Verification of Atmospheric Correction for AVH|RR data by Radiometric Simulation Software 6S
Takayuki*, Shoji Takeuchi**, Koji Kajiwara* and Ryutaro Tateishi*
*Center for Environmental Remote Sensing (CEReS), Chiba University, Japan
1-33 Yayoi-cho Inage-ku, Chiba 263 Japan
**Remote Sensing Technology Center of Japan (Restec)
1-9-9, Roppongi, Minato-Ku, Tokyo 106 Japan
Abstract
Remotely sensed data is affected by absorption and scattering of the atmosphere. Second Simulation of the Satellite Signal in the Solar Spectrum(6S) is software to simulate these effect with many parameters such as geometric condition, concentration of atmosphere, component of aerosols, etc. Through the 6S is used for atmosphere correction, recently. However , there is no verify the effectiveness of 6S for atmosphere correction using AVHRR data with different geometric conditions.
Introduction
Remote sensor, such as MSS,TM and AVHRR measure radiance reflected from the earth surface at different wavelengths. Reflectance data is used for many applications, for example classification, change detections and so on. However radiance is affected by various factors. If accurate data is required, these effects must be removed from radiance.
These calibration and correction are as follows.
- Preflight calibiration
- Calibiration considering the sensor degradation
- Solar zenith angle correction
- atmospheric correction
this study deals with atmospheric correction.
If there is no atmosphere on the earth, radiance which reflected the surface is not affected. But in the actual case, the signal is perturbed by the presence of atmosphere on the path sun-target-sensor. Only a fraction of the photons coming from the target reaches the satellite sensor, typically 80% at 850nm and 50% at 450nm, so that the target seems less reflecting(6S User Guide, 1994). These effectives constitute to processes, absorption and scattering. Absorption caused by only O3.H2O,O2,CO2,CH4
and N2O. Scattering caused by dust like, oceanic, water soluble and soot component.
These compositions and concentrations changes on account of the time and the location. And these data are not available. Therefore, it is impossible to perform atmospheric corrections using atmospheric data. Therefore, atmospheric data must be assumed.
6s is radiometric simulation software which used for atmospheric corrections recently. However the effectiveness of the atmospheric corrections has not been verified. In this study, atmospheric correction was performed by 6S for multi-temporal AVHRR data and verified effectiveness of 6S for atmospheric corrections
2.Radiometric simulation software 6S
6S is radiometric simulation software presented in 1994. This program is initially developed as 5s in 1984 and is used for radiometric simulation with combination of various parameters as follows
- apparent reflectance
- effectiveness from absorption
- effectiveness from scattering etc.
Input parameters are as follows
- Geometric condition (Type of sensor, day , month, latitude, longitude)
- Concentration of H2O and O3 in atmosphere
- component of aerosols
- wavelength of observation
- Height of Target
- Land cover type and reflectance of target etc.
User can either input these parameters or select given values for each parameter.
