Cross-Geography Generalization of Machine Learning Methods for Classification of Flooded Regions in Aerial Images

2025-04-27 0 0 423.4KB 7 页 10玖币
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Cross-Geography Generalization of Machine
Learning Methods for Classification of Flooded
Regions in Aerial Images
Sushant Lenka
1
, Pratyush Kerhalkar
1
, Pranav Shetty
1
, Harsh Gupta
1
, Bhavam Vidyarthi
1
, and Ujjwal Verma
1, 2
1Department of Electronics and Communication Engg, Manipal Institute of Technology, Manipal Academy of
Higher Education, India
2Department of Electronics and Communication Engg, Manipal Institute of Technology Bengaluru, Manipal
Academy of Higher Education, India
Abstract
Identification of regions affected by floods is a crucial piece of information required
for better planning and management of post-disaster relief and rescue efforts.
Traditionally, remote sensing images are analysed to identify the extent of damage
caused by flooding. The data acquired from sensors onboard earth observation
satellites are analyzed to detect the flooded regions, which can be affected by low
spatial and temporal resolution. However, in recent years, the images acquired from
Unmanned Aerial Vehicles (UAVs) have also been utilized to assess post-disaster
damage. Indeed, a UAV based platform can be rapidly deployed with a customized
flight plan and minimum dependence on the ground infrastructure. This work
proposes two approaches for identifying flooded regions in UAV aerial images. The
first approach utilizes texture-based unsupervised segmentation to detect flooded
areas, while the second uses an artificial neural network on the texture features
to classify images as flooded and non-flooded. Unlike the existing works where
the models are trained and tested on images of the same geographical regions,
this work studies the performance of the proposed model in identifying flooded
regions across geographical regions. An F1-score of 0.89 is obtained using the
proposed segmentation-based approach which is higher than existing classifiers.
The robustness of the proposed approach demonstrates that it can be utilized to
identify flooded regions of any region with minimum or no user intervention.
1 Introduction and Application Context
With the increase in the frequency of occurrence of natural disasters, there is a need for better
management and planning of post-disaster relief and rescue efforts. Identification of the region
affected by the disaster is one of the crucial information required for planning post-disaster rescue
efforts. The existing method for identifying disaster-affected areas depends on images acquired from
sensors onboard Earth Observation Satellites[10] [7]. However, these images may be affected by
cloud cover and have poor spatial resolution. Besides, the longer satellite visit time may adversely
affect the post-disaster relief and rescue efforts. In recent years, images acquired from Unmanned
Aerial Vehicles have been utilized for various applications such as environment monitoring, damage
assessment etc [12] [11] [1].
For detecting the flooded areas, the aerial images are classified as flooded or non-flooded depending
on the presence/absence of flooding in the image. In this paradigm, features (Color, textures etc) are
first extracted from the images which are then fed to a classifier. In the last decade, several end-to-end
Convolutional Neural Network (CNN) based approaches have been proposed, which eliminates
36th Conference on Neural Information Processing Systems (NeurIPS 2022).
arXiv:2210.01588v1 [cs.CV] 4 Oct 2022
the need for hand-engineering the features [5]. In addition to the classification-based approach, a
few studies use the segmentation results to categorize the image as flooded or non-flooded. In this
approach, the images acquired from UAV are segmented and assigned a semantic label (flooded/non-
flooded) to each pixel in the image [2] [3] [6]. For instance, authors in [2] used Fully Convolutional
Networks (FCN) to segment the UAV images and detect the flooded regions. In separate work, in
addition to segmenting the optical UAV images, the digital elevation model was analysed to detect
the flooded region [3]. In another study, an unsupervised segmentation algorithm was utilized to
identify the flooded regions [6]. However, most existing classification and segmentation methods
for identifying the flooded regions are limited to a particular region. While [2, 3] analysed images
of flood-prone areas of North Carolina, USA, [6] analysed images acquired in Texas, USA, after
Hurricane Harvey. Extending these methods to new regions such as flood-prone regions of South Asia
would require manually annotating additional images, which is a time-consuming process. There is a
need to develop methods for detecting flooded regions that can be generalized to unseen regions with
minimum manual intervention.
The work proposes two texture features-based approaches to classify UAV aerial images as flooded or
non-flooded across different geographical regions. Indeed, the texture features of pixels corresponding
to water are different from that of other classes (Road, Buildings, greenery, etc), and, therefore can
be used to identify flooded regions. In the first approach, an artificial neural network (ANN) is
proposed in this work which distinguishes the images in texture feature space. In another approach,
a texture feature-based unsupervised segmentation is proposed to first segment the images. The
number of pixels corresponding to the flooded region is then used to classify the image as flooded
or non-flooded. The segmentation-based approach is an extension of the method proposed in [6].
A texture-based unsupervised segmentation method was proposed in [6] to assess the severity of
flooding in UAV aerial images of the same geographical region. In this work, we adapt this method to
ensure cross-geography generalization. The proposed method can be utilized to identify the flooded
region and assess the flood severity in a UAV aerial image of any region. In this work, the two
proposed methods are compared with other existing machine learning classifiers and segmentation
methods (UNet [9]) to assess the performance of the proposed methods in detecting flooded regions
across different regions.
2 Methodology
This work extends the texture-based unsupervised segmentation approach proposed in [6] for flooded
region identification for cross-geography generalization. A summary of this unsupervised segmenta-
tion approach is presented in Section 2.1. In addition, this work proposes a neural network-based
approach to identify flooded regions (Section 2.2 ).
2.1 Texture Based Unsupervised Segmentation
The input image is first segmented into different regions using k-means segmentation. The segmen-
tation is based on color (LAB color space) and texture information (Local Binary Pattern (LBP)).
Including texture features ensure a more robust identification of regions covered with water. Indeed,
pixels representing water have a distinctive texture appearance compared to other regions (roads,
buildings, etc). The segmented region does not indicate which of the
k
regions represent the flooded
area. Therefore, each
k
regions are compared with a reference flooded region using the histogram of
Local Binary Pattern features. Subsequently, the input image is categorized as flooded or non-flooded
based on the number of pixels corresponding to the flooded region. In [6], the reference flooded
the region and the input image were acquired in the same region. However, this work utilizes the
reference flooded image of a completely different region. The use of the unsupervised segmentation
approach along with reference images of a different region ensures that the proposed approach can be
adapted to identify the flooded area of any region with minimum user supervision.
2.2 Artificial Neural Network
A customized Neural Network is proposed in this work for identifying the flooded regions in UAV
aerial images. The input to the neural network is Local Binary Pattern (LBP) computed on the input
image. Using LBP features instead of gray-scale or color intensities ensures that the network learns
the texture pattern of the input image. The network consists of a sequence of seven dense layers
2
摘要:

Cross-GeographyGeneralizationofMachineLearningMethodsforClassicationofFloodedRegionsinAerialImagesSushantLenka1,PratyushKerhalkar1,PranavShetty1,HarshGupta1,BhavamVidyarthi1,andUjjwalVerma1,21DepartmentofElectronicsandCommunicationEngg,ManipalInstituteofTechnology,ManipalAcademyofHigherEducation,In...

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