In the realm of landslide risk assessment, the development of a comprehensive system is imperative for proactive disaster management. This multifaceted system comprises several key components, commencing with data collection and preprocessing to gather pertinent information encompassing slope, elevation, precipitation, soil type, and rainfall in landslide-prone regions. Subsequently, we delve into algorithm selection and training, where four diverse machine learning algorithms - Convolutional Neural Network (CNN), Random Forest, Logistic Regression, and Support Vector Machine (SVM) - are harnessed to predict landslide susceptibility. The system incorporates a real-time map interface, utilizing web-based mapping libraries like Leaflet, allowing user interaction to select specific locations. Further, the chosen features are extracted, undergo thorough preprocessing, and are passed to the trained algorithms for predicting landslide susceptibility probabilities. The system's evolution continues through iterative testing and optimization, with a user-centric approach aiming to enhance the interface's usability and interpretability. Upon achieving an optimal design, the system is deployed on a server or platform, with provisions for regular model updates in response to new data or changing conditions. Lastly, the system's performance is comprehensively evaluated in real-world scenarios, encompassing algorithmic comparisons and usability assessments.
2.1 Convolutional Neural Network (CNN)
Among the deep learning algorithm there is a class called convolutional neural networks, or CNNs.
It is widely used for image processing and pattern prediction. They excel in capturing spatial relationships within images.The expanded form of artificial neural networks, recognised as convolutional neural networks (CNNs), is primarily used to extract features from grid-like matrix datasets. For instance, visual datasets with a lot of data patterns, such pictures or movies.
CNN architecture:
A convolutional neural network is composed of several layers, including the input layer, pooling layer, convolutional layer, and fully connected layer. A simple CNN architecture is shown in Fig. 1.
Features are taken from the input image by applying filters, and the final prediction is produced by the connected layer. The network finds the optimal filters through gradient descent and backpropagation. While CNNs are commonly used for image analysis, their application to landslide prediction involves converting geospatial data into image-like formats. For instance, elevation data can be represented as grayscale images, allowing CNNs to learn intricate spatial patterns related to landslide susceptibility.
Strengths:
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- Effective in capturing complex spatial patterns.
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- Can learn features automatically through hierarchical layers.
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- Suitable for handling large and diverse datasets.
Weaknesses:
CNN Algorithm-
Convolutional, pooling, and fully connected layers are the several layers that make up the Convolutional Neural Network (CNN) architecture.
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1. Input Layer:
2. Convolutional Layer:
$$\text{Convolution operation: }{Z}^{\left[l\right]}={W}^{\left[l\right]}*{A}^{[l-1]}+{b}^{\left[l\right]}$$
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$$\text{Activation function: }{A}^{\left[l\right]}=g\left({Z}^{\left[l\right]}\right)\text{ (e.g., ReLU)}$$
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3. Pooling Layer:
- Max pooling operation:
$$\text{Max pooling operation: }{A}^{\left[l\right]}=\text{m}\text{a}\text{x}\text{p}\text{o}\text{o}\text{l}\left({Z}^{\left[l\right]}\right)$$
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4. Fully Connected Layer:
$$\text{Flatten operation: }{A}_{\text{flat }}^{\left[l\right]}=\text{ flatten }\left({A}^{\left[l\right]}\right)$$
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$$\text{Linear transformation: }{Z}^{[l+1]}={W}^{[l+1]}\cdot {A}_{\text{flat }}^{\left[l\right]}+{b}^{[l+1]}$$
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$$\text{Activation function: }{A}^{[l+1]}=g\left({Z}^{[l+1]}\right)$$
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5. Output Layer:
- Al+1 represents the final output.
Here, (l) denotes the layer index, (W) symbolizes the weight matrices, (b) embodies the bias vectors, and (g) is activation function.
2.2. Random Forest
Several decision trees are used in the Random Forest ensemble learning technique to increase prediction accuracy and reduce overfitting. Random Forest is a collective approach that can handle both classification and regression analyses. It does this by using multiple decision trees and a technique called Bootstrap and Aggregation, or bagging. The key idea here is to use a combination of decision trees instead of depending only on one to determine the final result.
Random Forest uses a number of decision trees as its basic learning models. Sample datasets is generated for every model by choosing rows and features at randomly from the dataset. We refer to this section as Bootstrap.
Random Forest can handle various types of data and is effective for capturing non-linear relationships among multiple parameters (slope, elevation, precipitation, soil type, rainfall).
Strengths:
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- Handles mixed data types and categorical features well.
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- Reduces overfitting through ensemble averaging.
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- Provides feature importance analysis.
Weaknesses:
Random Forest algorithm:
A simplified representation of the Random Forest algorithm in a high-level, equation-like form:
1. Given Training Data: (dup: 6 ?)
$$\text{Training data: }\left\{\left({x}^{\left(1\right)},{y}^{\left(1\right)}\right),\left({x}^{\left(2\right)},{y}^{\left(2\right)}\right),\dots ,\left({x}^{\left(m\right)},{y}^{\left(m\right)}\right)\right\}$$
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2. Random Forest Training:
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- For every forest tree
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- Use feature bagging, which involves selecting a subset of features at random for the tree.
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- Using replacement, randomly select a portion of the training examples (bagging or bootstrap aggregating).
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- Train a decision tree \(t\) on the sampled data.
3. Decision Function:
- For a new input, the random forest predicts the output by combining the predictions of all trees. For classification, this may involve a majority vote; for regression, it may involve averaging.
$${\widehat{y}}_{\text{new }}=\text{ CombinationFunction }\left({t}_{1}\left({x}_{\text{new }}\right),{t}_{2}\left({x}_{\text{new }}\right),\dots ,{t}_{T}\left({x}_{\text{new }}\right)\right)$$
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The combination function depends on the task (classification or regression).
4. Random Forest Classification (Majority Vote):
- For classification, the majority vote is often used:
$${\widehat{y}}_{\text{new }}=\text{m}\text{o}\text{d}\text{e}\left({t}_{1}\left({x}_{\text{new }}\right),{t}_{2}\left({x}_{\text{new }}\right),\dots ,{t}_{T}\left({x}_{\text{new }}\right)\right)$$
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5. Random Forest Regression (Averaging):
- For regression, the predictions are typically averaged:
$${\widehat{y}}_{\text{new }}=\frac{1}{T}\sum _{i=1}^{T} {t}_{i}\left({x}_{\text{new }}\right)$$
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Random Forests leverage the power of several decision trees, each trained on an alternative subset of the data, to improve generalization performance. The randomness introduced during training helps decorrelate the trees and reduce overfitting.
2.3. Logistic Regression
A linear classification procedure called logistic regression calculates the likelihood of a binary result depending on one or more predictor factors. A supervised machine learning approach called logistic regression is mostly utilized to solve classification issues in which the objective is to estimate the likelihood that a given instance will belong to a particular class. Logistic regression is the term for the classification algorithms that employ it. The reason it's called regression is that it estimates the probability for a particular class using a sigmoid function, using the output of the linear regression function as input. The output of logistic regression is a likelihood of an instance falling within a certain category, whereas the output of linear regression is a continuous value that might belongs to a given class or not.
Application to Landslide Prediction: One tool for modeling the link between predictor variables is logistic regression. (e.g., elevation, soil type) and the binary outcome of landslide susceptibility.
Strengths:
Weaknesses:
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- Assumes linear relationships, might not capture complex interactions.
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- Limited by the linear decision boundary.
Logistic Regression algorithm:
A simplified representation of the Logistic Regression algorithm in the form of equations:
1. Given Training Data: (dup: 10 ?)
$$\text{Training data: }\left\{\left({x}^{\left(1\right)},{y}^{\left(1\right)}\right),\left({x}^{\left(2\right)},{y}^{\left(2\right)}\right),\dots ,\left({x}^{\left(m\right)},{y}^{\left(m\right)}\right)\right\}$$
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2. Logistic Function (Sigmoid):
- The logistic function (sigmoid) is defined as:
$$h\left(x\right)=\frac{1}{1+{e}^{-(w\cdot x+b)}}$$
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here w is the weight vector, the bias term b is, and e is the base.
3. Hypothesis:
- The hypothesis function is given by:
$$\widehat{y}=h\left(x\right)=\frac{1}{1+{e}^{-(w\cdot x+b)}}$$
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4. Cost Function (Binary Cross-Entropy Loss):
- The cost function:
$$J(w,b)=-\frac{1}{m}\sum _{i=1}^{m} \left[{y}^{\left(i\right)}\text{l}\text{o}\text{g}\left({\widehat{y}}^{\left(i\right)}\right)+\left(1-{y}^{\left(i\right)}\right)\text{l}\text{o}\text{g}\left(1-{\widehat{y}}^{\left(i\right)}\right)\right]$$
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5. Gradient Descent (Update Rule):
$$w:=w-\alpha \frac{\partial J}{\partial w},b:=b-\alpha \frac{\partial J}{\partial b}$$
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6. Prediction:
- Given a new input, predict its class label using the hypothesis function:
$${\widehat{y}}_{\text{new }}=\frac{1}{1+{e}^{-\left(w\cdot {x}_{\text{n}\text{e}\text{w}}+b\right)}}$$
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The logistic function transforms the linear combination of input features and parameters into a value between 0 and 1, representing the probability of the positive class. The discrepancy between the actual labels and the anticipated probabilities is measured by the cost function. Gradient descent is used to minimize this cost function and find optimal parameter values.
2.4. Support Vector Machine (SVM)
It is a classification algorithm designed to determine the optimal hyperplane for segregating data into distinct classes while maximizing the margin between them. SVM, a supervised machine learning approach, is versatile and can handle both regression and classification tasks, although it's primarily employed for classification purposes. Its main objective lies in identifying the best hyperplane within an N-dimensional space in order to efficiently divide data points into various feature space classes. The goal of this hyperplane's design is to increase the distance between two points in each class. However, it gets difficult when dealing with more than three features.
Think about a dependent variable that is either a red or blue circle, and two independent variables, x1, x2.
It is rather evident from the above given Fig. 2 that there are numerous lines that divide our data points into red and blue circles (our hyperplane is a line in this case because we are just taking into account two input features, x1, x2).
SVM is useful for complex interactions among multiple parameters because it can map data into higher-dimensional spaces, which captures non-linear correlations.
Strengths:
Weaknesses:
SVM algorithm:
A simplified representation of the Support Vector Machine (SVM) algorithm in the form of equations:
1. Given Training Data:
$$\text{Training data: }\left({x}^{\left(1\right)},{y}^{\left(1\right)}\right),\left({x}^{\left(2\right)},{y}^{\left(2\right)}\right),\dots ,\left({x}^{\left(m\right)},{y}^{\left(m\right)}\right)$$
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2. Objective Function:
- Minimize the following objective function:
$$\frac{1}{2}\parallel w{\parallel }^{2}+C\sum _{i=1}^{m} max\left(\text{0,1}-{y}^{\left(i\right)}\left(w\cdot {x}^{\left(i\right)}+b\right)\right)$$
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3. Decision Function:
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4. Optimization:
5. Prediction:
- Given a new input, predict its class label using the decision function:
$$\widehat{y}=\text{s}\text{i}\text{g}\text{n}\left(w\cdot {x}_{\text{new }}+b\right)$$
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The penalty for incorrect classifications and margin maximization are combined to form the objective function. Regulating the trade-off between attaining a higher margin and permitting certain misclassifications is the regularization parameter (C).