Organizations: College of Computing and Informatics, Sungkyunkwan University, South Korea · Department of Computer Science and Engineering, University of Michigan, United States · Konkuk Aerospace Design-Airworthiness Institute, Konkuk University, Seoul, 05029, South Korea · Department of Electronic Systems, Aalborg University, 2450 København SV , Denmark · Department of Information and Communication Engineering, Noakhali Science and Technology University, Noakhali-3814, Bangladesh · Department of Electrical and Computer Engineering at the University of Houston, Houston, TX 77004 USA
Federated learning (FL) has recently become a promising solution for analyzing remote sensing satellite imagery (RSSI). However, the large scale and inherent data heterogeneity of images collected from multiple satellites, where the local data distribution of each satellite differs from the global one, present significant challenges to effective model training. To address this issue, we propose a Geometric Knowledge-Guided Federated Dual Knowledge Distillation (GK-FedDKD) framework for RSSI analysis. In our approach, each local client first distills a teacher encoder (TE) from multiple student encoders (SEs) trained with unlabeled augmented data. The TE is then connected with a shared classifier to form a teacher network (TN) that supervises the training of a new student network (SN). The intermediate representations of the TN are used to compute local covariance matrices, which are aggregated at the server to generate global geometric knowledge (GGK). This GGK is subsequently employed for local embedding augmentation to further guide SN training. We also design a novel loss function and a multi-prototype generation pipeline to stabilize the training process. Evaluation over multiple datasets showcases that the proposed GK-FedDKD approach is superior to the considered state-of-the-art baselines, e.g., the proposed approach with the Swin-T backbone surpasses previous SOTA approaches by an average 68.89% on the EuroSAT dataset.
Figures & tables
Fig. 1 : The discrepancy between local & global distribution for satellite imagery. Each satellite may have different categories and different amounts of data. Images are derived from the Satellite Image Classification (SIC) Dataset [ 5 ] .
Fig. 2 : Architecture of the proposed GK-FedDKD method, which is formed by multiple clients (i.e., satellites) and a server. This architecture showcases the specific implementation of Fig. 3 .
Fig. 3 : The overall framework of the proposed GK-FedDKD method includes: client & server parts. The client part contains: A KD with unlabeled augmented data for TE generation, B KD with labeled data and local covariance matrices calculation, C GVs-guided local embedding augmentation (LEA) and local learning regulation, D a linear layer-based module, and E multi-prototype (MP) generation strategy. The server part plays the role of 1) global covariance matrices generation, 2) model aggregation, and 3) MP aggregation.
Fig. 4 : Per-class data sample distribution across ten clients.
Fig. 5 : Data augmentation over the SIC dataset with rotation, Gaussian noise, flip, brighter, darker, saturation, and salt and pepper, respectively.
Fig. 6 : Convergence comparison among FedExP, FedAS, FedPer and the proposed GK-FedDKD method.
BB
Method
EuroSAT
SAT4
SAT6
Accuracy
AA
MFS
Accuracy
AA
MFS
Accuracy
AA
MFS
Swin-T
FedExP [ 23 ]
0.6001
0.6046
0.5877
0.5656
0.5896
0.5206
0.8875
0.8652
0.7301
MOON [ 54 ]
0.7179
0.7187
0.7016
0.3506
0.3194
0.1298
0.7335
0.7084
0.5310
FedAU [ 24 ]
0.6713
0.6785
0.6432
0.7786
0.7923
0.7731
\color[rgb]{0,0,1}{0.9240}
\color[rgb]{0,0,1}{0.8997}
\color[rgb]{0,0,1}{0.7913}
FedProto [ 13 ]
\color[rgb]{0,0,1}{0.8286}
\color[rgb]{0,0,1}{0.8281}
\color[rgb]{0,0,1}{0.8203}
\color[rgb]{0,0,1}{0.8246}
\color[rgb]{0,0,1}{0.8375}
\color[rgb]{0,0,1}{0.8130}
0.8740
0.8678
0.7495
FedProx [ 55 ]
0.2156
0.1348
0.1294
0.4992
0.5257
0.3955
0.4075
0.3247
0.2067
TABLE I : Performance comparison among the proposed GK-FedDKD and other baselines (BB: Backbone; AA: Average Accuracy; MAS: Macro-F1 Score). The highest values are shown in bold, the second best is marked in blue, and the difference between the best and the second best is depicted in red.
Dataset
Metrics
Method
FedExP [ 23 ]
MOON [ 54 ]
FedProto [ 13 ]
FedAU [ 24 ]
Ours
△
EuroSAT
Error Rate
0.3999
0.2821
\color[rgb]{0,0,1}{0.1714}
0.3287
0.0997
−0.0717
MAE
1.7178
1.1016
\color[rgb]{0,0,1}{0.6726}
1.3353
0.3710
−0.3016
SIC
Error Rate
\color[rgb]{0,0,1}{0.0966}
0.1572
0.1452
0.2406
0.0768
−0.0198
MAE
\color[rgb]{0,0,1}{0.1044}
0.1710
0.1518
0.2567
0.0840
−0.0204
SAT4
Error Rate
0.4344
0.6494
\color[rgb]{0,0,1}{0.1754}
0.2214
0.0484
−0.127
TABLE II : Error rate and mean absolute error (MAE) achieved by the proposed method and other baselines. Bold numbers denote the best values, and blue numbers represent the second best. Notably, the lower the value in this Table, the better the result.
Dataset
MPG
LL_M
GIA
TE Generation
Swin-T
Accuracy
△
EuroSAT
0.8977
−0.0026
0.8958
−0.0045
0.8974
−0.0029
0.8961
−0.0042
0.9003
−
TABLE III : Importance of critical components for the proposed method (MPG: multi-prototype generation, LL_M: linear layer-based module, GIA: global information alignment).
LR
Accuracy
FedAS
FedPer
Ours
△
0.01
0.8445
\color[rgb]{0,0,1}{0.8490}
0.9650
\color[rgb]{1,0,0}{+0.116}
0.001
0.7415
\color[rgb]{0,0,1}{0.7915}
0.9485
\color[rgb]{1,0,0}{+0.157}
0.0001
0.5155
\color[rgb]{0,0,1}{0.6860}
0.9175
\color[rgb]{1,0,0}{+0.2315}
TABLE IV : Accuracy obtained by FedAS, FedPer and the proposed GK-FedDKD approach when considering various learning rates for the SAT6 dataset. The best value is highlighted in bold, the second best is shown in blue, and the enhancement is offered in red.
Fig. 7 : The convergence curve was obtained by using the proposed GK-FedDKD approach over SAT6 dataset under the consideration of LR=0.01 and LR=0.001 .
Method
# 10
# 20
# 30
# 50
FedExP [ 23 ]
0.8875
0.8387
\color[rgb]{0,0,1}{0.9045}
\color[rgb]{0,0,1}{0.9270}
MOON [ 54 ]
0.7335
0.7521
0.7536
0.5975
FedAU [ 24 ]
\color[rgb]{0,0,1}{0.9240}
0.8280
0.6433
0.5782
FedProto [ 13 ]
0.8740
\color[rgb]{0,0,1}{0.8857}
0.8567
0.7560
FedProx [ 55 ]
0.4075
0.5726
0.7034
0.6870
FedAS [ 25 ]
0.7415
0.7746
0.5960
0.5517
TABLE V : Accuracy achieved by the proposed method and the baselines under the consideration of various numbers of clients (i.e., {10,20,30,50} ), where SAT6 dataset is adopted. The optimal values are shown in bold, and the second-best is marked in blue. The improvements between them are provided in red.
Method
Dir=0.5
Dir=50
Accuracy
AA
MFS
Accuracy
AA
MFS
FedExP [ 23 ]
0.8665
0.8397
\color[rgb]{0,0,1}{0.7564}
\color[rgb]{0,0,1}{0.9325}
\color[rgb]{0,0,1}{0.9346}
\color[rgb]{0,0,1}{0.8261}
MOON [ 54 ]
0.7595
0.7299
0.4856
0.8945
0.8940
0.7222
FedAU [ 24 ]
0.88
0.8419
0.6836
0.9320
0.9321
0.7577
FedProto [ 13 ]
\color[rgb]{0,0,1}{0.8855}
\color[rgb]{0,0,1}{0.8610}
0.7417
0.9265
0.9263
0.8252
FedProx [ 55 ]
0.5535
0.5591
0.3372
0.3490
0.3491
0.1745
TABLE VI : Performance comparison among the proposed GK-FedDKD and other baselines (AA: Average Accuracy; MAS: Macro-F1 Score) over SAT6 dataset. The largest values are depicted in bold, the second-best is highlighted in blue, and the improvement between the best and the second-best is shown in red.
Fig. 8 : Local embedding visualization for the test part of SAT6 dataset. The corresponding local embedding is generated by using the global model trained by the proposed method in round 30 .
Fig. 9 : Confusion matrix achieved by leveraging the proposed GK-FedDKD approach.
Faculty of Electrical Engineering and Computer Science, Technische Universität Berlin, 10587 Berlin, Germany · BIFOLD - Berlin Institute for the Foundations of Learning and Data, 10587 Berlin, Germany
School of Artificial Intelligence, Wuhan University, Wuhan 430072, China · School of Information Science and Engineering, Wuhan University of Science and Technology, Wuhan 430081, China · School of Computer Science, Wuhan University, Wuhan 430072, China