Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 16 de 16
Filtrar
Mais filtros











Intervalo de ano de publicação
1.
Appl Spectrosc ; 78(6): 567-578, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38465603

RESUMO

Given the growing urge for plastic management and regulation in the world, recent studies have investigated the problem of plastic material identification for correct classification and disposal. Recent works have shown the potential of machine learning techniques for successful microplastics classification using Raman signals. Classification techniques from the machine learning area allow the identification of the type of microplastic from optical signals based on Raman spectroscopy. In this paper, we investigate the impact of high-frequency noise on the performance of related classification tasks. It is well-known that classification based on Raman is highly dependent on peak visibility, but it is also known that signal smoothing is a common step in the pre-processing of the measured signals. This raises a potential trade-off between high-frequency noise and peak preservation that depends on user-defined parameters. The results obtained in this work suggest that a linear discriminant analysis model cannot generalize properly in the presence of noisy signals, whereas an error-correcting output codes model is better suited to account for inherent noise. Moreover, principal components analysis (PCA) can become a must-do step for robust classification models, given its simplicity and natural smoothing capabilities. Our study on the high-frequency noise, the possible trade-off between pre-processing the high-frequency noise and the peak visibility, and the use of PCA as a noise reduction technique in addition to its dimensionality reduction functionality are the fundamental aspects of this work.

2.
Rev. peru. biol. (Impr.) ; 30(4)oct. 2023.
Artigo em Espanhol | LILACS-Express | LILACS | ID: biblio-1530336

RESUMO

El cambio en el uso del suelo es uno de los principales conductores del cambio global, así como una causa de la pérdida de biodiversidad. En el norte del Ecuador, el matorral seco montano es un ecosistema característico de los valles interandinos y que se encuentra amenazado por la intervención antrópica. El presente trabajo estudió el cambio de la cobertura del matorral seco montano en el valle del río Chota en un periodo de 30 años y evaluó su estado de conservación. Se aplicó el método de clasificación supervisada en las imágenes satelitales LANDSAT de los años 1990, 2007 y 2020, para analizar las tasas de variación de las coberturas. El estado de conservación se determinó con una matriz de evaluación que consideró siete variables y 25 indicadores y la sobreposición de capas temáticas con SIG. Los resultados denotaron una pérdida del 20% de la cobertura del matorral seco montano, a un promedio anual de 231.83 ha/año (-0.75%) por causas antrópicas. Estas causas fueron responsables del cambio de cobertura de más de la mitad del 8.34% del área que ocupaba, principalmente la expansión de la frontera agrícola con un 3.96%. La presión y efecto de los factores antrópicos identificados causaron que el estado actual de conservación sea Regular. Se proponen tres estrategias de conservación: buenas prácticas agroecológicas, una gestión ambiental integral y la educación ambiental.


Land use change is one of the main drivers of global change, as well as a cause of biodiversity loss. In northern Ecuador, the montane dry scrub is a characteristic ecosystem of the inter-Andean valleys and is threatened by anthropogenic intervention. This study examined the change in montane dry scrub coverage in the Chota River Valley over a 30-year period and evaluated its conservation status. The supervised classification method was applied to LANDSAT satellite images from 1990, 2007, and 2020 to analyze the rates of coverage variation. The conservation status was determined using an evaluation matrix that considered seven variables and 25 indicators and the overlap of thematic layers with GIS. The results showed a loss of 20% of montane dry scrub coverage, at an annual average of 231.83 ha/year (-0.75%) due to anthropogenic causes. These causes were responsible for the coverage change of more than half of the 8.34% of the area it occupied, mainly the expansion of the agricultural frontier with 3.96%. The pressure and effect of the identified anthropogenic factors caused the current conservation status to be Regular. Three conservation strategies are proposed: good agroecological practices, comprehensive environmental management, and environmental education.

3.
Stat Med ; 42(27): 4952-4971, 2023 11 30.
Artigo em Inglês | MEDLINE | ID: mdl-37668286

RESUMO

In this work, we propose an extension of a semiparametric nonlinear mixed-effects model for longitudinal data that incorporates more flexibility with penalized splines (P-splines) as smooth terms. The novelty of the proposed approach consists of the formulation of the model within the stochastic approximation version of the EM algorithm for maximum likelihood, the so-called SAEM algorithm. The proposed approach takes advantage of the formulation of a P-spline as a mixed-effects model and the use of the computational advantages of the existing software for the SAEM algorithm for the estimation of the random effects and the variance components. Additionally, we developed a supervised classification method for these non-linear mixed models using an adaptive importance sampling scheme. To illustrate our proposal, we consider two studies on pregnant women where two biomarkers are used as indicators of changes during pregnancy. In both studies, information about the women's pregnancy outcomes is known. Our proposal provides a unified framework for the classification of longitudinal profiles that may have important implications for the early detection and monitoring of pregnancy-related changes and contribute to improved maternal and fetal health outcomes. We show that the proposed models improve the analysis of this type of data compared to previous studies. These improvements are reflected both in the fit of the models and in the classification of the groups.


Assuntos
Algoritmos , Software , Feminino , Humanos , Gravidez , Resultado da Gravidez , Modelos Estatísticos , Estudos Longitudinais
4.
Ciênc. rural (Online) ; 53(2): 1-9, 2023. mapas, tab
Artigo em Inglês | VETINDEX | ID: biblio-1410723

RESUMO

The extension of the area occupied by the inter tussock stratum and tussock stratum in natural pastures is essential for the productive performance of grazing animals. Images obtained from unmanned remote sensors can provide useful information, especially because they have a high spatial resolution. Thus, this study evaluated the performance of the supervised adaptive classification applied to aerial images obtained from an onboard drone camera to map the area covered by tussocks in a natural pasture of the Pampa biome. The study was carried out in a natural pasture area managed since 1986 under different forage allowances, considering treatments of 8, 12, and 16 kg of dry matter per 100 kg live weight (% LW). An aerial image from September 2017, obtained with a Canon S100 camera onboard a drone at an altitude of 120 m, with a spatial resolution of 5 cm, was used. The random forest and support vector machine classifiers were tested associated with specific classification rules. False-color images showed considerable visual similarity in the large patterns of the vegetation distribution and the validation performed with independent samples when compared to the classified images. The tested classifiers were able to measure the area covered by the tussock stratum, which could be an indicator of the quality vegetation in a natural grassland of the Pampa biome.


A quantidade de área ocupada por estrato inferior e superior em pastagens naturais tem grande importância sobre o desempenho produtivo dos animais em pastejo. Imagens obtidas de sensores remotos não tripulados podem fornecer informações úteis, especialmente por possuírem alta resolução espacial. O objetivo deste trabalho foi avaliar o desempenho de classificação supervisionada adaptativa aplicada a imagem aérea obtida por câmera a bordo de drone, no mapeamento da área coberta por touceiras em pastagem natural do bioma Pampa. O estudo foi realizado em área de pastagem natural, manejada desde 1986 sob diferentes ofertas de forragem, tendo sido considerados os tratamentos 8, 12 e 16 kg de matéria seca por 100 kg de peso vivo (% PV). Foi utilizada uma imagem aérea, de setembro de 2017, obtida com uma câmera Canon S100, a bordo de um drone a 120 m de altitude, correspondendo a resolução espacial de 5 cm. Foram testados dois classificadores, Random Forest e Support Vector Machine associados a regras específicas de classificação. As imagens de falsa cor, quando comparadas às imagens classificadas, apresentaram considerável semelhança visual nos grandes padrões de distribuição da vegetação, bem como na validação feita com amostras independentes. Os classificadores testados foram capazes de mensurar a área coberta por estrato superior, podendo ser um indicador da qualidade da vegetação, em pastagem natural do bioma Pampa.


Assuntos
Pastagens , Classificação , Sensores Remotos , Dispositivos Aéreos não Tripulados
5.
Ciênc. rural (Online) ; 53(2): e20210765, 2023. tab, graf
Artigo em Inglês | LILACS-Express | VETINDEX | ID: biblio-1375174

RESUMO

ABSTRACT: The extension of the area occupied by the inter tussock stratum and tussock stratum in natural pastures is essential for the productive performance of grazing animals. Images obtained from unmanned remote sensors can provide useful information, especially because they have a high spatial resolution. Thus, this study evaluated the performance of the supervised adaptive classification applied to aerial images obtained from an onboard drone camera to map the area covered by tussocks in a natural pasture of the Pampa biome. The study was carried out in a natural pasture area managed since 1986 under different forage allowances, considering treatments of 8, 12, and 16 kg of dry matter per 100 kg live weight (% LW). An aerial image from September 2017, obtained with a Canon S100 camera onboard a drone at an altitude of 120 m, with a spatial resolution of 5 cm, was used. The random forest and support vector machine classifiers were tested associated with specific classification rules. False-color images showed considerable visual similarity in the large patterns of the vegetation distribution and the validation performed with independent samples when compared to the classified images. The tested classifiers were able to measure the area covered by the tussock stratum, which could be an indicator of the quality vegetation in a natural grassland of the Pampa biome.


RESUMO: A quantidade de área ocupada por estrato inferior e superior em pastagens naturais tem grande importância sobre o desempenho produtivo dos animais em pastejo. Imagens obtidas de sensores remotos não tripulados podem fornecer informações úteis, especialmente por possuírem alta resolução espacial. O objetivo deste trabalho foi avaliar o desempenho de classificação supervisionada adaptativa aplicada a imagem aérea obtida por câmera a bordo de drone, no mapeamento da área coberta por touceiras em pastagem natural do bioma Pampa. O estudo foi realizado em área de pastagem natural, manejada desde 1986 sob diferentes ofertas de forragem, tendo sido considerados os tratamentos 8, 12 e 16 kg de matéria seca por 100 kg de peso vivo (% PV). Foi utilizada uma imagem aérea, de setembro de 2017, obtida com uma câmera Canon S100, a bordo de um drone a 120 m de altitude, correspondendo a resolução espacial de 5 cm. Foram testados dois classificadores, Random Forest e Support Vector Machine associados a regras específicas de classificação. As imagens de falsa cor, quando comparadas às imagens classificadas, apresentaram considerável semelhança visual nos grandes padrões de distribuição da vegetação, bem como na validação feita com amostras independentes. Os classificadores testados foram capazes de mensurar a área coberta por estrato superior, podendo ser um indicador da qualidade da vegetação, em pastagem natural do bioma Pampa.

6.
Spectrochim Acta A Mol Biomol Spectrosc ; 270: 120821, 2022 Apr 05.
Artigo em Inglês | MEDLINE | ID: mdl-35007903

RESUMO

Although cachaça and rum are distilled beverages obtained from the same raw material, they present differences in their chemical compositions. In this study, synchronous fluorescence spectroscopy was used combined with supervised classification models based on the partial least squares discriminant analysis to develop a rapid and low-cost model for discriminating between 50 cachaça and 40 rum samples. Partial least squares discriminant analysis models were constructed using synchronous fluorescence spectra recorded at wavelength differences of 10-100 nm. Initially, spectra were preprocessed by the first derivative with the Savitzky-Golay smoothing, and filter width and polynomial order were selected through face-centered central composite designs. For the construction and validation models, the spectra data were split into two datasets: the training and the test sets containing 60 (C, n = 33; R, n = 27) and 30 (C, n = 17; R, n = 13) samples, respectively. The best discrimination was achieved using fluorescence spectra recorded at wavelength difference 10 nm, allowing the discrimination of cachaça and rum with a classification efficiency of 98%. These results indicate that synchronous fluorescence spectroscopy offers a promising approach for the authentication of cachaças and rums.


Assuntos
Bebidas Alcoólicas , Bebidas Alcoólicas/análise , Análise Discriminante , Análise dos Mínimos Quadrados , Espectrometria de Fluorescência
7.
Eur J Investig Health Psychol Educ ; 11(3): 813-828, 2021 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-34563072

RESUMO

Almost 217 million secondary school students (60% of the world's adolescents) do not reach minimum levels in reading proficiency at the end of secondary school, according to objective 4.1 of the UN's Sustainable Development Goals. Therefore, the early and efficient identification of this disadvantage and implementation of remedial strategies is critical for economies. In 2018, the Programme for International Student Assessment (PISA) assessed the reading skills of 15-year-old students in 80 countries and economies. This work introduces a methodology that uses PISA's data to build logistic regression models to identify the main factors contributing to students' underperforming reading skills. Results showed that socioeconomic status (SES), metacognition strategies, Information and Communication Technology (ICT) skills, and student-teacher relationships are the most important contributors to low reading abilities.

8.
J Food Sci ; 85(12): 4194-4200, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33174205

RESUMO

Vegetables are important in economic, social, and nutritional matters in both the Brazilian and international scenes. Hence, some researches have been carried out in order to encourage the production and consumption of different species such as nonconventional vegetables. These vegetables have an added value because of their nutritional quality and nostalgic appeal due to the reintroduction of these species. For this reason, this article proposes the use of the machine learning technique in the construction of models for supervised classification and identification in an experiment with five leafy special of nonconventional vegetables (Tropaeolum majus, Rumex acetosa, Stachys byzantina, Lactuca cf. indica e Pereskia aculeata) assessing the characteristics of the macro and micro nutrients. In order to evaluate the classifiers' performance, the cross-validation procedure via Monte Carlo simulation was considered to confirm the model. In ten replications, the success and error rates were obtained, considering the false positive and false negative rates, sensibility, and accuracy of the classification method. Thus, it was concluded that the use of machine learning is viable because it allows the classification and identification of nonconventional vegetables using few nutritional attributes and obtaining a success rate of over 89% in most of the classifiers tested.


Assuntos
Aprendizado de Máquina , Valor Nutritivo , Verduras , Modelos Estatísticos , Folhas de Planta
9.
Heliyon ; 6(8): e04517, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32802974

RESUMO

Flooding in urban and periurban areas is a complex phenomenon that results from the interplay between urban expansion and the dynamics of the hydrological system. Understanding both processes is essential to manage flood risk. This study aimed to analyze the flood risk in urban and periurban areas of the upper and middle basin of the Luján River (Metropolitan Region of Buenos Aires, Argentina) between 1985 and 2015. We assessed the factors that affect flood frequency by analyzing the precipitation variations obtained from meteorological data and applying hydrological models. We also used supervised classification of remote sensing imagery to detect increases in impervious surface areas that could enhance flooding. Furthermore, we combined both analyses to identify flood risk situations in the region. Our results indicated that maximum precipitation and hydrometric values remained stable during the study period, with a marked interannual variability due to the presence of dry and wet phases. During the dry phase (2011-2015), when flooding events were infrequent, there was a steady urban sprawl in the floodplain area and, as a result, more people would have subsequently become exposed to flood risk. Our results evidence the lack of regional policies to regulate the urban sprawl in flood risk regions.

10.
Sensors (Basel) ; 19(7)2019 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-30987130

RESUMO

Motivated by the importance of studying the relationship between habits of students and their academic performance, daily activities of undergraduate participants have been tracked with smartwatches and smartphones. Smartwatches collect data together with an Android application that interacts with the users who provide the labeling of their own activities. The tracked activities include eating, running, sleeping, classroom-session, exam, job, homework, transportation, watching TV-Series, and reading. The collected data were stored in a server for activity recognition with supervised machine learning algorithms. The methodology for the concept proof includes the extraction of features with the discrete wavelet transform from gyroscope and accelerometer signals to improve the classification accuracy. The results of activity recognition with Random Forest were satisfactory (86.9%) and support the relationship between smartwatch sensor signals and daily-living activities of students which opens the possibility for developing future experiments with automatic activity-labeling, and so forth to facilitate activity pattern recognition to propose a recommendation system to enhance the academic performance of each student.


Assuntos
Desempenho Acadêmico , Análise de Dados , Monitorização Fisiológica/tendências , Smartphone , Acelerometria/métodos , Algoritmos , Humanos , Aprendizado de Máquina , Estudantes , Máquina de Vetores de Suporte
11.
Food Chem ; 273: 144-150, 2019 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-30292360

RESUMO

This work developed an analytical method to differentiate conventional and omega-3 fat acids enriched eggs by Raman spectroscopy and multivariate supervised classification with Partial Least Squares Discriminant Analysis (PLS-DA). Forty samples of enriched eggs and forty samples of different types of common eggs from different batches were used to build the model. Firstly, gas chromatography was employed to analyze fatty acid profiles in egg samples. Raman spectra of the yolk extracts were recorded in the range from 3100 to 990 cm-1. PLS-DA model was able to correctly classify samples with nearly 100% success rate. This model was validated estimating appropriate figures of merit. Predictions uncertainties were also estimated by bootstrap resampling. The most discriminant Raman modes were identified based on VIP (variables importance in projection) scores. This method has potential to assist food industries and regulatory agencies for food quality control, allowing detecting frauds and enabling faster and reliable analyzes.


Assuntos
Ovos/análise , Ácidos Graxos Ômega-3/análise , Análise de Alimentos/métodos , Análise Espectral Raman/métodos , Cromatografia Gasosa , Análise Discriminante , Gema de Ovo/química , Qualidade dos Alimentos , Análise dos Mínimos Quadrados
12.
Neuroinformatics ; 17(1): 147-161, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30008070

RESUMO

The shape of a neuron can reveal interesting properties about its function. Therefore, morphological neuron characterization can contribute to a better understanding of how the brain works. However, one of the great challenges of neuroanatomy is the definition of morphological properties that can be used for categorizing neurons. This paper proposes a new methodology for neuron morphological analysis by considering different hierarchies of the dendritic tree for characterizing and categorizing neuronal cells. The methodology consists in using different strategies for decomposing the dendritic tree along its hierarchies, allowing the identification of relevant parts (possibly related to specific neuronal functions) for classification tasks. A set of more than 5000 neurons corresponding to 10 classes were examined with supervised classification algorithms based on this strategy. It was found that classification accuracies similar to those obtained by using whole neurons can be achieved by considering only parts of the neurons. Branches close to the soma were found to be particularly relevant for classification.


Assuntos
Algoritmos , Dendritos/ultraestrutura , Modelos Neurológicos , Neurônios/classificação , Neurônios/citologia , Animais , Simulação por Computador
13.
BMC Bioinformatics ; 19(1): 166, 2018 05 03.
Artigo em Inglês | MEDLINE | ID: mdl-29724166

RESUMO

BACKGROUND: The development of new ortholog detection algorithms and the improvement of existing ones are of major importance in functional genomics. We have previously introduced a successful supervised pairwise ortholog classification approach implemented in a big data platform that considered several pairwise protein features and the low ortholog pair ratios found between two annotated proteomes (Galpert, D et al., BioMed Research International, 2015). The supervised models were built and tested using a Saccharomycete yeast benchmark dataset proposed by Salichos and Rokas (2011). Despite several pairwise protein features being combined in a supervised big data approach; they all, to some extent were alignment-based features and the proposed algorithms were evaluated on a unique test set. Here, we aim to evaluate the impact of alignment-free features on the performance of supervised models implemented in the Spark big data platform for pairwise ortholog detection in several related yeast proteomes. RESULTS: The Spark Random Forest and Decision Trees with oversampling and undersampling techniques, and built with only alignment-based similarity measures or combined with several alignment-free pairwise protein features showed the highest classification performance for ortholog detection in three yeast proteome pairs. Although such supervised approaches outperformed traditional methods, there were no significant differences between the exclusive use of alignment-based similarity measures and their combination with alignment-free features, even within the twilight zone of the studied proteomes. Just when alignment-based and alignment-free features were combined in Spark Decision Trees with imbalance management, a higher success rate (98.71%) within the twilight zone could be achieved for a yeast proteome pair that underwent a whole genome duplication. The feature selection study showed that alignment-based features were top-ranked for the best classifiers while the runners-up were alignment-free features related to amino acid composition. CONCLUSIONS: The incorporation of alignment-free features in supervised big data models did not significantly improve ortholog detection in yeast proteomes regarding the classification qualities achieved with just alignment-based similarity measures. However, the similarity of their classification performance to that of traditional ortholog detection methods encourages the evaluation of other alignment-free protein pair descriptors in future research.


Assuntos
Algoritmos , Bases de Dados de Proteínas , Árvores de Decisões , Proteoma , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/metabolismo , Análise de Sequência de Proteína/métodos
14.
Sensors (Basel) ; 8(9): 6055-6076, 2008 Sep 26.
Artigo em Inglês | MEDLINE | ID: mdl-27873859

RESUMO

Veredas (palm swamps) are wetland complexes associated with the Brazilian savanna (cerrado) that often represent the only available source of water for the ecosystem during the dry months. Their extent and condition are mainly unknown and their cartography is an essential issue for their protection. This research article evaluates some of the fine resolution satellite data both in the radar (Radarsat-1) and optical domain (ASTER) for the delineation and characterization of veredas. Two separate approaches are evaluated. First, given the known potential of Radarsat-1 images for wetland inventories, the automatic delineation of veredas is tested using only Radarsat-1 data and a Markov random fields region-based segmentation. In this case, to increase performance, processing is limited to a buffer zone around the river network. Then, characterization of their type is attempted using traditional classification methods of ASTER optical data combined with Radarsat-1 data. The automatic classification of Radarsat data yielded results with an overall accuracy between 62 and 69%, that proved reliable enough for delineating wide and very humid veredas. Scenes from the wet season and with a smaller angle of incidence systematically yielded better results. For the classification of the main vegetation types, better results (overall success of 78.8%) were obtained by using only the visible and near infrared (VNIR) bands of the ASTER image. Radarsat data did not bring any improvement to these classification results. In fact, when using solely the Radarsat data from two different angle of incidence and two different dates, the classification results were low (50.8%) but remained powerful for delineating the permanently moist riparian forest portion of the veredas with an accuracy better than 75% in most cases. These results are considered good given the width of some types often less than 50 m wide compared with the resolution of the images (12.5 - 15 m). Comparing the classification results with the Radarsat-generated delineation allows an understanding of the relation between synthetic aperture radar (SAR) backscattering and vegetation types of the veredas.

15.
Acta amaz ; Acta amaz;28(1)1998.
Artigo em Português | LILACS-Express | LILACS, VETINDEX | ID: biblio-1454633

RESUMO

Land use mapping is essential for the understanding of global change processes, especially in regions which are experiencing great pressure for development such as the Amazon. Traditionally, these mappings have been done using visual interpretation techniques of satellite imagery, that provide satisfactory results but are time-consuming and highly cost. In this paper, a technique of image segmentation based on region growing algorithm, followed by a per-field non-supervised classification, is proposed. Thus, the thematic classification is based on a set of image elements (pixels), benefiting from contextinformation, therefore minimizing the limitations of the digital processing techniques based on single pixels (per-pixel classification). This approach was evaluated in a typical test site of the Amazon region located to the north of Manaus, AM, using both original Landsat Thematic Mapper images and their decomposition into endmembers such as green vegetation, wood material, shade and soil, named mixture image in this paper. The results were validated by a reference map obtained from proved visual interpretation techniques of satellite imagery and by field check and indicated that automatic classification is feasible to map land use in Amazonia. Statistics tests indicated that there was significant agreement between the automated digital classifications and the reference map (at 95% confidence level).


O mapeamento do uso da terra é fundamental para o entendimento dos processos de mudanças globais, especialmente em regiões como a Amazônia que estão sofrendo grande pressão de desenvolvimento. Tradicionalmente estes mapeamentos têm sido feitos utilizando técnicas de interpretação visual de imagens de satélites, que, embora de resultados satisfatórios, demandam muito tempo e alto custo. Neste trabalho é proposta uma técnica de segmentação da imagens com base em um algoritmo de crescimento de regiões, seguida de uma classificação não-supervisionada por regiões. Desta forma, a classificação temática se refere a um conjunto de elementos (pixels da imagem), beneficiando-se portanto da informação contextual e minimizando as limitações das técnicas de processamento digital baseadas em análise pontual (pixel-a-pixel). Esta técnica foi avaliada numa área típica da Amazônia, situada ao norte de Manaus, AM, utilizando imagens do sensor "Thematic Mapper" - TM do satélite Landsat, tanto na sua forma original quanto decomposta em elementos puros como vegetação verde, vegetação seca (madeira), sombra e solo, aqui denominada imagem misturas. Os resultados foram validados por um mapa de referência gerado a partir de técnicas consagradas de interpretação visual, com verificação de campo, e indicaram que a classificação automática é viável para o mapeamento de uso da terra na Amazônia. Testes estatísticos indicaram que houve concordância significativa entre as classificações automáticas digitais e o mapa de referência (em tomo de 95% de confiança).

16.
Acta amaz. ; 28(1)1998.
Artigo em Português | VETINDEX | ID: vti-449695

RESUMO

Land use mapping is essential for the understanding of global change processes, especially in regions which are experiencing great pressure for development such as the Amazon. Traditionally, these mappings have been done using visual interpretation techniques of satellite imagery, that provide satisfactory results but are time-consuming and highly cost. In this paper, a technique of image segmentation based on region growing algorithm, followed by a per-field non-supervised classification, is proposed. Thus, the thematic classification is based on a set of image elements (pixels), benefiting from contextinformation, therefore minimizing the limitations of the digital processing techniques based on single pixels (per-pixel classification). This approach was evaluated in a typical test site of the Amazon region located to the north of Manaus, AM, using both original Landsat Thematic Mapper images and their decomposition into endmembers such as green vegetation, wood material, shade and soil, named mixture image in this paper. The results were validated by a reference map obtained from proved visual interpretation techniques of satellite imagery and by field check and indicated that automatic classification is feasible to map land use in Amazonia. Statistics tests indicated that there was significant agreement between the automated digital classifications and the reference map (at 95% confidence level).


O mapeamento do uso da terra é fundamental para o entendimento dos processos de mudanças globais, especialmente em regiões como a Amazônia que estão sofrendo grande pressão de desenvolvimento. Tradicionalmente estes mapeamentos têm sido feitos utilizando técnicas de interpretação visual de imagens de satélites, que, embora de resultados satisfatórios, demandam muito tempo e alto custo. Neste trabalho é proposta uma técnica de segmentação da imagens com base em um algoritmo de crescimento de regiões, seguida de uma classificação não-supervisionada por regiões. Desta forma, a classificação temática se refere a um conjunto de elementos (pixels da imagem), beneficiando-se portanto da informação contextual e minimizando as limitações das técnicas de processamento digital baseadas em análise pontual (pixel-a-pixel). Esta técnica foi avaliada numa área típica da Amazônia, situada ao norte de Manaus, AM, utilizando imagens do sensor "Thematic Mapper" - TM do satélite Landsat, tanto na sua forma original quanto decomposta em elementos puros como vegetação verde, vegetação seca (madeira), sombra e solo, aqui denominada imagem misturas. Os resultados foram validados por um mapa de referência gerado a partir de técnicas consagradas de interpretação visual, com verificação de campo, e indicaram que a classificação automática é viável para o mapeamento de uso da terra na Amazônia. Testes estatísticos indicaram que houve concordância significativa entre as classificações automáticas digitais e o mapa de referência (em tomo de 95% de confiança).

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA