Clouds and cloud-shadow are a persistent problem in all optical
    satellite imagery. Plenty of methods have been suggested in the literature
    to address this problem, and reconstruct the missing part of the optical signal.
    In this work, three methods representative
    of different approaches to the cloud removal problem are
    compared. The first method
    is temporal fitting using Fourier series, which benefits from the temporal continuity of the
    signal. The second method uses sparse spectral unmixing to fill in the missing areas. The third method employs
    radiometric consistency as a tool to determine the missing part of the
    optical signal. These three methods are first presented and their theoretical background described,
    followed by a discussion of their implied assumptions,
    general performance, and failure modes. A set of experiments using Landsat 8 time series with
    diverse land cover types were conducted. The quantitative results of the
    three methods using simulated clouds as well as real ones are presented.
    Finally, some concluding remarks about the relative advantages of the three
    approaches are listed, in addition to some recommendations about their use.