Proceedings Article | 2 October 2008
KEYWORDS: Soil science, Temperature metrology, Radiometry, Sensors, Error analysis, Algorithm development, Vegetation, Quartz, Black bodies, Thermography
Surface emissivity in the thermal infrared (TIR) region is an important parameter for determining the land surface
temperature from remote sensing measurements. This work compares the emissivities measured by different field
methods (the Box method and the Temperature and Emissivity Separation, TES, algorithm) as well as emissivity data
from ASTER scenes and the spectra obtained from the ASTER Spectral Library. The study was performed with a field
radiometer having TIR bands with central wavelengths at 11.3 μm, 10.6 μm, 9.1 μm, 8.7 μm and 8.4 μm, similar to the
ASTER TIR bands. The measurements were made at two sites in southern New Mexico. The first was in the White
Sands National Monument, and the second was an open shrub land in the Jornada Experimental Range, in the northern
Chihuahuan Desert, New Mexico, USA. The measurements show that, in general, emissivities derived with the Box
method agree within 3% with those derived with the TES method for the spectral bands centered at 10.6 μm and 11.3
μm. However, the emissivities for the shorter wavelength bands are higher when derived with the Box method than those
with the TES algorithm (differences range from 2% to 7%). The field emissivities agree within 2% with the laboratory
spectrum for the 8-13 μm, 11.3 μm and 10.6 μm bands. However, the field and laboratory measurements in general
differ from 3% to 16% for the shorter wavelength bands, i.e., 9.1 μm, 8.6 μm and 8.4 μm. A good agreement between the
experimental measurements and the ASTER TIR emissivity data is observed for White Sands, especially over the 9 - 12
μm range (agreement within 4%). The study showed an emissivity increase up to 17% in the 8 to 9 μm range and an
increase of 8% in emissivity ratio of average channels (8.4 μm, 8.6 μm, 9.1 μm):(10.6 μm, 11.3 μm) for two gypsum
samples with different water content.
