Spectral unmixing of normalized reflectance data for the deconvolution of lichen and rock mixtures
- Author:
- Zhang J., Rivard B. & Sánchez-Azofeifa A.
- Year:
- 2005
- Journal:
- Remote Sensing of Environment
- Pages:
- 95: 57-66
- Url:
In subarctic regions the ubiquitous presence of rock encrusting lichens compromises the ability to map the reflectance signatures of
minerals from imaging spectrometer data. The use of lichen as an endmember in spectral mixture analysis (SMA) may overcome these
limitations. Because lichens rarely completely occupy the Instantaneous Field of View (IFOV), it is difficult to define a lichen endmember
from an image using visual or automated endmember extraction tools. Spectral similarity of various crustose/foliose lichen species in the
short wave infrared (SWIR) suggests that spectral unmixing of rock and lichens may be successfully accomplished using a single lichen
endmember for this spectral range. We report the use of a spectral normalization method to minimize differences in SWIR reflectance
between five lichen species (U. torrefacta, R. bolanderi, R. geminatum, R. geographicum, A. cinerea). When the normalization is applied to
reflectance spectra from 2000–2400 nm acquired for a lichen encrusted quartzite rock sample we show that only a single lichen endmember is
required to account for the lichen contribution in the observed mixtures. In contrast, two such endmembers are required when the
normalization is not applied to the reflectance data. We illustrate this point using examples where endmembers are extracted manually and
automatically, and compare the SMA results against abundances estimated from digital photography. For both the reflectance and normalized
reflectance data, SMA results correlate well (R2N0.9) with abundances estimated from digital photography. The use of normalized reflectance
implies that any field/laboratory lichen spectrum can be selected as the lichen endmember for SMA of airborne/spaceborne imagery.
Keywords: Spectral mixture analysis; Normalization; Lichen; Mineral
- Id:
- 13420
- Submitter:
- zdenek
- Post_time:
- Monday, 22 June 2009 11:18