National Institute for Space Research
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Detecção de mudanças na Floresta Nacional do Tapajós através de imagem diferença e dados RADARSAT - 2
No full textLand cover changes occur practically all over the world and are caused not only by natural but also by anthropic factors, or a its combination. The analysis of these changes is presented as important information on regions of interest and can be accomplished through various change detection techniques, based mostly in remote sensing data. Despite the wide applicability of optical remote sensing data in change detection, the great sensitivity of this type of data to clouds presence limits its use, especially in tropical and sub-tropical regions where adverse weather conditions are extremely common. Thus, the use of microwave data, are less sensitive to these conditions, shown as an alternative for the detection of changes in these regions. This paper aims to demonstrate the capability of microwave data, RADARSAT - 2, obtained in the C band, in change detection processes. Therefore, two RADARSAT - 2 images are used with HH polarization, containing part of the Tapajós National Forest - PA and change detection technique based on image differencing.Pages: 8374-838
Comparação entre imagem com e sem correção atmosférica mediante o Image Quality Index
No full textThis paper aims to compare by Index quality index (IQI), the change in reflectance image of the Indian Resource Satellite LISS3, on 27 March 2012 in São Mateus do Sul - PR, with or without use of atmospheric correction method of DOS (Dark Object Subtraction). This method corrects the image without taking into account the absorption, thus correcting just dark pixels caused by shadows of clouds, topography and others. The atmospheric correction is performed by subtracting the values measured for the image as a whole, assuming a uniform spreading across the scene. In order to verify the change of image processing after the DOS method was performed the calculation of IQI, which calculates the change in correlation, distortion of brightness and contrast. The results obtained by IQI show that the average brightness is the most altered in most bands of the sensor, however the correlation coefficient and the average similarity achieved the maximum value, demonstrating that the images were not modified accordingly. Therefore, we concluded that the atmospheric correction using Dark Object Subtraction resulted in differences in the visual image, and IQI clearly confirmed the search result, mediating the production of graphs and numerical results of this comparison.Pages: 4563-456
Saldo diário de radiação estimado com dados MODIS em condições de céu claro: Primeiros resultados
No full textThe net radiation is the main component of the surface energy balance. Many studies have been developed to estimate the net radiation using data from the surface and the atmosphere provided by the MODIS sensor aboard the Terra and Aqua satellites. However, these data are sufficient to estimate the net radiation only at the instant of satellite overpass, while the larger interest of the net radiation is per daily values, for example, in agriculture for daily estimates of evapotranspiration. This work aims to estimate the daily net radiation in clear sky conditions, using only data derived from MODIS. On a planar projection, the curve described by the radiation intensity that reaches the surface at each instant between sunrise and sunset can be approximated by a parabolic or sinusoidal curve In this paper, it is presented a parabolic model to estimate the diurnal variation of net radiation using only the instantaneous net radiation estimated with satellite data. A radiative transfer model was used to adjust an operating method for calculating shortwave radiation. The performance of the proposed method was compared to surface irrigated measurements in Ceará state. The results presented a relative error, in the daily average net radiation, less than 6,7%.Pages: 416-42
Autocorrelação espacial no estudo das diferenças sociais no Rio de Janeiro: antigas zonas, novas fronteiras
No full textThe tools for spatial data analysis are important for evaluation of a large volume of data. In this study, was used the Moran's Spatial Index for the spatial correlation analysis of indicators of urban infrastructure and income in the county of Rio de Janeiro, using new variables suggested by IBGE in the 2010 Census, relating to paving, lighting, public afforestation, presence of ramps for wheelchairs and income of heads of households. The spatial correlation of the variables revealed a transforming space, which shows that the current Planning Areas (PA's) adopted by the city of Rio de Janeiro are not sufficient to guide government action. Several most significant groups indicate a tendency of space reorganization that responds very quickly to the changes that have been occurring in the city. Through significant maps elaborated, the analysis led to the conclusion that, although spaces have been treated as homogeneous, they hold many different aspects that must be taken into consideration in formulating new policies for land ordering. This is the case of the districts of Campo Grande, Recreio dos Bandeirantes and Barra de Guaratiba. The visualization by sector and by district allowed to refine the analyses by considering smaller areas and to highlight more internally homogeneous groups.Pages: 3841-384
Análise de Fragilidade Ambiental e variabilidade das chuvas - Estudo de caso de Igaratá-SP
No full textDifferent visions of environmental fragility has been proposed along the time. They considered different variables in order to use and avail the geographic inference to achieve a quantitative result. One of these variables might be precipitation, which has a dynamic behavior and varies the pattern according to each season. Most methodologies which include precipitation in the inference of the environmental fragility process a dynamic process like a static phenomenon. It was done to quantify a value which will permit the allow the calculation of the final products. In this way they considered precipitation a unique value that varies in magnitude due to its temporal variability along the year or the seasons or the annual mean amount of precipitation. This paper aims to identify and analyze the variability of the environmental fragility in the city of Igaratá, located in São Paulo, Brazil. To accomplish this we considered the spatial and temporal variability of rainfall along the months. To this we used values of a precipitations from a period of twenty years. The fragility was calculated through a Fuzzy approach and multicriteria techniques to decision support. Besides the precipitation, it was also considered parameters like slope, soil and land use and land cover. It was concluded that the variability of rainfall can modify the location and magnitude of environmental fragility.Pages: 4829-483
Detecção de mudanças suave a partir de imagens de fração
No full textAutomatic change detection is an important challenge in multitemporal remote sensing applications. Some studies have been demonstrated that fraction images can be useful for land cover change detection because the radiometric problems are minimized and the interpretation of changes in land cover is facilitated, since the fractions have a physical meaning. Furthermore, interpretations at the subpixel level are possible. Because the sampling training is not required, unsupervised techniques are often chosen for the generation of change maps without intervention of the analyst. This work presents a soft classification procedure for detecting changes between a pair of fraction images. The technique is applied after the generation of binary change maps by a hard classifier based on Mahalanobis distance. The hard algorithm requires multivariate normality assumption for the differences among fractions, but the soft one logistic regression assumes nothing about the probability distribution of variables, requiring the estimation of few parameters. The soft classification allows estimating the probability of each pixel belonging to the change class; these probabilities are used to create a gradual change map. This approach was tested using a pair of synthetic images and the results were analyzed in terms of Mean Square Error (MSE). The results indicate that the soft classification have produced better results than only using the hard algorithm.Pages: 8122-812
Mineração de Dados e Classificação Baseada em Objetos no Mapeamento dos Estados de Médio Prazo da Paisagem na Bacia Hidrográfica do Rio São João, RJ
No full textThe landscape's status is constituted by structure characteristics and the action of physical elements or components in a given time interval. Thus, the variation of the time scale along with the action of agents, external or internal to the system, may modify the landscape's status. Assessing the landscape's status is as a task of great significance for studies aimed at forest restoration, land use, ecological-economic zoning, among others. The watershed of the São João river (BHRSJ) is one of the areas of the state of Rio de Janeiro that presents this high dynamism, possessing a wide range of environments and ecosystems. The present study evaluates the status changes of medium term (seasonal) of the BHRSJ's landscape on a regional scale (1:100.000 cartographic scale) in the last 4 years, using Landsat 5 TM images and the softwares WEKA and Ecognition 7.0 for data mining and object-based classification, respectively. The results show that approximately 30% of the Basin's entire surface is constituted by landuses and landcovers that present more than one landscape's status over the year. Of these, the lowlands are predominant, covering a 402 km² area that represents 19% of the entire basin. It is further concluded that the use of data mining sped up the modeling process adopted for classification.Pages: 7770-777
Uso de séries temporais de imagens Landsat/TM para estudo do processo de degradação ambiental de áreas de várzeas no semiárido mineiro
No full textThe studies of the behavior of process of environmental degradation of different ecosystems are extremely complex. In recent years, satellite images have become a great ally in these types of study, since they have the advantage of allowing the joint analysis of different variables, especially when associated with the time series. In this perspective, the study aimed to analyze the behavior of the process of environmental degradation in areas of meadows, at the southern end of the basin of the Rio Urucuia, situated in the north of the state of Minas Gerais, from LANDSAT images-5/TM. Characterized by a transition region between biomes savanna and caatinga, areas of meadows suffer strong anthropogenic pressures that are promoting major disturbances and disfiguration of the entire ecosystem. For the analysis were studied images of months more dry (July and August) and rainy season (January to March) of the years 1984, 1991, 2001 and 2011 respectively. The areas of meadows have been identified and mapped and then there was a automatic segmentation and analysis of the NDVI (vegetation index difference of standard) to study the behavior of the environment. The results showed that during the period analyzed, these areas fell by around 9.61 times, mainly due to silting. From the NDVI realizes that the areas of soil exposed in the advanced stage of deterioration. The greatest period of degradation was observed between the decades of 1980 and 2010 with reduction in these areas around 88.29 %.Pages: 6596-660
Uso de SIG na Avaliação da Contaminação por Chumbo e Cobre no Canal do Cunha e no Oeste da Baía de Guanabara , Rio de Janeiro, RJ
No full textAs well as other subbasins of Guanabara Bay, the Canal do Cunha's sub-basin, located in the city of Rio de Janeiro, suffered a severe environmental degradation as from the 1950s due to the accelerated urban-industrial development. Having a fluvial dynamics changed - by deforestation, dredging, occupying valleys and corrections - the channel is responsible for the flow of effluents and sediments that contribute to environmental degradation and has direct influence on water quality aggravation indices in the western portion of the Guanabara Bay. This study intends to evaluate, through GIS techniques, the spatial distribution of the levels of lead (Pb) and copper (Cu) launched by domestic sewage and industrial effluents using data provided by six points monitoring State Environmental Institute (INEA) . The representation of distributions allowed us to observe the influence of seasonality and the concentration of suspended sediment concentrations of metals. This work integrates the Canal do Cunha's characterization project, developed by the Laboratory of Environmental Impacts and Sustainability (LIMA) Nuclear Engineering Institute (IEN).Pages: 7904-791
Estimativa da acurácia posicional de documentos cartográficos na Petrobras a partir do erro máximo provável inferido do erro médio quadrático e da respectiva variância propagada
No full textThis article is an addition to a Petrobras procedure that aims covering unexpected situations and is an option to update the corporative standard of cartographic products validation. The principal objective is adjusting the used solution proposed by Merchant (1982) and applied to Brazilian law by Galo and Camargo (1994). Vieira and Genro (2011) show some discussions about the mentioned standard and this procedure proposed here configures itself on an option to adjust and complement the current solution. Our inference allows us to estimate accuracies even existing biases, however a bias statistic test continues to be executed assuming itself as an additional tool that aims to be an alternative to improve results, if it possible. Some adjusting were made on Congalton and Green (2009) method with the objective of leveling parameters with Brazilian law. Basically, we implemented the horizontal standard deviation gotten from propagation of variance (Gemael, 1994) and classified accuracy based in the maximum acceptable error using accumulated t-Student distribution. An example shows the rise of the new statistic inference using a sampling that represents an uncovered situation by previous solution. Our conclusions validate the new method to be applied to Brazilian law with some considerations, but represent an effective manner to get the accuracy standard of cartographic documents.Pages: 2038-204