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Remote Sens. 2015, 7(2), 2046-2066; doi:10.3390/rs70202046

Classification of Herbaceous Vegetation Using Airborne Hyperspectral Imagery

1
Research Institute of Remote Sensing and Rural Development, Karoly Robert College, H-3200 Gyöngyös, Mátrai út 36, Hungary
2
MTA-DE Biodiversity and Ecosystem Services Research Group, P.O. Box 71, H-4010 Debrecen, Hungary
*
Author to whom correspondence should be addressed.
Academic Editors: Norbert Pfeifer, Ioannis Gitas and Prasad S. Thenkabail
Received: 13 October 2014 / Revised: 9 January 2015 / Accepted: 21 January 2015 / Published: 12 February 2015
(This article belongs to the Special Issue Remote Sensing and GIS for Habitat Quality Monitoring)
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Abstract

Alkali landscapes hold an extremely fine-scale mosaic of several vegetation types, thus it seems challenging to separate these classes by remote sensing. Our aim was to test the applicability of different image classification methods of hyperspectral data in this complex situation. To reach the highest classification accuracy, we tested traditional image classifiers (maximum likelihood classifier—MLC), machine learning algorithms (support vector machine—SVM, random forest—RF) and feature extraction (minimum noise fraction (MNF)-transformation) on training datasets of different sizes. Digital images were acquired from an AISA EAGLE II hyperspectral sensor of 128 contiguous bands (400–1000 nm), a spectral sampling of 5 nm bandwidth and a ground pixel size of 1 m. For the classification, we established twenty vegetation classes based on the dominant species, canopy height, and total vegetation cover. Image classification was applied to the original and MNF (minimum noise fraction) transformed dataset with various training sample sizes between 10 and 30 pixels. In order to select the optimal number of the transformed features, we applied SVM, RF and MLC classification to 2–15 MNF transformed bands. In the case of the original bands, SVM and RF classifiers provided high accuracy irrespective of the number of the training pixels. We found that SVM and RF produced the best accuracy when using the first nine MNF transformed bands; involving further features did not increase classification accuracy. SVM and RF provided high accuracies with the transformed bands, especially in the case of the aggregated groups. Even MLC provided high accuracy with 30 training pixels (80.78%), but the use of a smaller training dataset (10 training pixels) significantly reduced the accuracy of classification (52.56%). Our results suggest that in alkali landscapes, the application of SVM is a feasible solution, as it provided the highest accuracies compared to RF and MLC. SVM was not sensitive in the training sample size, which makes it an adequate tool when only a limited number of training pixels are available for some classes. View Full-Text
Keywords: grassland; habitat mapping; hyperspectral; maximum likelihood classifier; minimum noise fraction; nature conservation; open landscape; random forest; support vector machine grassland; habitat mapping; hyperspectral; maximum likelihood classifier; minimum noise fraction; nature conservation; open landscape; random forest; support vector machine
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Burai, P.; Deák, B.; Valkó, O.; Tomor, T. Classification of Herbaceous Vegetation Using Airborne Hyperspectral Imagery. Remote Sens. 2015, 7, 2046-2066.

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