Estudo preliminar da anisotropia de superfícies observada através de imagens MODIS

This work has as main goal to investigate the effect of anisotropy of surface components, which was assessed with surface reflectance for different view angles. We analyzed the in-band bidirectional reflectance derived from MODIS multi-angle images and simulated by laboratorial measurements. The in-band bidirectional reflectance factors simulated (equivalent to the first seven spectral bands of MODIS sensor) from vegetated surface (grass, Batatais) were obtained with portable spectroradiometer FieldSpec \uae 3 in the Radiometry Laboratory (LARAD/INPE) and compared with surface reflectance from MOD09GA/MODIS product. Results show that vegetated surfaces reflectances obtained in laboratory and by satellites images exhibit an anisotropic behavior. In the laboratory, the preferential directions of reflection showed a strong dependence between the illumination, the view angle and the wavelength, however, we observed that view angles of the highest reflectances values observed for the vegetated region differ from those observed by the satellite images. This is probably due to different lighting conditions and the different architectures of the canopies, which have height (vertical structure), density (horizontal structure), layout, organization and arrangement of individuals very differents to the vegetated areas treated. Furthermore, the analysis of the view angle shows a strong anisotropy for the Cerrado stricto sensu, an intermediate anisotropy for the forest region (in general, both areas showed the highest in-band reflectances values in the view angle above of 50 degrees) and a small anisotropy to bare soil, with the largest variations of the reflectances observed at view angles greater than 45 degrees.Pages: 8970-897

Ferramenta QLMODIS para rápida visualização e seleção de produtos MODLAND

The importance of MODIS (Moderate Resolution Image Spectroradiometer) products have been presented by several works available in the literature. These works presented and discussed the high quality of the products derived from MODIS sensors such as: high geometric quality of its images, 36 spectral bands, coverage of terrestrial globe each 2 days, i.e., high temporal resolution and free downloaded, what has caused a significant increase on temporal rate of data volume for several applications and researches. These products are provided free of charge by NASA (National Aeronautics and Space Administration) in a systematic way, allowing to use them for several studies. However, the multiplicity of data types, data specifications and the different functions they were developed to feature require a clear understanding by potential users of the whole set in a systematic schedule. In this context, the main objective is to present the QLMODIS tool, an interface for data distribution developed to facilitate the users to choose the best image dates, or periods, to obtain MODLAND data, designed for the studies of terrestrial ecosystems, in a simple and rapid way, so speeding up the selection of the data layers properly designed for each application. The proposed tool will facilitate to select images for the users who already have defined their research objectives, as well as a support in the planning stage of hardwork main processing of environmental information. Therefore,the present description of QLMODIS tool will be very useful for several (and potential) users of MODLAND products.Pages: 8162-816

Análise dos produtos de NDVI dos sensores MODIS/Terra e VEGETATION/SPOT

This study aims to assess the Normalized Difference Vegetation Index (NDVI) estimated by Moderate Resolution Imaging Spectroradiometer (MODIS) aboard Terra Satellite and by VEGETATION sensor aboard Satellite pour l'Observation de la Terre (SPOT). The NDVI values of January 01, 2012 (rainy season in almost Brazil territory) and July 21, 2012 (dry season in central-western of Brazil) were used and a compatibilization was performed between MODIS and VEGETATION due to spatial and temporal differences, taking into consideration the acquisition geometry, the percentage of cloud cover, among others. Moreover, to evaluate the NDVI values we performed a random sampling of 100 points, weighted by the total area of each Brazilian biome. Thus, we sampled 49, 24, 13, 10, 2 and 2 points for the Amazon, Cerrado, Atlantic Forest, Caatinga, Pantanal and Pampa biomes, respectively. Initial results indicate that the main differences between NDVI products could be related to the algorithm used for removing pixels with cloud, since the image with the peak of clouds shows the highest differences in estimated values. The statistical analysis indicates a significant difference between the NDVI values estimated by VEGEGETATION/SPOT and by MODIS/Terra for the first 10 days of January 2012 (p> 0.05, t-student). During this period, the correlation between D10 and S10 NDVI products with MODIS data were approximately 67%. Also, in July 21, 2012, the products showed a good agreement between both data, with a correlation of approximately 90% (p> 0.05, t-student).Pages: 1480-148

Distribuição de produtos MODIS via interface web

MODIS Land products users are familiar with the laborious and time consuming tasks involved in downloading the MODIS GeoTIFF images. The present work describes a web application to easy these tasks and accelerate the process of image acquisition. The implementation in PHP with JAVA integration language presents a friendly environment to download the images at http://www.dsr.inpe.br/laf/modis. The users can specify the MODIS Land product of interest informing the spatial resolution, the composition (8 or 16 days), the time period (seasonal or interval), and the area of interest. The images should be available to the user few minutes after posting the request.Pages: 7502-750