1. 北京大学地球与空间科学学院空间信息集成与3S工程应用北京市重点实验室，北京 100871 2. Center for Remote Sensing and Mapping Science, the University of Georgia, Athens, Georgia 30602, USA 3. 河北省气象科学研究所河北省生态环境监测实验室，河北 石家庄 050021 4. 东北师范大学城市与环境科学学院，吉林 长春 130024
The Multi-angle Polarization Spectral Character of Water and Its Applications in Water Color Remote Sensing
1. Beijing Key Lab of Spatial Information Integration and 3S Engineering Applications, School of Earth and Space Science, Peking University, Beijing 100871, China 2. Center for Remote Sensing and Mapping Science, the University of Georgia, Athens, Georgia 30602, USA 3. Hebei Meteorological Institute & Hebei Eco-Environmental Monitoring Laboratory, Shijiazhuang 050021, China 4. College of Urban and Environmental Sciences, Northeast Normal University, Changchun 130024, China
Abstract：The reflectance of pure water is very low at visible and near infrared bands. Its spectral characteristics are not obvious. Water always shows dark hue in optical remote sensing images. This dark hue causes the difficulties in water remote sensing identification. There is an interesting phenomenon when the authors research the water polarization spectroscopy. The authors measured water’s polarization spectra and reflectance spectra at different view zenith angles using the ASD spectrometer. When the view zenith angle was zero (measured vertically), as the spectrum people commonly measure, there was no polarization phenomenon at the water surface, and the reflectance was low at each band. Along with the increase in view zenith angle, the DOP spectra curves increased evidently, while the reflectance curves only changed a little. When the view zenith angle was over 30 degree, the values of DOP spectrum were much larger than the reflectance spectrum values at the entire visible and near infrared bands. At some bands, the DOP value was several dozen times than its reflectance value. This phenomenon shows that the water’s brightness in DOP image is much higher than its brightness in intensity image under the same condition. This rule was verified by the PARASOL multiangle polarization satellite data. Comparing the average brightness of DOP images with the average brightness of intensity images at 490, 670 and 865 nm band, the former is higher than the latter apparently. The brighter DOP images are better for water remote sensing identification. It is the first time that the authors found this special multiangle polarization spectral character of water. It revealed the advantage of water detection using the multiangle polarization remote sensing data. This method solved the low reflectivity problem of water color remote sensing. It will greatly improve the capability of water remote sensing identification and the retrieval accuracy of water quality parameters.
Key words：Spectrum;Polarization;Multi-angle;Remote sensing;Water color
吴太夏1,2，晏 磊1*，相 云1,3，赵云升4，陈 伟1 . 水体的多角度偏振波谱特性及其在水色遥感中应用[J]. 光谱学与光谱分析, 2010, 30(02): 448-452.
WU Tai-xia1,2,YAN Lei1*, XIANG Yun1,3, ZHAO Yun-sheng4,CHEN Wei1 . The Multi-angle Polarization Spectral Character of Water and Its Applications in Water Color Remote Sensing . SPECTROSCOPY AND SPECTRAL ANALYSIS, 2010, 30(02): 448-452.
[1] Shaw J A, Marston C. Optics Express，2000, 7(11): 375. [2] Cox C, Munk W. Journal of the Optical Society of America, 1954, 44(11): 838. [3] LI Yan, LI Jing(李 炎，李 京). Chinese Science Bulletin(科学通报), 2000, 45(10): 925. [4] Wu Taixia, Zhao Yunsheng. IEEE Transactions on Geoscience and Remote Sensing, 2005, 43(12): 2854. [5] Henderson Bradley G, Theiler James, et al. Remote Sensing of Environment, 2003, 88(4): 453. [6] Li X W，Strahler A H. IEEE Trans. Geosci. Remote Sensing, 1992, 30(2): 276. [7] Csiszar I，Gutman G，Romanov P，et al. Remote Sensing of Environment，2001, 76(3): 399. [8] Leroy M, Bréon F M. Remote Sensing of Environment, 1996, 57(2): 97. [9] Egan W G，Duggin M J. Proc. SPIE，2000, 4133: 172. [10] Shaw J A. Applied Optics, 1999, 38(15): 3157. [11] Azzam R M A, Bashara N M. Ellipsometry and Polarized Light. North-Holland Publishing Company, 1997. 1. [12] Nadal F，Bréon F M. IEEE Transactions on Geoscience and Remote Sensing, 1999, 37(3): 1709. [13] Bacour C，Bréon F M. Remote Sensing of Environment, 2005, 98(1): 80. [14] Jozsef Gal, Gabor Horvath，et al. Remote Sensing of Environment, 2001, 76(1): 103. [15] Heege T, Fischer J. Proc. SPIE Ocean Optics, 2000, 10: 16.
