Cross-Domain Collaborative Enhancement for Tiny Object Detection in Remote Sensing Images
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摘要: 面对遥感影像中广泛分布的小目标,现有遥感影像目标检测方法仍面临严峻挑战,检测精度尚显不足。遥感影像小目标检测核心瓶颈在于小目标正样本匮乏与特征表示弱两大问题。因此,该文提出一种跨域协同增强的遥感影像小目标检测方法(CDCEDet),通过在空间域优化小目标标签分配,在频域提高小目标特征表示,以提升小目标检测性能。具体而言,该文首先设计尺度自适应锚框生成器,依据目标空间分布与几何尺度特性动态生成匹配锚框集合,有效缓解了锚框与小目标之间的尺度失配问题,显著提升了小目标正样本数量。在此基础上,提出分位数自适应标签分配机制,通过建模每个目标与其对应锚框的交并比统计分布动态调整标签分配阈值,有效缓解了固定阈值标签分配下的尺度偏差问题。此外,针对小目标特征表示弱的问题,从频域视角出发,构建频率自适应融合模块,利用自适应高通滤波器以增强小目标细节信息,并结合自适应低通滤波器维持上采样后小目标内部特征的语义一致性,从而提升小目标的特征表示能力。实验结果表明,在AI-TODv2数据集上,所提方法在AP50和AP50-95指标上较现有最优方法提升1.8%和0.7%;在AI-TOD-R数据集上,两项指标分别提升2.6%和0.7%,展现出良好的小目标检测能力和泛化能力。Abstract:
Objective Deep learning has substantially advanced object detection in Remote Sensing Images (RSIs). However, because of imaging conditions and the inherently small size of many objects, a large proportion of targets in RSIs occupy fewer than 16 × 16 pixels. Therefore, current object detection methods achieve substantially lower detection accuracy for tiny objects than for normal-scale objects. This limitation primarily arises from two critical factors: insufficient positive sample assignment and weak feature representation. To address these challenges, a Cross-Domain Collaborative Enhancement Detector (CDCEDet) is proposed. CDCEDet jointly optimizes label assignment in the spatial domain and enhances feature representation in the frequency domain, thereby improving the accuracy and robustness of tiny object detection in RSIs. Methods The overall framework of CDCEDet is illustrated in Fig. 2 and consists of three major components. First, a Scale-Adaptive Anchor Generator (SAAG) is designed to dynamically generate anchors that match the scales of ground-truth (GT) objects, thereby effectively alleviating the scale mismatch between anchors and tiny objects that has been largely overlooked in previous studies. Compared with conventional uniformly distributed anchor generators, SAAG substantially increases the number of positive samples assigned to tiny objects, even under Intersection over Union (IoU)-based label assignment. Second, a Quantile-based Adaptive Label Assignment (QALA) mechanism is developed to replace the conventional fixed IoU threshold-based label assignment. QALA models the IoU distribution between each GT object and its matched anchors to generate an adaptive label assignment threshold for each object, thereby further increasing the number of positive samples assigned to tiny objects. Third, a Frequency-Adaptive Fusion (FAF) module is developed to enhance feature representation from a frequency-domain perspective. An adaptive high-pass filter is used to strengthen high-frequency details and compensate for information loss caused by channel compression, whereas an adaptive low-pass filter preserves semantic consistency during feature upsampling, thereby reducing semantic inconsistency within upsampled objects.Results and Discussions Extensive experiments are conducted on two public remote sensing tiny object detection datasets, AI-TODv2 and AI-TOD-R. The proposed method is compared with several state-of-the-art methods, including RFLA, DCNet, and DCFL. On the AI-TODv2 dataset ( Table 1 ), CDCEDet improves AP50 and AP50–95 by 1.8% and 0.7%, respectively, compared with the best existing method. On the AI-TOD-R dataset (Table 2 ), AP50 and AP50–95 are improved by 2.6% and 0.7%, respectively. These results demonstrate that CDCEDet achieves superior detection performance and strong generalization capability for tiny object detection in RSIs. Ablation studies and parameter analyses of the proposed modules (Tables 3 –6 ) further verify the effectiveness of each component and their complementary contributions. Qualitative results on both datasets (Fig. 3 ) show that the proposed method accurately detects tiny objects in both sparse and dense scenes. As illustrated in Fig. 4, SAAG generates scale-matched anchors for individual objects and assigns substantially more positive samples to tiny objects than the conventional uniformly distributed anchor generator. Furthermore, visual comparisons with RFLA and DCNet (Fig. 5 ) demonstrate that CDCEDet achieves higher detection accuracy while substantially reducing missed detections.Conclusions A CDCEDet is proposed to address insufficient positive sample assignment and weak feature representation in remote sensing tiny object detection. Specifically, SAAG dynamically generates anchors that match the scales of GT objects, substantially increasing the number of positive samples assigned to tiny objects. QALA further improves label assignment by modeling the IoU distribution between GT objects and their matched anchors to adaptively determine the label assignment threshold, thereby effectively reducing the scale bias introduced by fixed IoU thresholds. In addition, FAF enhances feature representation from a frequency-domain perspective through an adaptive high-pass filter and an adaptive low-pass filter. Experimental results on two benchmark datasets demonstrate the superior detection performance and strong generalization capability of CDCEDet. Future work will focus on improving model efficiency and real-time performance to facilitate practical deployment in remote sensing applications. -
表 1 AI-TODv2数据集上不同算法的对比实验结果
方法 AP50-95 AP50 AP75 APvt APt APs APm Faster R-CNN*[11] 12.8 29.9 9.4 0 9.2 24.6 37.0 FSANet*[9] 17.6 45.0 10.5 5.4 15.8 22.9 33.8 LTDNet[16] 18.9 46.7 12.1 5.3 17.7 24.2 34.3 NWD[3] 21.4 53.2 12.5 7.7 20.7 26.8 35.2 MENet*[17] 21.5 52.7 13.6 8.4 21.6 25.4 33.4 ADAS-GPM[3] 22.3 53.7 13.5 7.1 21.9 27.5 35.1 RFLA*[4] 22.9 55.7 14.7 8.5 22.4 28.7 36.4 DCEDet[18] 23.5 53.9 16.8 8.5 24.1 28.2 37.1 DCNet[19] 23.6 56.3 15.7 7.6 23.6 28.6 36.4 PGDP[20] 23.9 55.8 16.6 7.3 23.5 29.0 - CDCEDet(本文方法) 24.6 58.1 16.4 10.5 24.3 29.4 38.1 注:*表示基于官方代码复现结果,粗体表示最优结果,下划线表示次优结果 表 2 AI-TOD-R数据集上不同算法的对比实验结果
方法 AP50-95 AP50 AP75 APvt APt APs APm RoI Transformer*[21] 12.3 35.3 5.5 1.3 10.6 19.7 24.5 Oriented R-CNN[22] 11.2 33.2 4.3 0.6 9.1 19.5 23.2 ReDet[23] 11.6 32.8 4.8 1.4 9.5 19.4 23.2 Oriented RepPoints[24] 13.0 40.3 4.2 5.2 12.2 16.8 21.4 ARS-DETR[25] 14.3 41.1 5.8 6.3 14.5 17.6 18.7 NWD*[3] 15.4 46.9 5.4 5.9 14.2 20.4 24.4 RFLA* [4] 16.0 48.2 5.6 5.9 14.8 20.1 24.1 DCFL[13] 15.7 47.0 5.8 6.3 14.8 19.6 22.4 CDCEDet(本文方法) 16.7 50.8 5.7 6.8 15.7 21.6 25.3 注:*表示基于官方代码复现结果,粗体表示最优结果,下划线表示次优结果 表 3 本文提出各个模块的消融实验结果
SAAG QALA FAF AP50-95 AP50 AP75 APvt APt APs APm 参数量 GFLOPs FPS 12.6 29.5 8.8 0.0 8.4 25.6 37.1 41.16M 144.09 54.8 √ 22.6 53.9 15.3 7.4 22.3 28.1 37.7 41.75M 144.18 45.0 √ √ 23.6 56.1 15.8 9.3 23.1 29.0 37.0 41.75M 144.18 44.6 √ 14.0 32.5 9.8 0.0 10.6 26.4 37.8 47.31M 155.34 48.4 √ √ √ 24.6 58.1 16.4 10.5 24.3 29.4 38.1 47.90M 155.43 40.5 表 4 QALA机制中初始分位数阈值参数$ {a}_{0} $敏感性分析
$ {a}_{0} $ AP50-95 APvt APt APs APm - 22.6 7.4 22.3 28.1 37.7 0.95 23.0 8.9 22.9 28.3 36.9 0.85 23.2 8.9 22.6 28.7 36.7 0.75 23.1 8.8 22.5 28.4 36.9 0.5 22.8 8.3 22.6 28.0 36.3 0.3 22.5 7.3 22.5 28.1 35.9 0.1 22.1 6.9 22.1 27.2 35.4 表 5 QALA机制中分位数变化范围参数$ {a}_{1} $敏感性分析
$ {a}_{1} $ AP50-95 APvt APt APs APm 0 23.2 8.9 22.6 28.7 36.7 0.1 23.6 9.3 23.1 29.0 37.0 0.3 23.0 8.4 22.9 27.9 36.6 0.5 22.8 8.3 22.8 28.8 36.0 0.7 22.8 8.5 22.4 28.4 35.6 表 6 不同滤波器核尺寸配置下的FAF模块消融实验结果
滤波器核尺寸 AP50-95 APvt APt APs APm 高通 低通 $ \hat{K}=3 $ $ \overline{K}=3 $ 24.3 9.1 24.1 29.2 37.6 $ \hat{K}=5 $ $ \overline{K}=3 $ 24.4 9.5 24.6 29.1 37.7 $ \hat{K}=5 $ $ \overline{K}=5 $ 24.2 9.0 24.6 28.7 37.3 $ \hat{K}=3 $ $ \overline{K}=5 $ 24.6 10.5 24.3 29.4 38.1 -
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