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with every other embedded instance in the training set. The |
instance is classified correctly if the majority of its k-nearest- |
neighbors are in the same class as the validation instance, |
and incorrectly if they are in any other. |
The reasoning behind the kNN classifier evaluation is |
that a strong pretrained network will output semantically |
grouped representation for unseen data of the same class. |
This evaluation for the quality of representations occurs in |
other notable works [7, 9, 57]. In addition to using evalua- |
tion datasets at different GSDs, to further test the multiscale |
representations, we create multiple test sets for each dataset. |
Since we cannot synthesize data at a finer GSD than the |
provided ground truth, we only downsample the full reso- |
lution validation set to coarser GSDs at fixed percentages: |
XG% |
val, Gβ {12.5,25,50,100}. |
Our analysis uses eight different land-use classification |
datasets: RESISC-45 [11], the UC Merced Land Use Dataset |
[65], AiRound and CV-BrCT [43], MLRSNet [48], EuroSAT |
[29], Optimal-31 [55], WHU-RS19 [14], SpaceNet v1 and |
v2 [53], and Functional Map of the World [12]. The datasets |
used span a wide range of GSDs, e.g., MLRSNet consists of |
data captured from aerial platforms with 0.1m GSD, while |
RESISC45 has imagery from medium-resolution satellites |
at>30m GSD. In some cases, the datasets present imagery |
at mixed GSDs which are not specified, in which case we as- |
sume an approximate constant GSD: see the supplementary |
material for all details. Furthermore, we provide an expanded |
set of experiments with linear probing and finetuning in the |
supplementary material.Average Accuracy (%) |
Dataset Scale-MAE SatMAE ConvMAE |
AiRound 63.2 57.8 59.7 |
CV-BrCT 69.7 66.2 68.4 |
EuroSAT 86.7 84.4 88.8 |
MLRSNet 81.7 75.0 79.5 |
OPTIMAL-31 65.5 55.7 61.7 |
RESISC 70.0 61.0 67.0 |
UC Merced 75.0 69.8 70.0 |
WHU-RS19 79.5 78.5 77.0 |
Table 1. Scale-MAE performs better, across all GSDs (as in Fig- |
ure 5), for all datasets we experimented with compared to SatMAE. |
The average improvement across all datasets for Scale-MAE com- |
pared to SatMAE is 5.6% and 2.4% compared to ConvMAE with |
ViT-Large backbones. |
We run kNN classification with k= 20 . Figure 5 shows |
thatScale-MAE outperforms SatMAE and ConvMAE across |
GSD scales in the different evaluation datasets and across |
relative GSD scales within individual datasets. For example, |
the UC Merced has a GSD of 0.3m, but evaluating at scales |
[12.5%,100%] provides an artificial GSD range of [0.3m, |
2.4m]. On this example, we see that Scale-MAE provides |
the largest performance gap at the 2.4m GSD, with similar |
performance at 0.3m. |
Across all other evaluation datasets and wider range of |
GSDs, Scale-MAE outperforms SatMAE and ConvMAE, |
where Scale-MAE outperforms both methods by a larger gap |
as the GSD increasingly varies from the original GSD, indi- |
cating that Scale-MAE learns representations that are more |
robust to changes in scale for remote sensing imagery. We |
outperform SatMAE by an average of 5.6% and ConvMAE |
by an average of 2.4% across all resolutions and datasets (see |
Table 1). UC Merced at 100% of the true GSD is the only |
evaluation where SatMAE outperforms Scale-MAE . The |
supplementary material contains an extensive table demon- |
strating kNN classification results with varying k. |
Linear probing and finetuning We perform linear classi- |
fication on the RESISC-45 and FMoW-RGB datasets. We |
fine-tune for 50 epochs using the same hyperparameter set- |
tings as SatMAE [13]: a base learning rate of 5Γ10β3, a |
weight decay of 5Γ10β3. We do not use temporal data for |
classification. For RESISC-45, we fine-tune for 100 epochs |
with a base learning rate of 4Γ10β3, a weight decay of |
5Γ10β3, and a global batch size of 256 across 2 GPUs. The |
learning rate on the backbone is multiplied by a factor of 0.1. |
We use RandomResizedCrop for augmentation. We train on |
224x224 images and evaluate 256x256 images because we |
found evaluating at a higher scale improves the performance |
of all models. We report both the performance of end-to-end |
fine-tuning and linear probing with a frozen backbone. The |
linear probing setup was the same as finetuning except the |
learning rate was 0.1. The results are shown in Table 2 and |
Table 3. |
Model Backbone Frozen/Finetune |
Scale-MAE Vit-Large 89.6/95.7 |
SatMAE [13] Vit-Large 88.3/94.8 |
ConvMAE [21] ConvVit-Large 81.2/95.0 |
MAE [26] Vit-Large 88.9/93.3 |
Table 2. Transfer classification results on RESISC-45. Frozen |
indicates a linear probe and finetune is a full end-to-end finetuning |
of the entire model. |
Model Backbone Top-1/Top-5 |
Scale-MAE ViT-Large 77.9/94.3 |
SatMAE β [13] ViT-Large 72.4/91.9 |
MAE [26] ViT-Large 68.4/90.3 |
ConvMAE [21] ConvVit-Large 74.1/91.4 |
SatMAE β[13] ViT-Large 77.8/- |
GASSL [4] ResNet-50 71.55/- |
MoCo-V2 [27] ResNet-50 64.34/- |
Table 3. Full finetuning results on FMoW-RGB. β : We repro- |
duce SatMAE and ConvMAE by taking their publicly available |