Comparison analysis of spatial and spectral feature in vegetation classification based on AVIRIS hyperspectral image

Abstract

With the development of hyperspectral sensor technology and remote sensing data acquisition platform, the application of hyperspectral data is becoming more and more popular in precision agriculture. Spectral features and spatial features are two main kinds of features used in hyperspectral image classification. The comparison of spectral features and spatial features in vegetation classification of hyperspectral image is a special application in hyperspectral image classification. Therefore, this study compared the performance of several typical spectral features and spatial features in vegetation classification of hyperspectral image. The considered spatial features include grey level co-occurrence matrix (GLCM) based features, Gabor features and morphological features. The considered spectral feature selection or extraction methods include minimal-redundancy-maximal-relevance (mRMR), joint mutual information (JMI), conditional mutual information maximization (CMIM), double input symmetrical relevance (DISR), Jeffreys-Matusita (JM), principal component analysis (PCA), independent component analysis (ICA) and linear discriminant analysis (LDA). PCA, an effective subspace feature extraction method, is widely used in the feature extraction of hyperspectral image. The first several principal components (PCs) are usually selected as spectral features in hyperspectral image classification. However, the first several PCs have no guarantee to achieve good class separability and classification accuracy. Considering that, a hybrid feature extraction approach named as PCA_ScatterMatrix was proposed which combined PCA and an improved scatter-matrix-based feature selection method, aiming to select PCs with high class separability and get high overall classification accuracy. The experiments and comparative analyses were conducted with a widely used hyperspectral image, which was collected over the agricultural area in northwestern Indiana, USA (United States of America) by the AVIRIS (Airborne Visible / Infrared Imaging Spectrometer). The experimental results indicated that: (1) The proposed hybrid feature extraction method PCA_ScatterMatrix got the highest overall classification accuracy on both data sets (82.7% and 86.5%) among three classic subspace feature extraction methods (PCA, ICA and LDA) and respectively improved overall classification accuracy by 1.5% and 2.5% on both data sets, comparing to original PCA; (2) Compared to spectral features, spatial feature extraction methods generally got higher overall classification accuracy, especially Gabor spatial features got the highest overall classification accuracy on both data sets (95.5% and 96.7%). The results suggest that the proposed method is effective in vegetation classification of hyperspectral image and the spatial features play a much more important role in vegetation classification of hyperspectral image, comparing with spectral features.

Keywords

• hyperspectral image
• vegetation classification
• spectral feature
• spatial feature
• hybrid feature extraction method
• scatter-matrix
• principal component analysis