基于交叉点不符值的ICESat冰盖测高精度估计
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摘要
凭借地面光斑小、分辨率高等特点,ICESat卫星激光测高数据在两极冰盖的研究中得到了广泛的应用。为了确定ICESat在冰面上的测高能力,本文利用格陵兰地区的ICESat交叉点不符值对其在冰盖表面的观测值精度进行了估计;并在充分考虑冰盖时变影响的条件下对交叉点不符值进行了统计。结果表明,其观测精度与地表反射面的坡度存在明显的线性关系,特别是在坡度小于1°的条件下,其相关性高达0.985。进一步考虑地表起伏对于高程内插的影响以后,得到理想环境下ICESat在冰面上的单点测高精度约为±6.4 cm。
ICESat satellite laser altimetry data have a wide range of applications in the researches of polar ice sheets since its characteristics of small footprint and high resolution. To determine the ability of ICESat altimetry over ice surface, its accuracy over ice sheet is estimated based on crossover differences in Greenland. Considering the influence of elevation change of ice sheet, the crossover differences are statistically analyzed and an evident linear relationship between its accuracy and the slope of the reflecting surface is shown according to the results. Particularly,the correction is up to 0.985 when the slope is less than 1°. With further consideration of the influence of surface undulation upon elevation interpolation, an accuracy of about ±6.4 cm is obtained for single point elevation measurement of ICESat observation over ice surface.
ICESat satellite laser altimetry data have a wide range of applications in the researches of polar ice sheets since its characteristics of small footprint and high resolution. To determine the ability of ICESat altimetry over ice surface, its accuracy over ice sheet is estimated based on crossover differences in Greenland. Considering the influence of elevation change of ice sheet, the crossover differences are statistically analyzed and an evident linear relationship between its accuracy and the slope of the reflecting surface is shown according to the results. Particularly,the correction is up to 0.985 when the slope is less than 1°. With further consideration of the influence of surface undulation upon elevation interpolation, an accuracy of about ±6.4 cm is obtained for single point elevation measurement of ICESat observation over ice surface.
引文
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[15] DIMARZIO J P,BRENNER A,SCHUTZ B,et al. GLAS/ICESat 1 km laser altimetry digital elevation model of Greenland[EB/OL].(2007-06-15)[2018-03-10]. http:∥nsidc. org/data/docs/daac/nsidc0304_0305_glas_dems.gd.html.
[16]王丽红,张传定,王俊勤,等.航空重力测量数学模型及其测量精度分析[J].测绘科学技术学报,2008,25(1):68-71.WANG L H,ZHANG C D,WANG J Q,et al. Mathematical models and accuracy evaluation for the airborne gravimetry[J].Journal of Geomatics Science and Technology,2008,25(1):68-71.
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[2] HOWAT I M,SMITH B E,JOUGHIN I,et al. Rates of southeast Greenland ice volume loss from combined ICESat and ASTER observations[J]. Geophysical Research Letters,2008,35(17):179-190.
[3] SLOBBE D,LINDENBERGH R,DITMAR P. Estimation of volume change rates of Greenland’s ice sheet from ICESat data using overlapping footprints[J]. Remote Sensing Of Environment,2008,112(12):4204-4213.
[4] PRITCHARD H D,ARTHEM R J,VAUGHAN D G,et al.Extensive dynamic thinning on the margins of the Greenland and Antarctic ice sheets[J]. Nature,2009,461(7266):971-975.
[5] GUNTER B,URBAN T,RIVA R,et al. A comparison of coincident GRACE and ICESat data over Antarctica[J]. Journal of Geodesy,2009,83(11):1051-1060.
[6] SORENSEN L S,SIMONSEN S B,NIELSEN K,et al. Mass balance of the Greenland ice sheet(2003! 2008)from ICESat data:The impact of interpolation,sampling and firn density[J]. The Cryosphere,2011,5(1):173-186.
[7] GARDNER A S,MOHOLDT G,COGLEY J G,et al. A Reconciled Estimate of Glacier Contributions to Sea Level Rise:2003 to 2009[J]. Science,2013,340(6134):852-857.
[8] FRICKER H A. Assessment of ICESat performance at the salar de Uyuni,Bolivia[J]. Geophysical Research Letters,2005,32(21):1-5.
[9] SHUMAN C A,ZWALLY H J,SCHUTZ B E,et al. ICESat Antarctic elevation data:Preliminary precision and accuracy assessment[J]. Geophysical Research Letters,2015,33(33):359-377.
[10] BRENNER A C,DIMARZIO J P,ZWALLY H J. Precision and accuracy of satellite radar and laser altimeter data over the continental ice sheets[J]. IEEE Transactions on Geoscience and Remote Sensing,2007,45(2):321-331.
[11] BAMBER J L,GRIGGS J A,HURKMANS R T W L,et al. A new bed elevation dataset for Greenland[J]. The Cryosphere,2013,7(2):499-510.
[12] ZWALLY H J,YI D,KWOK R,et al. ICESat measurements of sea ice freeboard and estimates of sea ice thickness in the Weddell Sea[J]. Journal of Geophysical Research,2008,113:C02S15.
[13]陈国栋.利用ICESat数据确定北极冰雪消融方法的研究[D].武汉:武汉大学,2015:38-44.CHEN G D. Study on the methodology of determing ice and snow melting in Arctic using ICESat data[D]. Wuhan:Wuhan University,2015:38-44.
[14] ZWALLY H J,JUN L,BRENNER A C,et al. Greenland ice sheet mass balance:distribution of increased mass loss with climate warming; 2003-07 versus 1992-2002[J]. Journal of Glaciology,2011,57(201):88-102.
[15] DIMARZIO J P,BRENNER A,SCHUTZ B,et al. GLAS/ICESat 1 km laser altimetry digital elevation model of Greenland[EB/OL].(2007-06-15)[2018-03-10]. http:∥nsidc. org/data/docs/daac/nsidc0304_0305_glas_dems.gd.html.
[16]王丽红,张传定,王俊勤,等.航空重力测量数学模型及其测量精度分析[J].测绘科学技术学报,2008,25(1):68-71.WANG L H,ZHANG C D,WANG J Q,et al. Mathematical models and accuracy evaluation for the airborne gravimetry[J].Journal of Geomatics Science and Technology,2008,25(1):68-71.
[17] BRENNER A C,ZWALLY H J,BENTLEY C R,et al. Geoscience Laser Altimeter System(GLAS)algorithm theoretical basis document[EB/OL].(2012-02-15)[2018-03-10]. http:www.csr.utexas.edu/glas/atbd.html.