temperature (TSM) data. Those parameters are also analyzed relating its variability to the oceanographic processes, as boundary currents, westward propagating planetary waves and river discharges occurring into specific regions. Results are consistent with those already described in the literature. The strong seasonal cycle is confirmed in the analysis of non-normalized sea surface temperature and chlorophyll time-series and might mask lower signals. There are notable differences between the continental shelf and the offshore. The Rio da Prata and the Lagoa dos Patos seasonal signals are detected in the second EOF and are better characterized in the analysis of normalized time-series. In the analyses of normalized data, the anomalies indicate interannual variability, probably influenced by the occurrence of low periodicity levels known as Rossby waves. The semiannual periodicity found by spectral analysis suggests an influence of coastal discharges associated with local rainfall. The correlation between TSM and CSM data also reflects a strong relationship with physical driving processes, such as the South Atlantic Convergence Zone displacement, the general surface circulation and coastal discharges in some zones of the ocean.Pages: 7803-781
Análise temporal de desmatamento e passivos ambientais da bacia do rio Preto no Distrito Federal
No full textThe conversion of natural vegetations into crop fields due to the increasing demand of food production has turned the Cerrado into the new agricultural frontier in the country. In the Federal District, a major part of crop fields are located within the Rio Preto's watershed. Monitoring and detailed mapping projects of the land occupation have showed to be effective to support public policies and to improve land social justice and productivity. The use of GIS techniques and Remote Sensing make it possible to monitor land use and land cover change in rural areas. This study aimed to assess Unsupervised (Isodata) and Decision Tree classification techniques using images derived from Principal Component Analysis (PCA) to map land use/land cover changes and degradation of natural vegetation in the Rio Preto watershed between1990 to 2010. Based on this research results, it was estimated degraded areas delined as permanent protection by 2010. The Confusion Matrix results indicated that the best performance (81,7% of overall accuracy) was observed for non-supervised classification technique IsoData. This research results also showed that 41.1% of the Rio Preto Watershed had been deforested by 1990. The total deforestation area has increased 12,1% between 1990 and 2010, and the greatest deforestation increase (10,5%) was observed between 1990 and 2000. Additionally, it was estimated that 80% of the rural properties showed total or partial degradation of Permanent Protected Areas and 72% of those properties were considered illegal based on current environmental law.Pages: 6371-637
Avaliação da distribuição espacial do índice de área foliar em Floresta Estacional Decidual com base em fotografias hemisféricas
No full textBiophysical measures of forest are fundamental to quantify the commercial biomass, determine the carbon sinks, monitoring large vegetation areas. The objective of this work was to estimate forest canopy leaf area index in two plots located in the Universidade Federal de Santa Maria campus in Frederico Westphalen, using hemispherical photographs. The two plot of one hectare were systematic sampled with small plot of 20m by 20m, totalizing 25 samples in each hectare. The fish eye lent and the camera were leveled using a tripod and oriented to the magnetic North. The tripod was adjusted to the breast height diameter (BHD ~1.3m). Two photographs were acquired for each point, to allow a double processing. The hemispherical photographs were processed to calculate the leaf area index (LAI) based on the gap fraction of the canopy. After IAF calculation, the data were interpolated using linear kriging. The results showed an average IAF of 3.64 (\ub1 0.62) and 3.27 (0.66). The spatial approach showed that the main plots present internal variations. These variations can be associated to soil differences, water availability, slope, etc. These preliminary results suggest that hemispherical photographs can be used to quantify forest biophysical parameters such as LAI. More studies are necessary to validate the present results, based on long term data acquisitions.Pages: 3456-346
Utilização dos índices de vegetação EVI e NDVI como ferramenta de análise da dinâmica da vegetação no Parque Nacional da Serra da Canastra - MG
No full textThe advancement of space research facilitated access to images produced by satellites, often available for free. Such images facilitate studies whose geographic information obtained are applied in different areas such as agriculture, forest, meteorology, cartography and urban cadastre. In order to know about vegetation vigor many studies use Vegetation Indices (VIs). The VIs use surface reflectance at wavelengths designed to highlight a particular property of vegetation. The VIs correlated with precipitation revealed the time response of vegetation according precipitation in a particular area. The Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI) from MODIS and VEGETATION-2 sensors respectively, also rainfall data were used in this research to study changes in vegetation at Parque Nacional da Serra da Canastra, from 2008 to 2011 in the state of Minas Gerais. The Integrated Land and Water Information System (ILWIS) software was used to support, import, process and analyze the special information. The results showed that values of EVI were lower than the values of NDVI for the entire period of study. It was observed that NDVI had small values when the EVI reached peaks. Relative to rainfall, the NDVI had the highest response time. Some characteristics from the sensors also contributed for differences in the found values.Pages: 3282-328
Análise da confiabilidade dos dados MODIS e do seu potencial para a discriminação de cobertura de terras no Oeste da Bahia
No full textThis study was conducted in the western Bahia State with the aim to analyze the MODIS pixel reliability data and to analyze the potential of the MODIS EVI2 time series (2001-2010) to discriminate representative land use and land cover classes of the study area. We conducted a pixel-per-pixel based analysis of the reliability of entire temporal series. For the analysis of land use and land cover discrimination capability, the following classes were considered: shrub Cerrado (Campo Sujo), Cerrado shrubland (Cerrado Ralo, Cerrado Típico and Cerrado Denso), cropland, pastureland and reforestation. Representative samples of EVI2 values were collected for each class. The potential of discrimination capability was analyzed statistically through the cluster analysis. The cluster analysis included: a) time series of EVI2 itself; b) cumulative EVI2 (sum of individual EVI2 values one-by-one); c) cumulative, normalized EVI2 (EVI2 time series normalized by moving average and summed one-by-one). Overall, MODIS data set presented high reliability: 84% of data were rated as good. In terms of seasonality, 96% of dry-season data (April-September) and 69% of wet-season data (October-March) were rated as good. The analysis of time series of EVI2 (simple and cumulative) demonstrated that each land use and land cover class present overall distinct temporal signatures and that the cumulative EVI2 image has better discrimination capability than any other individual EVI2 image. Cluster analysis results indicated that the normalized and cumulative EVI2 data set presents the best capability to discriminate representative land use and land cover classes of the study area.Pages: 1634-164
Assinatura espectral do coral endêmico brasileiro Siderastrea stellata
No full textStudies involving spectroradiometry data are important as they provide a basis for interpreting remote sensing data at different levels, enabling better performance of mapping and environmental monitoring, in the case of marine environments beyond the need for knowledge of radiometry data is necessary remove the influence of the water column in orbital images. This paper aims to initiate studies of spectral signatures in Brazilian corals in order to close one gaps for possible realization of environmental monitoring of coral reefs through satellite sensors. In Brazil were not found studies about spectroradiometry of its corals, this is pioneering work. Chose to work with the species Siderastrea stellata to be a primary constructor of coral reefs, resist strongly to environmental variations and be endemic the Brazilian coast. Data were collected in aquariums at the headquarters of Projeto Coral Vivo in city of Arraial d'Ajuda, using the portable spectroradiometer FieldSpec\uae 3 Hi-Res, the signatures were analyzed using the software Envi 4.7. Corals have an unscheduled called tripled-peaked which define them as brown corals, and have marking belonging to chlorophyll pigment. It is observed that the features markers are obtained through the presence / absence of pigments of the tissue to coral or to algae zooxanthellae. By comparing the signature of this coral with other species of the same genus found in North America could observe differences that allow separate her. Thus obtains a signature pattern of the specie S. stellata.Pages: 7882-788
Análise Espacial dos Efeitos da Agropecuária e do Crédito Rural sobre o Bioma Cerrado
No full textThis work aimed to appoint the interactions between agriculture, livestock and rural credit on land use at state of Goiás using remote sensing and census data. The grasslands loses more of 85 % on your original cover between 1970 and 2006. The forestlands and shrublands have been recovering your cover, but in 2006 they lose too and more of 22 % on your original cover. The cultivation of sugar cane increases 5.133 % in three years, into 2002 and 2005. The agriculture rural credit destined for big farms not response for raise the croplands. Nevertheless, its not possible say the same in relation to livestock rural credit, because the data of Rural Credit National System dont have the level of information necessary to explain your relationship with increase of pasturelands. The comparing with rural financing amount show that for each R1,64 of agriculture credit.Pages: 6268-627
Mapeamento das Áreas de Reflorestamento no bioma Cerrado, com base em imagens LANDSAT 5 - TM: um estudo de caso para a Fronteira Agrícola no Oeste da Bahia, Brasil
No full textAccording to the 2006 agricultural census data (IBGE, 2006), there are in the Cerrado biome significant reforestation areas, especially in the Western region of Bahia state. In this context, and focusing in the historical dynamic reforestation process in Cerrado region, this research aimed to map and analyze the eucalyptus crop areas located at the municipalities of Jaborandi, Cocos and Correntina (Bahia), which represent one of the last agricultural frontiers in Brazil. For performing this analysis, we employed Landsat 5 TM imagery, covering the scenes 229/069, 229/070, 220/069 and 220/070, through the years 1990, 2000 and 2010, and visual technics of image interpretation to identify areas of existing reforestation. In a preliminary assessment, it was observed a large concentration of reforestation areas in 1990, with 1,009 km², followed by 902.2 km² in 2000, and 180.76 km² in 2010. Other studies are yet necessary, aiming to compare other eucalypt crop areas in Cerrado, as well as to understand and support new scenarios (actual and future) of possible reforestation areas in this biome.Pages: 2843-284