Component Pooling Trained Across Orientations for Few-Shot Remote Sensing Scene Classification
Authors: Bingchen Yan, Wenheng Guo, Yuye Zhou
Organizations: School of Computer Science and Information Security, Guilin University of Electronic Technology, Guilin, 541004, China · School of Information Engineering, Institute of Disaster Prevention, Langfang, 065201, China · School of Computing & Technology, Asia Pacific University of Technology & Innovation, Kuala Lumpur, 57000, Malaysia
Few-shot remote sensing scene classification (FSRSSC) aims to recognize novel scene categories from only a few labeled images. Most FSRSSC methods summarize the feature map of an image by global average pooling, which treats the few objects that define an aerial scene and the large background around them alike, and they rarely consider that aerial images have no canonical orientation. To address these issues, we propose RoCoP, a parameter-free component pooling network trained across orientations. RoCoP consists of a feature extractor, a non-negative decomposition module (NDM) and a component scoring module (CSM). NDM factorizes the local descriptors of each image into a few additive components with a deterministic initialization and a single multiplicative update, so that the positions of one object are grouped together. CSM weights each component by its activation magnitude and converts the weights into a soft mask for pooling. Because both modules are invariant to permutations of feature positions, the only rotation-sensitive part of the pipeline is the backbone, which we train to classify randomly rotated views of every image. Experiments on NWPU-RESISC45, AID and UC Merced show that component pooling and rotated-view training are complementary: together they improve a strong transfer-learning baseline by about 2.5 points in 5-way 1-shot accuracy on NWPU-RESISC45 and AID, without adding parameters at inference. Under an identical protocol, RoCoP outperforms re-implemented metric-based and task-adaptive methods, and NDM and CSM also improve existing methods when plugged into them. We further identify the regime in which the method does not apply, namely very small base sets.
Figures & tables
Figure 1. Overview of RoCoP, drawn with real NWPU-RESISC45 images and the outputs of the trained model. (a) Base training on base classes: an image and a rotated copy pass through a shared ResNet-12; NDM factorizes the 8×8×640 feature map into r=5 components ( A1 – A5 , overlaid on the image), CSM scores each component by its mean descriptor norm and scales the scores within the image, and the resulting mask M pools the descriptors for a linear classifier trained on both views. (b) Few-shot test on novel classes (5-way 1-shot shown): the frozen backbone, NDM and CSM encode the support images and the query (masks overlaid), and a logistic regression trained on the support vectors predicts the class of the query (bars: class probabilities; red: prediction). No parameters are added at test time.
Method
Backbone
NWPU-RESISC45
UC Merced
AID
Source
ProtoNet [ 8 ]
ResNet-12
64.52 / 81.95
53.15 / 71.54
67.08 / 82.44
re-impl. in [ 30 ]
DeepEMD [ 16 ]
ResNet-12
67.50 / 80.54
52.11 / 69.82
63.78 / 80.26
re-impl. in [ 30 ]
FRN [ 17 ]
ResNet-12
66.31 / 79.67
51.14 / 65.46
66.97 / 78.82
re-impl. in [ 30 ]
DeepBDC [ 21 ]
ResNet-12
68.84 / 84.12
54.20 / 71.94
66.56 / 84.15
re-impl. in [ 30 ]
PSM [ 20 ]
ResNet-12
66.17 / 83.03
54.35 / 71.86
68.89 / 83.75
re-impl. in [ 30 ]
PA-SRM
ResNet-12
72.65 / 83.64
60.79 / 78.64
68.75 / 81.47
as quoted in [ 42 ]
Table 1. 5-way accuracy (%) reported in the literature and ours (1-shot / 5-shot). The Source column gives the paper from which the numbers are taken: “re-impl. in” marks ResNet-12 re-implementations reported by [ 30 ] . Settings differ across papers; the table is a reference, not a ranking.
Method
NWPU-RESISC45
AID
ProtoNet [ 8 ]
66.12 / 82.05
69.54 / 84.21
ProtoNet + NDM + CSM (plug-in)
66.94 / 82.63
70.41 / 85.02
Δ (paired)
+0.82 / +0.58
+0.87 / +0.81
FEAT [ 18 ]
70.38 / 85.47
73.86 / 87.52
FRN [ 17 ]
68.74 / 84.36
72.15 / 86.28
DeepEMD [ 16 ]
67.43 / 82.71
71.08 / 85.34
Table 2. Same-protocol comparison (5-way test accuracy, %, 1-shot / 5-shot, one training seed, the same 2000 episodes). Δ : difference to the row above, the same episodes. ‡ Paired 95% interval excludes 0 (Sec. 4.4 ).
LR (default)
Proto.
Config
Pooling
Rot.
Mask loss
1-shot
5-shot
1-shot
5-shot
A
GAP
–
–
69.19 ± 0.46
85.44 ± 0.26
67.83 ± 0.47
84.45 ± 0.26
B
position-wise
–
–
70.25 ± 0.46
85.77 ± 0.26
69.11 ± 0.47
84.79 ± 0.27
C
NDM+CSM
–
–
69.85 ± 0.45
86.00 ± 0.25
68.58 ± 0.46
84.66 ± 0.26
D
GAP
✓
–
70.33 ± 0.45
86.30 ± 0.24
69.04 ± 0.47
85.21 ± 0.25
I
position-wise
✓
–
71.86 ± 0.45
86.80 ± 0.24
70.77 ± 0.47
85.89 ± 0.24
Table 3. NWPU-RESISC45 test classes, 5-way accuracy (%) ± 95% episode interval, one training seed, with logistic regression (LR) and with the mask-weighted prototype classifier (Proto.).
LR (default)
Proto.
Comparison
Question
1-shot
5-shot
1-shot
5-shot
E − A
RoCoP vs. GAP
+2.51 [+2.23, +2.79]
+1.73 [+1.56, +1.89]
+2.86 [+2.57, +3.14]
+1.67 [+1.49, +1.85]
D − A
rotated views, GAP
+1.14 [+0.91, +1.36]
+0.86 [+0.71, +1.01]
+1.21 [+0.98, +1.44]
+0.76 [+0.60, +0.91]
C − A
NDM+CSM, no rotated views
+0.66 [+0.38, +0.94]
+0.57 [+0.39, +0.74]
+0.75 [+0.47, +1.03]
+0.21 [+0.02, +0.39]
E − D
NDM+CSM, with rotated views
+1.37 [+1.09, +1.66]
+0.86 [+0.70, +1.03]
+1.65 [+1.36, +1.94]
+0.92 [+0.74, +1.09]
(E − D) − (C − A)
interaction
+0.72 [+0.39, +1.04]
+0.30 [+0.09, +0.50]
+0.90 [+0.57, +1.23]
+0.71 [+0.49, +0.92]
Table 4. Paired differences on the same 2000 NWPU-RESISC45 episodes (points, 95% interval).
Figure 2. Per-class 1-shot accuracy gain of RoCoP over GAP on the NWPU-RESISC45 test classes (2000 episodes, logistic regression). A real test image of each class is shown under its bar (one image per class, fixed random seed).
Table 5. Per-image versus support-level calibration of the weights on NWPU-RESISC45 (5-way test accuracy, %, 1-shot / 5-shot, same checkpoints and 2000 episodes). Δ : paired difference, support minus per image, with 95% interval.
NWPU-RESISC45 (17.5k base images)
AID ( ≈ 5k)
UC Merced (1k)
A: GAP
69.19 / 85.44
73.20 / 87.17
55.28 / 74.03
C: NDM+CSM
69.85 / 86.00
73.73 / 87.12
53.31 / 70.84
D: GAP + rotated views
70.33 / 86.30
74.39 / 88.07
56.32 / 73.79
I: position-wise + rotated views
71.86 / 86.80
74.87 / 88.10
–
E: RoCoP
71.70 / 87.16
75.73 / 88.58
53.70 / 72.31
E − A (RoCoP vs. GAP)
+2.51 / +1.73
+2.53 / +1.41
− 1.58 / − 1.72
Table 6. 5-way test accuracy (%, 1-shot / 5-shot) and paired differences (points) across datasets, one training seed, logistic regression unless stated. n.s.: 95% episode interval includes 0. ∗ : difference of the means; paired interval not computed.
Config
Rot.
Acc. drop
Vector cos.
Mask corr.
Comp. agree.
A: GAP
–
0.09 / 0.06
0.975 ± .001
–
–
C: NDM
–
0.17 / 0.11
0.968 ± .001
0.684 ± .007
0.588 ± .005
D: GAP
✓
0.07 / 0.01
0.989 ± .000
–
–
E: RoCoP
✓
− 0.04 / 0.03
0.983 ± .000
0.771 ± .006
0.663 ± .005
Table 7. Rotation behaviour on NWPU-RESISC45 test classes (1000 images × 3 rotations, 95% intervals). Drop: clean minus mean rotated accuracy, 1-shot / 5-shot.
Figure 3. Distribution over 1000 NWPU-RESISC45 test images of the correlation between the pooling mask of an image and the back-rotated mask of its 90 ∘ /180 ∘ /270 ∘ rotations (mean over the three rotations). Dashed lines: means.
r
1-shot
5-shot
Δ vs. r=5 , 1-shot
Δ vs. r=5 , 5-shot
3 †
71.28 ± 0.46
86.71 ± 0.24
− 0.42 [ − 0.65, − 0.19]
− 0.45 [ − 0.59, − 0.31]
4
71.50 ± 0.45
86.95 ± 0.24
− 0.20 [ − 0.43, 0.03]
− 0.21 [ − 0.35, − 0.07]
5
71.70 ± 0.45
87.16 ± 0.23
–
–
8
71.43 ± 0.45
86.75 ± 0.24
− 0.27 [ − 0.50, − 0.04]
− 0.41 [ − 0.55, − 0.28]
Table 8. Sensitivity to the number of components r (RoCoP, NWPU-RESISC45 test classes, 5-way, one training seed). Differences are paired over the same 2000 episodes. † Repeated run; the first run diverged (see text).
Appendix figures & tables1 asset
Supplementary material from the paper’s appendix.
Appendix
Figure 4. Pooling masks (per-image range) overlaid on NWPU-RESISC45 test images (one image per class, fixed random seed) for queries rotated by 0 ∘ /90 ∘ /180 ∘ /270 ∘ , each mask rotated back to the original frame. Left: NDM without rotated views (C). Right: RoCoP (E). Individual images vary; the population-level effect is quantified in Table 7 and Fig. 3 . The forest row shows a texture scene, where components are not separable.
Few-shot remote sensing image scene classification (FS-RSISC) aims at classifying remote sensing images with only a few labeled samples. The main challenges lie in small inter-class variances and large intra-class variances, which are the inherent property of remote sensing images. To address these challenges, we propose a transfer-based Dual Contrastive Network (DCN), which incorporates two auxiliary supervised contrastive learning branches during the training process. Specifically, one is a Context-guided Contrastive Learning (CCL) branch and the other is a Detail-guided Contrastive Learning (DCL) branch, which focus on inter-class discriminability and intra-class invariance, respectively. In the CCL branch, we first devise a Condenser Network to capture context features, and then leverage a supervised contrastive learning on top of the obtained context features to facilitate the model to learn more discriminative features. In the DCL branch, a Smelter Network is designed to highlight the significant local detail information. And then we construct a supervised contrastive learning based on the detail feature maps to fully exploit the spatial information in each map, enabling the model to concentrate on invariant detail features. Extensive experiments on four public benchmark remote sensing datasets demonstrate the competitive performance of our proposed DCN.
Zhong Ji, Liyuan Hou, Xuan Wang +2
School of Electrical and Information Engineering, Tianjin University, Tianjin 300072, China · CETC Key Laboratory of Aerospace Information Applications, Shijiazhuang, 050081, China
Few-shot segmentation asks a model to delineate a target class in a query image from only a handful of annotated examples, a setting most acute in remote sensing, where labels are scarce and the imagery departs sharply from the natural images on which vision backbones are pretrained. Prevailing approaches either train a segmenter on labelled episodes, which raises accuracy within the training distribution but binds the model to it, or reduce each class to a lossy summary of frozen features, a single prototype, a few cluster prototypes, or a discrete clustering, none of which preserves the internal structure of a multimodal class. We argue that a class is better described by a distribution than by a point, and that frozen self-supervised features already carry enough structure to estimate that distribution directly. We introduce FROST, a training-free few-shot segmenter that treats the reference foreground and background as two point clouds on the unit sphere of frozen DINOv3 features and labels each query token by a nonparametric density ratio, with a threshold the Bayes rule fixes at zero under equal priors. Because the variance of a density estimate shrinks as its sample grows, the decision sharpens as references accumulate, and every remaining quantity from the kernel bandwidth to the spatial gate is read from the support set rather than tuned. We develop FROST for overhead imagery, where a class is typically a scatter of many small and dissimilar instances that a density tracks but a lossy summary blurs. Across seventeen remote-sensing benchmarks FROST surpasses both training-free and learning-based methods, leading by 5.6 mIoU from a single annotated example and widening its lead as the support set grows, all while remaining among the smallest models compared. Code is available at https://github.com/jhpark-ai/FROST.
Remote sensing scene classification is increasingly relying on foundation models pre-trained on large-scale Earth-observation data. Moreover, transductive inference, which exploits the collective statistical structure of the entire unlabeled query set, appears to naturally match remote sensing pipelines where large images are routinely split into patches and inferred as a batch. In this work, we introduce LC-TIM (Locally Consistent Transductive Information Maximization), which extends the state-of-the-art Transductive Information Maximization for Few-Shot CLIP (TIM++) objective with a local consistency regularizer that enforces prediction agreement between each query sample and its κ nearest feature-space neighbors. The regularizer enters as a single multiplicative factor in the closed-form q-update, adding negligible computational overhead. We further propose a multi-source extension that fuses the affinity graph from multiple remote sensing foundation model, further boosting classification accuracy. To assess these methods, we establish the first comprehensive, open-source benchmark for transductive few-shot RS scene classification, evaluating LP++, TransCLIP, TIM++, and LC-TIM across ten diverse datasets, two remote sensing vision-language models, and across various few-shot settings. Our experiments show that transductive methods consistently outperform zero-shot baselines, and that LC-TIM achieves state-of-the-art accuracy, with the largest gains in the low-shot regime where neighborhood cues are most informative. Code is publicly available at: https://github.com/elkhouryk/LC-TIM