International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B7, 2012
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia
MAPPING THE WETLAND VEGETATION COMMUNITIES OF THE AUSTRALIAN
GREAT ARTESIAN BASIN SPRINGS USING SAM, MTMF AND SPECTRALLY
SEGMENTED PCA HYPERSPECTRAL ANALYSES
D. C. White *, M. M. Lewis
CORRESPONDING AUTHOR: *Davina C. White, Postdoctoral Research Fellow, Landscape Futures Program, The
Environment Institute, The University of Adelaide, South Australia, E-mail: davina.white@adelaide.edu.au, Tel: +61
(0)8 8303 8112, Fax.: +61 (0)8 8303 6717.
TECHNICAL SESSION: Technical Commission VII, WG VII/3
KEY WORDS: Hyperspectral, Environment, Ecosystem, Analysis, Vegetation; Monitoring; Spectral
ABSTRACT:
The Australian Great Artesian Basin (GAB) supports a unique and diverse range of groundwater dependent wetland ecosystems
termed GAB springs. In recent decades the ecological sustainability of the springs has become uncertain as demands on this iconic
groundwater resource increase. The impacts of existing water extractions for mining and pastoral activities are unknown. This
situation is compounded by the likelihood of future increasing demand for extractions.
Hyperspectral remote sensing provides the necessary spectral and spatial detail to discriminate wetland vegetation communities.
Therefore the objectives of this paper are to discriminate the spatial extent and distribution of key spring wetland vegetation
communities associated with the GAB springs evaluating three hyperspectral techniques: Spectral Angle Mapper (SAM), Mixture
Tuned Matched Filtering (MTMF) and Spectrally Segmented PCA. In addition, to determine if the hyperspectral techniques
developed can be applied at a number of sites representative of the range of spring formations and geomorphic settings and at two
temporal intervals.
Two epochs of HyMap airborne hyperspectral imagery were captured for this research in March 2009 and April 2011 at a number of
sites representative of the floristic and geomorphic diversity of GAB spring groups/complexes within South Australia. Colour digital
aerial photography at 30 cm GSD was acquired concurrently with the HyMap imagery. The image acquisition coincided with a field
campaign of spectroradiometry measurements and a botanical survey.
To identify key wavebands which have the greatest capability to discriminate vegetation communities of the GAB springs and
surrounding area three hyperspectral data reduction techniques were employed: (1) Spectrally Segmented PCA (SSPCA); (ii) the
Minimum Noise Transform (MNF); and (iii) the Pixel Purity Index (PPI). SSPCA was applied to NDVI-masked vegetation portions
of the HyMap imagery with wavelength regions spectrally segmented for the VIS-NIR (450-1,350 nm), SWIR 1 (1,400-1,800 nm)
and SWIR 2 (1,950-2,480 nm). The resulting pure endmember image pixels of the vegetation communities identified were used as
target spectra for input into the SAM and MTMF algorithms.
Spring wetland vegetation communities successfully discriminated include low lying reeds and sedges along spring tails (Baumea
spp. and Cyperus spp.), dense homogenous stands of Phragmites australis reeds, and sporadic patches of salt couch grass
(Sparabolus spp.).
Our results indicate that a combination of hyperspectral remote sensing techniques which reduce superfluous wavebands providing a
targeted spectral matching approach are capable of discriminating and mapping key vegetation communities of the GAB springs.
This approach provides reliable baseline mapping of the GAB spring wetland vegetation communities, with repeatability over space
and time. In addition it has the capability to determine the sensitivity of spring wetland vegetation extent, distribution and diversity,
to associated changes in spring flow rates due to water extractions. This approach will ultimately inform water allocation plan
management policies.
1. INTRODUCTION 2003; Gotch et. al., 2008; Ponder, 2004). The GAB springs are
of great national and international importance for their
1.1 Background ecological, scientific and economic values, and are culturally
Th | f : significant to indigenous Australians (Ah Chee, 2002). They
e Australian Great Artesian Basin (GAB) supports a unique have historically provided a vital source of water in the inland
and diverse range of groundwater dependent wetland heart of Australia (Badman et. al., 1996; Boyd, 1990; Mudd,
ecosystems termed GAB springs, which contain a number of ^ 2000), In recent decades the ecological sustainability of the
rare and relic endemic flora and fauna (Fensham and Fairfax,
* Corresponding author.
