Análise de dados OLI/Landsat-8 e MSI/Sentinel-2 com diferentes níveis de processamento / Analysis of OLI / Landsat-8 and MSI / Sentinel-2 data with different levels of processing

O objetivo deste trabalho é realizar uma análise comparativa de dados espectrais Landsat-8 (sensor Operational Land Imager - OLI) e Sentinel-2 (sensor Multispectral Instrument - MSI) utilizando diferentes níveis de processamento: dados originais (sem pré-processamento), reflectância do topo da atmosfera (top of atmosphere - TOA) e reflectância de superfície. Para isso foram utilizadas as bandas espectrais do infravermelho MSI-B8, MSI-B8A e OLI-B5 e o índice de vegetação NDVI (Normalized Difference Vegetation Index) de ambos os sensores. A comparação de valores espectrais dos sensores OLI e MSI mostrou que há significativa diferença nos seus dados espectrais (infravermelho e NDVI) considerando os dados originais. No entanto, há redução nessa diferença com a aplicação das respectivas transformações e correções radiométricas para reflectância TOA e reflectância de superfície. Em termos de valores de reflectância no infravermelho e de valores de NDVI, pôde-se constatar que a banda MSI-B8A é mais similar a OLI-B5 que a MSI-B8

ANÁLISE ORIENTADA A OBJETO E DADOS ASTER/TERRA NA CLASSIFICAÇÃO DO RELEVO

The aim of this research is to develop an object-based methodology for semi-automatic mapping of relief units. The study area is the municipality of São José dos Campos, located in São Paulo State, Brazil. For this end, a multilevel hierarchical semantic network (meant for the storage and reproduction of expert knowledge) together with fuzzy logic and a set of multispectral, geomorphometric and textural variables were used. The geomorphometric and textural variables were extracted from a DEM, obtained from a stereo pair of ASTER/Terra images. The DEM altimetric accuracy was evaluated. The validation of the final relief units map was accomplished by means of object-based statistical indices derived from an error matrix, obtained by means of a comparison between the classified scene and a reference map. This reference map was produced from a visual interpretation of the stereoscopic images. Based on the obtained results, the object-based approach has shown to be a suitable method for relief units mapping. O objetivo desta pesquisa foi desenvolver uma metodologia semi-automatizada de mapeamento de unidades de relevo, que utiliza análise orientada a objeto (AOO). A área de estudo é o município de São José dos Campos (SP). Com esse intuito, utilizou-se uma rede semântica hierárquica multinível para representação do conhecimento do especialista/geomorfólogo, além de lógica nebulosa e um conjunto de variáveis multiespectrais, geomorfométricas e texturais. As variáveis geomorfométricas e texturais foram derivadas de MDE obtido de imagens estereoscópicas do sensor ASTER/Terra. A acurácia altimétrica desse MDE foi avaliada. A validação do mapa de unidades de relevo foi realizada, considerando os objetos (ou segmentos) por meio de estatísticas derivadas de uma matriz de erros, obtida da comparação com um mapa de referência gerado a partir da interpretação visual das imagens estereoscópicas. Com base nos resultados obtidos, concluiu-se que AOO é uma metodologia viável para a semi-automação de procedimentos relacionados ao mapeamento de unidades de relevo

Assessing the extent of flood-prone areas in a south-american megacity using different high resolution dtms

Current forecasts estimate that almost 68% of the global population will be living in urban centers by 2050. As a result, the increase in impermeable surface area can result in severe hydrological impacts, such as the increase in surface runoff and the frequency of floods and their magnitude. Thus, this work analyzes the performance of the hydrodynamic model HEC-RAS for assessing the extent of flood-prone areas, using two digital terrain models (DTM) with different spatial resolutions (5 and 0.50 m). Four different computing intervals (1, 15, 30, and 60 s) were adopted aiming to evaluate the simulations outputs performance. Additionally, reported data by the civil defense are used for calibration and validation. In general, the model showed to be a powerful tool in the identification of susceptible areas to urban flooding. The simulated results in this work provide crucial geographic information when identifying spots with the highest risk of flooding, which should receive priority attention during such events. The simulations with a spatial resolution of 5 m showed the flood maps with the largest coverage of the flooded points (278 points out of 286—97.20%), within the shortest computation times. We highlight that the more refined DTM derived from spatial images did not produce the best flood simulation compared to the DTM with a spatial resolution of 5 m derived from orthoimages

An Assessment of the Altimetric Information Derived from Spaceborne SAR (RADARSAT-1, SRTM3) and Optical (ASTER) Data for Cartographic Application in the Amazon Region

Difficulties in acquiring a complete aerial photography coverage on a regular basis in the Brazilian Amazon due to adverse environmental conditions affect the quality of the national topographic database. As a consequence, topographic information is still poor, and when available needs to be up-dated or re-mapped. In this research, altimetric information derived from RADARSAT-1 (Fine and Standard modes), SRTM3 (3 arcseconds) and ASTER (band 3N-3B) was evaluated for topographic mapping in two sites located in the region: Serra dos Carajás (mountainous relief) and Tapajós National Forest (flat terrain). The quality of the information produced from Digital Elevation Models (DEMs) was evaluated regarding field altimetric measurements. Precise topographic field information acquired from Differential Global Positioning System (DGPS) was used as Ground Control Points (GCPs) for the modeling of the stereoscopic DEMs (RADARSAT- 1, ASTER) and as Independent Check Points (ICPs) for the calculation of accuracies of the products. The accuracies were estimated by comparison of the DEMs values and real elevation values given by ICPs. The analysis was performed following two approaches: (1) the use of Root Mean Square Error (RMSE) for the overall classification of the DEMs considering the Brazilian Map Accuracy Standards (PEC) limits and, (2) calculations of trend analysis and accuracy based on a methodology that takes into account computed discrepancies and standard deviations. The investigation has shown that for flat relief, the altimetric accuracy of SRTM3 and Fine RADARSAT-1 DEMs fulfilled the PEC requirements for 1:100,000 A Class Map. However, for mountainous terrain, only the altimetry of SRTM3 and ASTER fulfilled these requirements. In addition, the performance of ASTER was slightly superior to SRTM3. However it is important to consider the difficulties in the acquisition of good stereo-pairs with optical data in the Amazon and the additional cost (GCPs) to produce ASTER DEMs. Despite showing systematic errors, the findings justify the usage of SRTM3 as a primary elevation source for semi-detailed topographic mapping in the region. It is suggested a combination of altimetry derived for SRTM3 and planimetry extracted from high-resolution SAR (ALOS/PALSAR, TerraSARX, RADARSAT-2) or if available optical data for semi-detailed topographic mapping programs in the Brazilian Amazon, where terrain information is seldom available or presents low quality

Assessment of radargrammetric DSMs from TerraSAR-X Stripmap images in a mountainous relief area of the Amazon region

The Brazilian Amazon is a vast territory with an enormous need for mapping and monitoring of renewable and non-renewable resources. Due to the adverse environmental condition (rain, cloud, dense vegetation) and difficult access, topographic information is still poor, and when available needs to be updated or re-mapped. In this paper, the feasibility of using Digital Surface Models (DSMs) extracted from TerraSAR-X Stripmap stereo-pair images for detailed topographic mapping was investigated for a mountainous area in the Carajás Mineral Province, located on the easternmost border of the Brazilian Amazon. The quality of the radargrammetric DSMs was evaluated regarding field altimetric measurements. Precise topographic field information acquired from a Global Positioning System (GPS) was used as Ground Control Points (GCPs) for the modeling of the stereoscopic DSMs and as Independent Check Points (ICPs) for the calculation of elevation accuracies. The analysis was performed following two ways: (1) the use of Root Mean Square Error (RMSE) and (2) calculations of systematic error (bias) and precision. The test for significant systematic error was based on the Students-t distribution and the test of precision was based on the Chi-squared distribution. The investigation has shown that the accuracy of the TerraSAR-X Stripmap DSMs met the requirements for 1:50,000 map (Class A) as requested by the Brazilian Standard for Cartographic Accuracy. Thus, the use of TerraSAR-X Stripmap images can be considered a promising alternative for detailed topographic mapping in similar environments of the Amazon region, where available topographic information is rare or presents low quality.Pages: 67-7

MAPEAMENTO GEOMORFOLÓGICO COM IMAGENS ESTEREOSCÓPICAS DIGITAIS DO SENSOR ASTER/TERRA MAPEAMENTO GEOMORFOLÓGICO COM IMAGENS ESTEREOSCÓPICAS DIGITAIS DO SENSOR ASTER/TERRA

Neste artigo avaliaram-se as potencialidades e as limitações das imagens estereoscópicas do sistema sensor ASTER/Terra no mapeamento geomorfológico do município de São José dos Campos - SP. Com este intuito, os autores utilizaram: I) uma abordagem fotogramétrica para o tratamento geométrico e orientação do par estereoscópico de imagens; II) estereo-correlação e cálculo automático de paralaxes, visando à extração automática de um modelo digital de elevação que forneceu as informações geomorfométricas; III) métodos estatísticos na análise da acurácia posicional dos dados de sensoriamento remoto e IV) interpretação visual para o mapeamento de unidades geomorfológicas em ambiente digital. O mapa geomorfológico compreendeu 14 classes, e por meio da análise estatística, foi possível concluir que o par estereoscópico é adequado para mapeamento geomorfológico na escala de 1:50.000, e também, que o modelo digital de elevação possui acurácia altimétrica compatível com a escala 1:100.000. Palavras-chave: morfografia, morfometria, ASTER/Terra, modelo digital de elevação

Comparative Analysis of the Rigorous and the Polynomial Function Models for the Cartographic Accuracy Assessment of IKONOS Orthoimages and DSMs

Digital terrain models have made the earth surface modelling available. With the use of interpolated samples and depending on their location, different digital models can be created. Digital elevation models (DEMs) are built upon basis of samples referring to points located on the terrain, while digital surface models (DSMs) account for the elevation of natural and artificial features located above ground. The sources for the acquisition of elevation data are manifold, and the selection of the most appropriate ones for a given study will always rely on the specific goals at issue. In this paper, a 1m stereo pair of IKONOS-2 images covering part of Mairiporã municipality, São Paulo State, was used. This article is firstly committed to evaluate the elevation accuracy of DSMs obtained from a stereo pair of IKONOS images and their rational polynomial coefficients (RPC), with different combinations of ground control points (GCPs), and secondly, to assess the planimetric (positional) accuracy of orthoimages generated from DSMs with better elevation accuracy. The DSMs were generated with five different sets of GCPs: 9, 12, 15, 18, and 21. Each DSM and orthoimage were evaluated based on the root mean square error, using 21 independent check points (ICPs) surveyed on field. The RPC method, which allows the generation of relative DEMs and is less dependent on GCPs, yielded better accuracy than Toutin´s model both in the orthoimages and in the DEMs and DSMs generation. Através das técnicas de modelagem digital do terreno, é possível modelar a superfície terrestre através de amostras. Essas amostras, após serem interpoladas, e de acordo com a localização, dão origem a diferentes tipos de modelos digitais. Quando a elevação da grade provém apenas de pontos localizados na superfície nua do terreno, tem-se um modelo digital de elevação; quando incorpora valores de elevação das feições naturais e artificiais situadas acima da superfície nua do terreno, tem-se um modelo digital de superfície. Neste trabalho, foram utilizadas imagens estereoscópicas do sensor a bordo do satélite IKONOS-2, com 1 metro de resolução espacial, que recobrem parte do município de Mairiporã SP. O objetivo deste trabalho é avaliar a acurácia vertical de modelos digitais de superfície, gerados a partir de um par estereoscópico de imagens IKONOS e respectivos coeficientes polinomiais racionais (RPC), e a acurácia posicional de ortoimagens geradas a partir dos modelos digitais de superfície com maior acurácia vertical. Os modelos digitais de superfície foram gerados com cinco diferentes combinações de pontos de controle: 9, 12, 15, 18 e 21. Cada modelo e ortoimagem foram avaliados através do erro médio quadrático, com base em 21 pontos de validação levantados em campo. A modelagem RPC apresentou maior acurácia em relação à de Toutin na geração dos modelos e ortoimagem, e ainda apresenta vantagens como possibilidade de geração de modelos relativos e menor dependência do uso de pontos de controle.Pages: 323-33

Ortorretificação e análise da qualidade geométrica de imagens HRC CBERS 2B para uma região montanhosa

In the original geometry of high-resolution images are embedded spatial displacement effects, derived from the relief and changes in attitude of the camera image. The orthorectification is one of the most effective ways to mitigate the imperfections of the geometry these images. These corrections are essential. The good geometric quality and planimetric accuracy allow images of high spatial resolution to be used as measurements maps of geographic location, distance, angle and area. Given the availability of high resolution images, freely distributed by INPE and its importance for practical applications in various areas, we chose to orthorectify HRC images CBERS 2B and analyze their geometric quality. In order to demonstrate that such images can meet the technical parameters established by Brazilian legislation, this study was applied in an area that provides mild, moderate and very steeprelief conditions.Pages: 2740-274