## 4 Experimental Results
### Qualitative Comparison  
The cloud shadow compensation comparison results effectively show the difference in a single shadow area. Figures 4-6 show that our method obtained better results in brightness, contrast, and original colors than the other methods. OWC's results indicate that the brightness was rising while the contrast was almost unchanging. LCC, GMC, HMT, CRM, and OOPR improved both the brightness and contrast to some extent and the original color of the objects in the shadow areas was recovered (e.g., the trees in Figure 4 are depicted in their true green color). HMT produced the best and most stable capability for improving the contrast while the other methods' contrast indicated another problem of uneven compensation in a single shadow area. The part of the cloud shadow area that was obscured by the thicker cloud is still slightly darker than the thinner part after compensation in almost all the reference methods. In comparison, this uneven compensation problem was solved by the multilevel combination strategy. For the bare land in Figure 5, there is a small non-shadow region that is recognized as shadows. This part was easily overcompensated by other methods, but our method addressed this phenomenon because its local window information was useful in adaptively enhancing each partially shaded information to the same level as the non-shadow area. Thus, our model recovered the information as accurately as possible and showed almost no difference in comparison to the non-shadow areas. Figure 4: Cloud shadow compensation results in satellite Image 1. (**a**) Original image; (**b**) Shadow detection result (red); (**c**) The OWC result; (**d**) The GMC result; (**e**) The HMT result; (**f**) The LCC result; (**g**) The CRM result; (**h**) The OOPR result; (**i**) Our method’s result. Figure 5: _Cont._  
Regarding ground object shadow compensation, our method produced better results, which indicated its ability to compensate for each shadow region. Different shadow regions were improved and were identical to their adjacent non-shadow areas, which was beneficial for avoiding over-compensation or insufficient compensation. Even though the object information shaded by the buildings was too dark to see, our method recovered the information. To depict the compensation results of our method in detail, six portions of Images 4-6 in Figures 7-9 were selected, which are named A-F in Figure 10. From the figures and Table 1, it can be seen that our method produced better visual and quantitative compensation results than the other methods. Figure 5: Cloud shadow compensation results in satellite Image 2. (**a**) Original image; (**b**) Shadow detection result (red); (**c**) The OWC result; (**d**) The GMC result; (**e**) The HMT result;(**f**) The LCC result; (**g**) The CRM result; (**h**) The OOPR result; (**i**) Our method’s result. Figure 6: Cloud shadow compensation results in satellite Image 3. (**a**) Original image; (**b**) Shadow detection result (red); (**c**) The OWC result; (**d**) The GMC result; (**e**) The HMT result; (**f**) The LCC result; (**g**) The CRM result; (**h**) The OOPR result; (**i**) Our method’s result. Figure 8: _Cont._  
Figure 7: Shadow compensation results in aerial Image 4. (**a**) Original image; (**b**) Shadow detection result (red); (**c**) The OWC result; (**d**) The GMC result; (**e**) The HMT result;(**f**) The LCC result; (**g**) The CRM result; (**h**) The OOPR result; (**i**) Our method’s result. Figure 8: Shadow compensation results in aerial Image 5. (**a**) Original image; (**b**) Shadow detection result (red); (**c**) The OWC result; (**d**) The GMC result; (**e**) The HMT result;(**f**) The LCC result; (**g**) The CRM result; (**h**) The OOPR result; (**i**) Our method’s result. Figure 9: _Cont._  
When compared to the non-adaptive methods (OWC, GMC, HMT, and LCC), our approach was able to compensate for shadows more adaptively. Although OWC significantly enhanced the brightness, the shadow areas were still unclear for less heightened contrast.