Identification of croplands of winter cereals in Rio Grande do Sul state, Brazil, through unsupervised classification of normalized difference vegetation index images

Abstract

This study aimed to propose methods to identify croplands cultivated with winter cereals in the northern region of Rio Grande do Sul State, Brazil. Thus, temporal profiles of Normalized Difference Vegetation Index (NDVI) from MODIS sensor, from April to December of the 2000 to 2008, were analyzed. Firstly, crop masks were elaborated by subtracting the minimum NDVI image (April to May) from the maximum NDVI image (June to October). Then, an unsupervised classification of NDVI images was carried out (Isodata), considering the crop mask areas. According to the results, crop masks allowed the identification of pixels with greatest green biomass variation. This variation might be associated or not with winter cereals areas established to grain production. The unsupervised classification generated classes in which NDVI temporal profiles were associated with water bodies, pastures, winter cereals for grain production and for soil cover. Temporal NDVI profiles of the class winter cereals for grain production were in agree with crop patterns in the region (developmental stage, management standard and sowing dates). Therefore, unsupervised classification based on crop masks allows distinguishing and monitoring winter cereal crops, which were similar in terms of morphology and phenology.

Uso de imagens do sensor orbital modis na estimação de datas do ciclo de desenvolvimento da cultura da soja para o estado do Paraná – Brasil

“…Embora pesquisas (AGUIAR et al, 2009;MERCANTE et al, 2009;JOHANN et al, 2012;RISSO et al, 2012;MERCANTE et al, 2012;JUNGES et al, 2013) tenham obtido relativo êxito na utilização de sensores remotos orbital para o monitoramento da atividade agrícola, o principal desafio está em desenvolver uma metodologia sistemática sincronizada com as necessidades do mercado.…”

Evolution of Cerrado Vegetal Cover on a River Island Based on Orbital Imaging Data

“…Among the geo-technologies used for identification and evaluation of changes in structure, physiognomy and dynamics of vegetal coverage across different dates, it is noteworthy mention spectral change detection by vegetation indices (JUNGES et al, 2013;SEXTON et al, 2013;DALPOSSO et al, 2013;HILL et al, 2012). Normalized Difference Vegetation Index (NDVI) is one of the vegetation indices most used in studies of plant coverage, since it allows evaluating vegetation conditions and respective spatiotemporal changes (SOUTHWORT et al, 2013;GIRI et al, 2013;TOWNSHEND et al, 2012).…”

Temporal dynamics of spectral reflectance and vegetation indices during canola crop cycle in southern Brazil

“…Annual crops usually display only one peak for vegetation indices (KLERING et al, 2013;JUNGES et al, 2013). This is useful information, as it may be used to distinguish canola crops in satellite imagery-based crop monitoring and mapping studies.…”