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transformers as the backbone rather than a convolutional |
neural network and relies on a lightweight decoder for the |
downstream tasks. |
Graph-based models have been explored in [18] for building |
damage detection solutions to capture similarities between |
neighboring buildings for predicting the damage. They used |
the xBD dataset for cross-disaster generalization. While their |
proposed approach showed some advantages in terms of |
accuracy, it did not consistently outperform the Siamese |
CNN model in terms of F1 score, which would be a more |
appropriate metric for imbalanced datasets. Furthermore, [19] |
proposed BLDNet based on a Siamese CNN combined with |
a graph node classification approach to be trained in a semi- |
supervised manner to reduce the number of labeled samples |
needed to obtain new predictions. They benchmarked their |
approach with a semi-supervised multiresolution autoencoder |
and showed performance improvements. The extremely |
imbalanced distributions of the building damages are |
addressed in [20] by supplementing the architecture with a new |
learning strategy comprising normality-imposed data-subset |
generation and incremental training. However, they propose |
a two-step solution approach for building localization and |
damage classification. Self-supervised comparative learning |
approach has been studied in [21] to address the task without |
the requirement of labeled data. Their proposed approach is an |
asymmetric twin network architecture evaluated on the xBD |
dataset. |
In this study, we propose a Siamese approach inspired by |
[4], [5] where UNet architecture is used for the building |
segmentation task and UNet’s encoders with shared parameters |
for pre-disaster and post-disaster imagery, are used to |
score building damage levels via an end-to-end approach. |
Furthermore, we also evaluate the performance of our model |
in various scenarios that resemble operational emergency |
conditions. Web visualizer tools have been developed for |
other specific domains like data-driven wildfire modeling |
[22] and fire inspection prioritization [23] in the past. Our |
developed web visualizer allows imagery and prediction layers |
visualization for any disasters where before and after disaster |
satellite images are available. |
III. D ATA |
In this study, we use the xBD dataset introduced in [24] |
as a new large-scale dataset for the advancement of change |
detection and building damage assessment for humanitarian |
assistance and disaster recovery research. This dataset has been |
sourced from the Maxar/DigitalGlobe Open Data Program. It |
covers 19 different disasters from around the world for which |
there exists high-resolution ( <0.8m/px resolution) imagery. |
The disaster types include flood, wind, fire, earthquake, |
tsunami, and volcano. The entire dataset contains 22,068 |
image tiles of 1024 ×1024 pixels that cover a total of 45,361.79 |
sq. km. There are 850,736 building polygons available along |
with a damage level label that indicates: no-damage, minor- |
damage, major-damage, and destroyed. The breakdown of the |
number of polygons for pre-disaster images across different |
disasters is shown in Table I. Figure 1 and Figure 2 show |
some examples of pre- and post-disaster image frames from |
the xBD dataset. See figure 5 for legend. |
Name/Location Type # of polygons |
Palu, Indonesia Earthquake/Tsunami 55,789 |
Mexico City, Mexico Earthquake/Tsunami 51,473 |
Nepal Flood 43,265 |
Hurricane Harvey, USA Flood 37,955 |
Hurricane Michael, USA Wind 35,501 |
Hurricane Matthew, USA Wind 23,964 |
Portugal Wildfire 23,413 |
Moore, OK Wind 22,958 |
Santa Rosa, CA Wildfire 21,955 |
SoCal, CA Wildfire 18,969 |
Sunda Strait, Indonesia Earthquake/Tsunami 16,847 |
Joplin, MO Wind 15,352 |
Tuscaloosa, AL Wind 15,006 |
Midwest USA Flood 13,896 |
Hurricane Florence, USA Flood 11,548 |
Woolsey, CA Wildfire 7,015 |
Pinery, Australia Wildfire 5,961 |
Lower Puna, HI V olcanic eruption 3,410 |
Guatemala V olcanic eruption 991 |
TABLE I |
DISASTER EVENTS IN THE X BD DATASET . |
IV. M ODEL ARCHITECTURE |
We propose a deep learning model that conducts both |
building segmentation and damage classification tasks via |
a single pipeline. Our approach has some similarities to |
the proposed method in [5]. However, our architecture |
is less complex as we do not incorporate any attention |
Fig. 1. Imagery samples from different disasters from DigitalGlobe. |
(a) Pre-disaster |
(b) Post-disaster |
(c) Ground Truth |
Fig. 2. Imagery samples with polygons showing building edges and colors |
showing damage level. |
layers in the model. One module of our model is based |
on the UNet architecture proposed in [25], which obtains |
the building segmentation mask. A single image frame is |
fed to the fully convolutional UNet model where local |
information is captured via encoder-decoder structures and |
global information is captured via several skip connections. |
In the damage assessment scenario, we have a pair of pre- |
and post-disaster image frames, which are given as inputs |
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