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GSD of 50% and 100% of its native GSD. |
a combined image (rather than independent low/high recon- |
structions). In this case, when the high resolution component |
is reconstructed, we do not use the low-resolution residual, |
but rather, directly reconstruct the high resolution result. The |
“Combined” entry combines the low and high resolution re- |
sults instead of treating them as separate learning objectives. |
The separate low/high resolution reconstructions obtain the |
best performance and robustness to changes in scale. |
5. Discussion |
In this section, we share observations about Scale-MAE , |
sketch our vision for future work, and discuss high-level |
questions about Scale-MAE . |
Computational complexity. Scale-MAE requires a much |
smaller decoder than vanilla MAE—instead of a decoder |
depth of eight, Scale-MAE works well with a depth of three. |
In fact, with 322.9M vs 329.5M parameters using ViT- |
Large, Scale-MAE is smaller than vanilla MAE. However, |
GPU memory usage for equal batch sizes are higher for |
Scale-MAE since we reconstruct a higher resolution image |
in the Scale-MAE Decoder. |
Multi-spectrality and modality. Electro-optical (EO) |
satellites, such as the ones comprising the datasets mentioned |
in this work, capture light at different wavelengths. Each |
wavelength has a different sensor, and each sensor can have a |
different resolution. Scale-MAE requires input tensors to be |
stacked to pass through the model. This means that we are |
unable to use Scale-MAE when the input image’s bands are |
all of different GSDs. Additionally, synthetic aperture radar |
(SAR) imagery is another form of remote sensing where res- |
olution varies across a single band. Extending Scale-MAE |
to work with different resolution bands and modalities is |
reserved for future work. |
Can the Scale-MAE methodology be applied to other |
backbones? Methods such as ConvNeXt [42] provide |
competitive performance compared to Transformers. The |
core components of our work can be integrated, with ad- |
ditional work, into different architectures. The Laplacian |
Decoder in Scale-MAE can be engineered to ingest convo- |
Decoding Layers KNN 50% KNN 100% |
1 76.0 78.4 |
2 77.9 80.4 |
3 78.1 80.7 |
4 77.5 80.0 |
8 77.7 78.9 |
Table 8. Ablation results indicating that fewer transformer layers in |
the decoding stage tend to work better for Scale-MAE as determined |
by a KNN classification on RESISC-45 at a relative GSD of 50% |
and 100% of its native GSD. |
Low Res High Res Combined KNN 50% KNN 100% |
! 77.6 80.2 |
! 72.9 74.3 |
! 77.2 80.3 |
! ! 78.1 80.7 |
Table 9. These ablation results indicate that reconstructing both the |
low resolution and high resolution components lead to robust perfor- |
mance. Note: when the high resolution component is reconstructed, |
the low-resolution residual is not used—the high resolution result is |
directly reconstructed. The “Combined” entry merges the low and |
high resolution results instead of treating them as separate losses. |
The evaluations are a kNN classification ( k=20) on RESISC-45 at |
relative GSDs 50% and 100% of its native GSD. |
lutional feature maps. Existing work on scale-aware CNNs |
can be extended to work with the Laplacian Decoder. |
Evaluating on more remote sensing datasets. The field |
of remote sensing has had a renaissance in the last five years |
with the amount of available datasets. These can be generic, |
like Functional Map of the World, to highly specific, such |
as identifying illegal airstrips in Brazil [1, 8] or identifying |
illegal fishing vessels [47]. In fact, there are so many small, |
specific remote sensing datasets that entire review papers |
are written to enumerate them [60]. We chose to focus |
datasets with properties of remote sensing that are relevant |
to multiscale representation learning. |
6. Conclusion |
Remote sensing imagery has accelerated the rate of scien- |
tific discovery in a broad set of disciplines. With increasingly |
precise methods to extract environmental indicators using |
computer vision methods, automated understanding of re- |
motely sensed sources has become a mainstay in scientific |
literature. Remote sensing payloads are diverse and capture |
data at a wide range of resolutions, a feature heavily utilized |
by scientists. Current computer vision methods for remote |
sensing necessitate the training of a new model per input |
resolution. Not only is the training process expensive, but |
the overhead of curating a dataset at multiples scales makesthis a daunting task. |
We introduce Scale-MAE , a pretraining framework which |
introduces scale invariance into encoders that are used |
for a diverse set of downstream tasks. Our insights into |
scale-inclusive positional encodings and progressive multi- |
frequency feature extraction result in models that perform |
significantly better than state-of-the-art pretraining methods |
across (1) multiple scales and (2) many benchmarks. |
Our goal is to take the extremely diverse and rich source |
of information present in remote sensing imagery and make it |
simple to use with minimal training iterations required. With |
the introduction of Scale-MAE , we hope to further accelerate |
the rate at which scientific disciplines create impact. |
Acknowledgements |
We deeply thank Kyle Michel from Meta for providing us |