University of Twente Student Theses


Use of an Airborne Imaging Spectrometer as a Transfer Standard for Atmospheric Correction of SPOT- HRG Data

Bhowmick, Debajyoti (2009) Use of an Airborne Imaging Spectrometer as a Transfer Standard for Atmospheric Correction of SPOT- HRG Data.

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Abstract:Earth Observation (EO) data products are required for environmental monitoring and for use in various ecosystem and climatological models that are essential for the advance of Earth system science in securing our planet’s future. They are often used in combination with in-situ measurements for long term monitoring and modelling. To have confidence in such remotely sensed data in accurately estimating geo-biophysical parameters, they need to be validated and quality assured. This requires establishing relationship between field measurements and imagery through upscaling and data aggregation. This up-scaling is non-trivial when the effect of the atmosphere and the very different scales are considered. For example, surface reflectance are scattered and absorbed by the atmosphere before reaching the sensor placed within or at the top-of-atmosphere (TOA). In order to address such issues, this research uses an imaging spectrometer as a transfer standard to account for the effect of atmosphere between field measurements taken on the ground to that measured by a high resolution satellite sensor placed at TOA. Specim AISA-Eagle imaging spectrometer was used as the transfer standard and SPOT-HRG as the high resolution satellite data. All data were obtained as part of the NCAVEO 2006 field campaign. The objective was to use the imaging spectrometer as a transfer standard for atmospheric correction of SPOT-HRG data in order to provide a validated, quality assured data product. Imaging spectrometers in hyperspectral mode have the capability of resolving the intensity of minor atmospheric absorption features and scattering curve, allowing correction of spectra to values of reflectance (Clark et al. 2002). Calibration quality and radiometric linearity of the Eagle sensor was checked with the NERC-CASI-2 sensor, taken to be the standard in this research. A hybrid atmospheric correction method known as the RTGC (USGS) was applied on the Eagle data to obtain a fine resolution reflectance map. It was then validated using two approaches, (i) direct validation with measured ground targets and (ii) indirect validation with an independent reflectance map produced from the EA-CASI-3 sensor. Direct validation agreed to about within ±2 units of absolute reflectance and indirect validation agreed to about ±1.5 units. The Eagle reflectance map was then used to atmospherically correct the SPOT-HRG data using the ELM model to produce the SPOT reflectance map. It was then validated with the Eagle reflectance map and compared with another independent SPOT reflectance map. The results from this research established the potential use of the Eagle imaging spectrometer as a transfer standard in atmospheric correction of SPOT-HRG in providing accurate, validated and quality assured data, which is traceable with known uncertainty.
Item Type:Essay (Master)
Faculty:ITC: Faculty of Geo-information Science and Earth Observation
Programme:Geoinformation Science and Earth Observation MSc (75014)
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