*5.5. Ablation Study on OHEM*

Table 11 shows the quantitative detection results of ShadowDeNet with and without OHEM. From Table 11, SDAL can improve the overall performance of ShadowDeNet by ~1.3% *f* 1 accuracy and ~1.5% *ap* accuracy, which shows its effectiveness. Although the detection rate is not very sensitive to OHEM, the false alarm rate is decreased greatly by ~4.0% when OHEM is used. This is because OHEM can mine hard negative samples and train them repeatedly and emphatically. Finally, the foreground–background discrimination ability of ShadowDeNet can be boosted further.

**Table 11.** Quantitative results of ShadowDeNet with and without OHEM.

