In situ remote sensing reflectance (R_rs) measured using the above-water approach usually suffers from residual reflected skylight (Δ), and thus its applicability is limited. In this study, we proposed a simple method, which only required the in situ R_rs spectrum itself as input, to further remove the Δ effects in the in situ R_rs spectrum. The performance of the proposed method was evaluated using both simulation data and in situ R_rs spectra measured using a radiance sensor with a black tube (Δ-free in situ R_rs). The results showed that the proposed method outperformed other existing methods and can be applied to various types of waters. For example, from the two simulation experiments, it was seen that the proposed method can provide accurate R_rs spectra with a mean absolute percentage error (MAPE) = 6% even if they are measured under various sky conditions and wind speeds (using Hydrolight) and can estimate accurate Δ values with MAPE = 5% (using a simple bio-optical model). From a comparison analysis using Δ-free in situ R_rs data, the proposed method also showed the best performance with the smallest MAPE of 45% (MAPE ranged from 52% to 260% for other existing methods). In addition, the proposed method can improve the quality of R_rs spectra collected under various sky conditions (clear, scattered clouds and overcast), with an increased proportion of higher quality assurance scores. Two showcases indicate that the Δ corrections should be carried out for all above water approach-measured R_rs spectra before they are applied to develop water quality estimation algorithms or to evaluate the performances of atmospheric correction algorithms.

使用上述水上方法测得的原位遥感反射率（R _rs）通常会受到残留的反射天光（Δ）的影响，因此其适用性受到限制。在这项研究中，我们提出了一种简单的方法，该方法仅需要将原位R _rs光谱本身作为输入，以进一步消除原位R _rs光谱中的Δ效应。同时使用模拟数据以及原位所提出的方法的性能进行了评价- [R _RS使用辐射传感器用黑色管（Δ -自由原位光谱测量ř _RS）。结果表明，该方法优于其他现有方法，可应用于各种类型的水域。例如，从两个模拟实验中可以看出，即使在各种天空条件和风速下（使用Hydrolight）进行测量，所提出的方法也可以提供平均绝对百分比误差（MAPE）= 6％的准确R _rs光谱。并且可以使用MAPE = 5％估算出准确的Δ值（使用简单的生物光学模型）。通过使用无Δs原位R _rs数据进行的比较分析，提出的方法还显示了最佳性能，MAPE最小为45％（对于其他现有方法，MAPE范围为52％至260％）。另外，该方法可以提高R _rs的质量。在各种天空条件下（清晰，零散的云层和阴天）收集的光谱，并且更高的质量保证得分比例越来越大。两个展示表明，在对所有上述水上方法测得的R _rs光谱进行Δ校正之前，应将其应用于开发水质估算算法或评估大气校正算法的性能。