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Seasonal separation of African savanna components using WorldView-2 imagery : a comparison of pixel- and object-based approaches and selected classification algorithms

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Authors

Kaszta, Zaneta
Van De Kerchove, Ruben
Ramoelo, Abel
Cho, Moses Azong
Madonsela, Sabelo
Mathieu, Renaud
Wolff, Eleonore

Journal Title

Journal ISSN

Volume Title

Publisher

MDPI Publishing

Abstract

Separation of savanna land cover components is challenging due to the high heterogeneity of this landscape and spectral similarity of compositionally different vegetation types. In this study, we tested the usability of very high spatial and spectral resolution WorldView-2 (WV-2) imagery to classify land cover components of African savanna in wet and dry season. We compared the performance of Object-Based Image Analysis (OBIA) and pixel-based approach with several algorithms: k-nearest neighbor (k-NN), maximum likelihood (ML), random forests (RF), classification and regression trees (CART) and support vector machines (SVM). Results showed that classifications of WV-2 imagery produce high accuracy results (>77%) regardless of the applied classification approach. However, OBIA had a significantly higher accuracy for almost every classifier with the highest overall accuracy score of 93%. Amongst tested classifiers, SVM and RF provided highest accuracies. Overall classifications of the wet season image provided better results with 93% for RF. However, considering woody leaf-off conditions, the dry season classification also performed well with overall accuracy of 83% (SVM) and high producer accuracy for the tree cover (91%). Our findings demonstrate the potential of imagery like WorldView-2 with OBIA and advanced supervised machine-learning algorithms in seasonal fine-scale land cover classification of African savanna.

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Keywords

Land cover, Classifiers, Random forest (RF), Support vector machines (SVM), Classification and regression trees (CART), Maximum likelihood (ML), k-Nearest neighbor (k-NN), WorldView-2 (WV-2)

Sustainable Development Goals

Citation

Kaszta, Z, Van De Kerchove, R, Ramoelo, A, Cho, MA, Madonsela, S, Mathieu, R & Wolff, E 2016, 'Seasonal separation of African savanna components using WorldView-2 imagery : a comparison of pixel- and object-based approaches and selected classification algorithms', Remote Sensing, vol. 8, art. no. 763, pp. 1-19.