@InProceedings{AzevedoTachSilv:2015:AvReEf,
               author = "Azevedo, Samara Cal{\c{c}}ado de and Tachibana, Vilma Mayumi and 
                         Silva, Erivaldo Ant{\^o}nio da",
                title = "Avalia{\c{c}}{\~a}o da redu{\c{c}}{\~a}o do efeito de 
                         sombreamento em imagens multiespectrais de {\'a}reas urbanas 
                         utilizando componentes principais e an{\'a}lise de agrupamento",
            booktitle = "Anais...",
                 year = "2015",
               editor = "Gherardi, Douglas Francisco Marcolino and Arag{\~a}o, Luiz 
                         Eduardo Oliveira e Cruz de",
                pages = "3707--3714",
         organization = "Simp{\'o}sio Brasileiro de Sensoriamento Remoto, 17. (SBSR)",
            publisher = "Instituto Nacional de Pesquisas Espaciais (INPE)",
              address = "S{\~a}o Jos{\'e} dos Campos",
             abstract = "Shadows represent a problem for feature extraction in urban areas, 
                         mainly when dealing with high spatial resolution remote sensing 
                         images. This work aims to evaluate one proposed method to remove 
                         shadow effects in multispectral images. Two approaches have been 
                         followed and compared. First, each band was corrected individually 
                         and principal components analysis (PCA) used to reduce high 
                         correlation that exists among images and the quantity to be 
                         processed. In the second approach, the PCA was firstly applied and 
                         corrected after, in order to verify the correction behavior in 
                         transformed data. To alleviate the shadow effects, priori 
                         detection of shadow areas using black top-hat morphological 
                         operator and automatic binarization were done, and then, these 
                         areas were corrected by local histogram matching from 
                         neighborhoods statistics. The method was tested in WorldView-2 
                         multispectral images from S{\~a}o Paulo city, which is one of the 
                         densest urban areas in the world. Experimental results and visual 
                         analysis have shown a decrease in radiometric differences caused 
                         by shadows in both approaches. Also, an increase on distinction 
                         between features that were occluded was observed and proven by 
                         unsupervised classification using k-media. However, further 
                         analysis and references data are necessary to guarantee that the 
                         radiometric value encountered corresponds that associated land 
                         cover. This study can contribute in the future with many 
                         applications such as 3D reconstruction, image matching, object 
                         recognition, etc.",
  conference-location = "Jo{\~a}o Pessoa",
      conference-year = "25-29 abr. 2015",
                 isbn = "978-85-17-0076-8",
                label = "729",
             language = "pt",
         organisation = "Instituto Nacional de Pesquisas Espaciais (INPE)",
                  ibi = "8JMKD3MGP6W34M/3JM4C2F",
                  url = "http://urlib.net/ibi/8JMKD3MGP6W34M/3JM4C2F",
           targetfile = "p0729.pdf",
                 type = "Processamento de imagens",
        urlaccessdate = "2024, Apr. 29"
}