The on-water radiometric approach employs a unique provision to obtain water-leaving radiance from nadir (L_w(λ)) which can be used for the calibration of ocean color satellites. In this effort, we address the measurement precision associated with L_w(λ) from a single on-water instrument, which is an important aspect of measurement uncertainty. First, we estimated the precision as the ratio of the standard deviation of the means of repeated measurements to the mean of these measurements. We show that the measurement precision for L_w(λ) is within 2.7–3.7% over 360–700 nm. The corresponding remote sensing reflectance spectra (R_rs(λ)) from the same instrument also exhibit a high precision of 1.9–2.8% in the same spectral domain. These measured precisions of radiance and reflectance over the 360–700 nm range are independent of the optical water type. Second, we quantified the consistency of on-water L_w(λ) and R_rs(λ) from two collocated systems for further insight into their measurement repeatability. The comparison reveals that L_w(λ) measurements in the 360–700 nm agree with each other with an absolute percentage difference of less than 3.5%. The corresponding R_rs(λ) data pairs are subjected to increased differences of up to 8.5%, partly due to variable irradiance measurements (E_s(λ)). The evaluation of measurement precision corroborates the reliability of the on-water acquisition of radiometric data for supporting satellite calibration and validation.

中文翻译：

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不同水域光谱离水辐射率测量精度的实验分析

水上辐射测量方法采用了一项独特的规定，可从最低点（L _w（λ））获得离水辐射率，该辐射率可用于校准海洋彩色卫星。在这项工作中，我们通过单个水上仪器解决与L _w（λ）相关的测量精度，这是测量不确定度的重要方面。首先，我们将重复测量的平均值的标准偏差与这些测量的平均值之比估算为精度。我们表明，在360-700 nm范围内，L _w（λ）的测量精度在2.7-3.7％范围内。相应的遥感反射光谱（R同一仪器的_rs（ λ））在相同的光谱域内也显示出1.9–2.8％的高精度。这些在360–700 nm范围内测得的辐射和反射率精度与光学水类型无关。其次，我们从两个并置系统中量化了水上L _w（ λ）和R _rs（ λ）的一致性，以进一步了解其测量可重复性。比较表明，在360–700 nm范围内的L _w（ λ）测量彼此吻合，绝对百分比差小于3.5％。对应的R _rs（ λ）数据对的差异最大可增加8.5％，部分原因是辐照度测量值可变（E _s（λ））。对测量精度的评估证实了在水上采集辐射数据以支持卫星校准和验证的可靠性。