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choices; additional ablations are presented in the supple- |
mentary material. Overall, we find that the order of factor- |
ization is the most important design choice in our proposed |
framework. Using a spatio-temporal factorization from |
the video recognition literature performs poorly at 48.8% |
mIoU. Changing the factorization order to temporo-spatial |
raises performance by an absolute +29.7%to78.5%mIoU. |
Including additional clstokens increases performance to |
83.6%mIoU ( +5.1%), so we proceed with using Kclsto- |
kens in our design. We test the effect of our date-specific |
position encodings compared to a fixed set of values and |
find a significant −2.8%performance drop from using fixed |
sizePTcompared to our proposed lookup encodings. Fur- |
ther analysis is provided in the supplementary material. As |
discussed in section 3.4 our spatial encoder blocks cross cls- |
token interactions . Allowing interactions among all tokens |
comes at a significant increase in compute cost, O(K2)to |
O(K), and is found to decrease performance by −2.1% |
mIoU. Finally, we find that smaller patch sizes generally |
work better, which is reasonable given that tokens retain a |
higher degree of spatial granularity and are used to predict |
smaller regions. Using 2×2patches raises performance by |
+1.2%mIoU to 84.8%compared to 3×3patches. Our fi- |
nal design which is used in the main experiments presented |
10424 |
Germany [47] PASTIS [14] T31TFM-1618 [60] |
Model #params. (M) IT (ms) Semantic segmentation (OA / mIoU) |
BiCGRU [47] 4.5 38.6 91.3 / 72.3 80.5 / 56.2 88.6 / 57.7 |
FPN-CLSTM [7] 1.2 19.5 91.8 / 73.7 81.9 / 59.5 88.4 / 57.8 |
UNET3D [45] 6.2 11.2 92.4 / 75.2 82.3 / 60.4 88.4 / 57.6 |
UNET3Df [60] 7.2 19.7 92.4 / 75.4 82.1 / 60.2 88.6 / 57.7 |
UNET2D-CLSTM [45] 2.3 35.5 92.9 / 76.2 82.7 / 60.7 89.0 / 58.8 |
U-TAE [14] 1.1 8.8 93.1 / 77.1 82.9 / 62.4 (83.2 / 63.1) 88.9 / 58.5 |
TSViT (ours) 1.7 11.8 95.0 / 84.8 83.4 / 65.1 (83.4 / 65.4) 90.3 / 63.1 |
Model #params. (M) IT (ms) Object classification (OA / mAcc) |
TempCNN∗[40] 0.9 0.5 89.8 / 78.4 84.8 / 69.1 84.7 / 62.6 |
DuPLo∗[24] 5.2 2.9 93.1 / 82.2 84.8 / 69.4 83.9 / 69.5 |
Transformer∗[48] 18.9 4.3 92.4 / 84.3 84.4 / 68.1 84.3 / 71.4 |
UNET3D [45] 6.2 11.2 92.7 / 83.9 84.8 / 70.2 84.8 / 71.4 |
UNET2D-CLSTM [45] 2.3 35.5 93.0 / 84.0 84.7 / 70.3 84.7 / 71.6 |
U-TAE [14] 1.1 8.8 92.6 / 83.7 84.9 / 71.8 84.8 / 71.7 |
TSViT (ours) 1.7 11.8 94.7 / 88.1 87.1 / 75.5 87.8 / 74.2 |
Table 2. Comparison with state-of-the-art models from literature .(top) Semantic segmentation. (bottom) Object classification.∗1D |
temporal only models. For each model we note its number of parameters ( #params. ×106) and inference time (IT) for a single sample |
with T=52, H,W=24 and C=13 size input on a Nvidia Titan Xp gpu. We report overall accuracy (OA), mean intersection over union (mIoU) |
and mean accuracy (mAcc). For PASTIS we report results for fold-1 only; average test set performance across all five folds is shown in |
parenthesis for direct comparison with [14]. |
Figure 5. Visualization of predictions in Germany. The back- |
ground class is shown in black, ”x” indicates a false prediction. |
in Table 2 employs a temporo-spatial design with Kclsto- |
kens, acquisition-time-specific position encodings, 2×2in- |
put patches and four layers for both encoders. |
4.3. Comparison with SOTA |
In Table 2 and Fig.1, we compare the performance of |
TSViT with state-of-the-art models presented in section 2. |
For semantic segmentation, we find that all models from |
literature perform similarly, with the BiCGRU being over- |
all the worst performer, matching CNN-based architectures |
only in T31TFM-1618. For all datasets, TSViT outperforms |
previously suggested approaches by a very large margin. A |
visualization of predictions in Germany for the top-3 per-formers is shown in Fig.5. In object classification, we ob- |
serve that 1D temporal models are generally outperformed |
by spatio-temporal models, with the exception of the Trans- |
former [48]. Again, TSViT trained for classification consis- |
tently outperforms all other approaches by a large margin |
across all datasets. In both tasks, we find smaller improve- |
ments for the pixel-averaged compared to class-averaged |
metrics, which is reasonable given the large class imbalance |
that characterizes the datasets. |
5. Conclusion |
In this paper we proposed TSViT, which is the first |
fully-attentional architecture for general SITS processing. |
Overall, TSViT has been shown to significantly outperform |
state-of-the-art models in three publicly available land cover |
recognition datasets, while being comparable to other mod- |
els in terms of the number of parameters and inference time. |
However, our method is limited by its quadratic complexity |
with respect to the input size, which can lead to increased |
hardware requirements when working with larger inputs. |
While this may not pose a significant issue for semantic seg- |
mentation or SITS classification, it can present challenges |
for detection tasks that require isolating large objects, thus |
limiting its application. Future research is needed to address |
this limitation and enable TSViT to scale more effectively |
to larger inputs. |
Acknowledgements MT and EC acknowledge funding |
from the European Union’s Climate-KIC ARISE grant. SZ |
was partially funded by the EPSRC Fellowship DEFORM: |
Large Scale Shape Analysis of Deformable Models of Hu- |
mans (EP/S010203/1). |
10425 |
References |
[1] European Space Agency. The sentinel missions. https:// |
www.esa.int/Applications/Observing_the_ |
Earth/Copernicus/The_Sentinel_missions . |
Accessed: 2022-11-11. 1 |
[2] European Space Agency. Sentinels for common agriculture |
policy. http://esa-sen4cap.org/ . Accessed: 2022- |
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