Derivation of High Spatial Resolution Albedo from UAV Digital Imagery: Application over the Greenland Ice Sheet
Derivation of High Spatial Resolution Albedo from UAV Digital Imagery: Application over the Greenland Ice Sheet
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DOI：
10.3389/feart.2017.00040
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发表时间：
2017-05
影响因子：
2.9
通讯作者：
J. Ryan;A. Hubbard;J. Box;S. Brough;Karen A. Cameron;J. Cook;M. Cooper;S. Doyle;A. Edwards;T. Holt;T. Irvine‐Fynn;Christine Jones;L. Pitcher;Å. Rennermalm;L. Smith;M. Stibal;N. Snooke
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文献类型：
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作者：
J. Ryan;A. Hubbard;J. Box;S. Brough;Karen A. Cameron;J. Cook;M. Cooper;S. Doyle;A. Edwards;T. Holt;T. Irvine‐Fynn;Christine Jones;L. Pitcher;Å. Rennermalm;L. Smith;M. Stibal;N. Snooke
测量反照率是模拟整个地球冰冻圈表面融化的先决条件，但现有的卫星产品在空间和/或时间分辨率上是有限的。在这里，我们提出了一种实用的方法，使用消费级数码相机和无人机(UAV)技术来获得精度为5%的厘米级反照率产品。我们的方法包括使用白色参考靶处理、校正和校准原始数字图像的工作流程，以及来自宽带硅视强计的向上和向下短波辐射测量。我们用一组无人机在格陵兰冰盖的西部K区上空演示了这一方法。由此产生的反照率产品UAV10A1覆盖280平方公里，分辨率为每像素20厘米，与MOD10A1相比，均方根差为3.7%，与地面宽带辐射计测量结果相比，均方根差为4.9%。通过连续测量向下的太阳辐照度，该技术克服了以前在冰川地形上进行调查期间和调查之间由于光照条件变化而造成的限制。目前多光谱传感器的小型化和无人机组件上的向上辐射传感器意味着，这项技术很可能在实地研究中变得越来越有吸引力，并将在高时间和空间分辨率的碎片、尘埃、冷锥石和生物反照率表面测绘以及直接约束表面能量平衡模型的广泛应用中使用。
Measurements of albedo are a prerequisite for modelling surface melt across the Earth's cryosphere, yet available satellite products are limited in spatial and/or temporal resolution. Here, we present a practical methodology to obtain centimetre resolution albedo products with accuracies of 5% using consumer-grade digital camera and unmanned aerial vehicle (UAV) technologies. Our method comprises a workflow for processing, correcting and calibrating raw digital images using a white reference target, and upward and downward shortwave radiation measurements from broadband silicon pyranometers. We demonstrate the method with a set of UAV sorties over the western, K-sector of the Greenland Ice Sheet. The resulting albedo product, UAV10A1, covers 280 km2, at a resolution of 20 cm per pixel and has a root-mean-square difference of 3.7% compared to MOD10A1 and 4.9% compared to ground-based broadband pyranometer measurements. By continuously measuring downward solar irradiance, the technique overcomes previous limitations due to variable illumination conditions during and between surveys over glaciated terrain. The current miniaturization of multispectral sensors and incorporation of upward facing radiation sensors on UAV packages means that this technique will likely become increasingly attractive in field studies and used in a wide range of applications for high temporal and spatial resolution surface mapping of debris, dust, cryoconite and bioalbedo and for directly constraining surface energy balance models.