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Integrating imaging spectroscopy and neural networks to map grass quality in the Kruger National Park, South Africa
Author
Mutanga, O
Skidmore, A K
Publisher
Remote Sensing of Environment
Publication Year
2004
Body

A new integrated approach, involving continuum-removed absorption features, the red edge position and neural networks, is developed and applied to map grass nitrogen concentration in an African savanna rangeland. Nitrogen, which largely determines the nutritional quality of grasslands, is commonly the most limiting nutrient for grazers. Therefore, the remote sensing of foliar nitrogen concentration in savanna rangelands is important for an improved understanding of the distribution and feeding patterns of wildlife. Continuum removal was applied on two absorption features located in the visible (R550-757) and the SWIR (R2015-2199) from an atmospherically corrected HYMAP MKI image. A feature selection algorithm was used to select wavelength variables from the absorption features. Selected band depths from the absorption features as well as the red edge position (REP) were input into a backpropagation neural network. The best-trained neural network was used to map nitrogen concentration over the whole study area. Results indicate that the new integrated approach could explain 60% of the variation in savanna grass nitrogen concentration on an independent test data set, with a root mean square error (rmse) of 0.13 (±8.30% of the mean observed nitrogen concentration). This result is better compared to the result obtained using multiple linear regression, which yielded an R2 of 38%, with a RMSE of 0.16 (±10.30% of the mean observed nitrogen concentration) on an independent test data set. The study demonstrates the potential of airborne hyperspectral data and neural networks to estimate and ultimately to map nitrogen concentration in the mixed species environments of Southern Africa.

Language
English
Resource Type
Text
Document Type
Journal Issue/Article
Journal Volume
90
Journal Number
1
Journal Pages
104-115
Collection
Southern Africa Collection
Journal Name
Remote Sensing of Environment
Keywords
Hymap imagery
Absorption features
Continuum removal
red edge position
Foliar nitrogen concentration
Savanna rangelands
savanna
rangelands
mapping
plant production
grasslands
forage quality
remote sensing
conservation
national parks
Africa