Abstract
Classification of land cover using satellite images was a major area for the past few years. A raise in the quantity of data obtained by satellite image systems insists on the requirement for an automated tool for classification. Satellite images demonstrate temporal or/and spatial dependencies, where the traditional artificial intelligence approaches do not succeed to execute well. Hence, the suggested approach utilizes a brand-new framework for classifying land cover Histogram Linearisation is first carried out throughout pre-processing. The features are then retrieved, including spectral and spatial features. Additionally, the generated features are merged throughout the feature fusion process. Finally, at the classification phase, an optimized Long Short-Term Memory (LSTM) and Deep Belief Network (DBN) are introduced that portrays classified results in a precise way. Especially, the Opposition Behavior Learning based Water Wave Optimization (OBL-WWO) model is used for tuning the weights of LSTM and DBN. Atlast, many metrics illustrate the new approach’s effectiveness.
Keywords
Introduction
The Land Cover Classification System (LCCS) is a thorough, standardized a priori classification framework that was developed for mapping activities regardless of scale or mapping technique. Data regarding Land Cover is very important for active management, planning, and monitoring, and for the realistic progression of land [1, 2]. As a result, it has to turn out to be more and more noteworthy to precisely scrutinize LC for the rational growth and exploitation of urban land sources [52, 53, 54]. In recent times, owing to speedy urban growth, Land Cover data has been distorted severely in cities that were captured by satellites [3, 4]. The evolution of remote sensing sensors has magnified the availability of high-resolution images, guiding the necessity for extracting data from satellite images [5, 6, 7]. Satellite images are extensively deployed in analyzing and monitoring variations in LC, environment, and so on [8, 9, 10].
Nowadays, information captured by satellites with shorter revisit intervals is widely deployed for scrutinizing and recognizing variations in Land Cover [11, 12]. Fourier analysis is deployed for extracting constraints, which were essential for classifying Land Cover [13, 14]. Nevertheless, these constraints could not acquire variations in Land Cover with time [55, 56]. Moreover, several Machine Learning approaches like Convolutional Neural Networks (CNN), Support Vector Machine (SVM), Deep Neural Networks (DNN), etc have been widely deployed currently owing to their high classification accuracy and minimal time consumption [15, 16, 17].
For advancing the performances of the Land Cover Classification System (LCCS) with satellite images, effectually utilizing spatiotemporal heterogeneity and correlation, as well as picking the proper spatiotemporal levels, are crucial Geographic Object-Based Image Analysis (GEOBIA) was distributed for neglecting the spectral diversity of geographical objects with adequate resultants, and it performs better than other models [18]. Nevertheless, the deployment of GEOBIA for both temporal and spatial data is said to be a problem.
The legacy of the proposed paper is:
As an innovation, this paperwork establishes a new land cover classification model, in which the spatial characteristics like Local Binary Pattern (LBP) and Gray Level Co-Occurrence Matrices (GLCM), and spectral features (Normalized Difference Water Index (MNDWI), Normalized Difference Water Index (NDWI), Modified and Normalized Difference Vegetation Index (NDVI) are derived. Introduces a new feature fusion process, by which the extracted spatial and spectral features are fused. Deploys optimized Long Short-Term Memory (LSTM) and Deep Belief Networks (DBN) for accurate classification outputs. Employs a new Opposition Behavior Learning based Water Wave Optimization (OBL-WWO) model for determining the standard weights in LSTM and DBN.
The review of this paperwork is mentioned in Section 2. In Section 3, the suggested land cover classification framework is described step by step. In Section 4, a novel feature fusion approach is used to extract spatial and spectral characteristics. In Section 5, LSTM and DBN classification framework hybrid classifiers are shown. Section 6 provides an overview of the OBL-WWO optimization technique, while Sections 7 and 8 present the outcomes and recommendations.
In 2019, Chen et al. [19] suggested a novel land cover classification model that avoided the misclassification that occurred by scale effect by merging Multi-Scale CNN (MCNN). Subsequently, this work analyzed how the scaling constraint of CNN impacted the categorization accurateness and involved spatial data for pre-estimating scale constraint in per-super pixel CNN. The investigational results have shown that MCNN could efficiently evade misclassification.
In 2021, Kareem et al. [20] designed a CNN for classifying the multispectral SAT-4 images into 4 groups: barren land, grassland, trees, and others. The adopted CNN classifier learned the spatial and spectral properties of images from provided samples of ground truth. The concern of this work was 3-fold. A classification model for extraction of features along with normalization. 9 diverse designs of Convolutional Neural Networks (CNN) were constructed, and numerous experimentations were done for classifying the images. A deep perceptive of image resolution and structure was captured by altering diverse optimizers in CNN. Finally, better and more accurately predicted outcomes were obtained using the developed scheme.
In 2019, He et al. [21] suggested the latest fuzzy improbability modeling scheme for presenting the land cover pattern features and presented a modified Fuzzy Clustering technique. The adopted fuzzy improbability modeling scheme was executed in the 2 most important stages. Initially, the input segmentation unit was subjected to object-oriented symbolic modeling. Consequently, features for every type of land cover were presented in the structure of a symbolic vector that described the intra-class uncertainties and improved the separability among diverse groups. Then, type-2 fuzzy was produced for every cluster depending upon the distance of interval-valued vectors.
In 2019, Tabib et al. [22] proposed a feature-level synthesis of Synthetic Aperture Radar (SAR) images for modifying the accuracy of urban Land Cover categorization. In the adopted object-oriented approach, segmented areas were deployed for carrying out knowledge-oriented classification depending on land surface temperature, spectral associations, and SAR quality characteristics calculated in Gray Level Co-Occurrence Matrices (GLCM) space. The estimated resultants had shown the development regarding kappa and accuracy using the developed model.
In 2019, Unnikrishnan et al. [23] utilized the Near Infra Red (NIR) and red band data for classifying satellite datasets. It was done, as ND Vegetation Index (NDVI) calculation required only 2 bands (NIR and red) data, and the classes concerned in the dataset were of vegetation type. This paperwork deployed a novel Deep Learning model for 3 diverse networks by adjusting the network. The customized architecture with a condensed count of filters was tested and trained and thus it was managed to categorize the images into diverse groups. The adopted model was evaluated in opposition to extant models regarding precision, accuracy, and trainable constraints.
In 2019, Mishra et al. [24] examined the textural features of satellite images for enhancing the classification accuracy of Land Use/Land Cover (LULC). The textual characteristics were acquired from sensor data with the support of GLCM. The finest grouping of textural features was identified make use of correlation coefficients and standard deviations thereafter separability study of the LULC group depending upon a training sample. An SVM model was deployed to carry out categorization and the resultants were computed accordingly.
In 2021, He et al. [25] proposed a multi-spectral LULC technique depending on the DL model. By deploying the estimable detailed capture capability of contour let transform for obtaining the possible data, a spectral-texture classification scheme was constructed. Thus, the feature spaces merged with DL for feature extraction were enhanced. In the end, the investigation was done that substantiated the modification of the used strategy concerning accuracy.
In 2019, Jayanth et al. [26] deployed Elephant Herding Optimization (EHO) model for analyzing multispectral pixels and for determining the data of classes. While the spectral resolution of satellite images was amplified, the statistical separability among LULC groups in spectral spaces was reduced and it tends to maintain the accuracy of classification. These were mainly for each pixel and parametrical in nature. Investigational results have exposed that EHO has shown a development over Support Vector Machine (SVM).
In 2020, Mukherjee et al. [50] investigated the Indian cities of Surat and Bharuch over 20 years to know the alternate in land use, land cover, and surface temperature using data from Landsat 5 Thematic Mapper and Landsat 8 OLI/TIRS. The explorations show that both cities have gently experienced an enormous amount of expansion in the built-up area and a loss of green space in LST.
In 2021, Hong et al. [51] suggested the shared and specific feature learning (S2FL) model for land cover classification. Especially for heterogeneous data sources, S2FL can decompose multimodal RS data into modality-specific components and modality-shared, making it possible to blend information from many modalities more successfully. Extensive testing on the three datasets shows that by classifying land cover, our S2FL model performs better than the techniques in use.
The overview of traditional methods for classifying land cover is shown in Table 1. Initially, the CNN model used in [19] provides accurate classification with minimal error values. However, it needs exploration on a larger scale area. CNN approach [20] improves the accuracy with reduced vegetation loss. However, larger remote sensing datasets are not analyzed in this work. Type-2 fuzzy [21] has enhanced accuracy with lesser noise; however, local and global relations are not attained. GLCM was exploited in [22] that increased accuracy with better kappa values; however, it needs to focus on contextual information. The convNet model adopted in [23] is very much accurate and offers high precision. Nevertheless, the count of training constraints needs to be minimized. Moreover, the GLCM method was deployed in [24] that offer high spatial resolution with high accuracy. Nevertheless, it needs new schemes for the automated election of textural features. DBN method [25] ensures high accuracy and perfect mining of spatial distribution law; however, reliability needs more exploration. Besides, the EHO approach was established in [26], which provides high Producer Accuracy with high User Accuracy. Although, it should concentrate on change detection.
Review of conventional land cover classification schemes
Review of conventional land cover classification schemes
Numerous models have been focused on under land cover classification models. However, there exist frequent problems such as no consideration in large remote sensing datasets, no consideration of local and global relations, and reliability, there is a need for a new scheme for the automated selection of textural features, and training constraints ought to be minimized. Therefore, to rectify the abovementioned issues, this study develops a novel land cover classification model. The proposed model is described in the following section.
The proposed Land Cover classification method includes 4 vital phases. Initially, in pre-processing Histogram Equalization process is employed. After that, the spatial features such as LBP features
Next, the merged features are fed as input to optimized DBN and optimized LSTM that provides the final classified output. Specifically, the OBL-WWO framework assists in achieving improved classification results in a precise manner and is utilized to optimize both the weights of LSTM and DBN.
The demonstration of the created OBL-WWO-based system is shown in Fig. 1.
Demonstration for developed Land-cover classification model.
The satellite image (Im) is pre-processed initially using the HE approach, which alters the magnitude of the image to enhance variation. This method typically increases the overall contrast of many photos, mainly while the utilizable information of the image is symbolized by closer contrast values. This permits lower contrast areas to achieve high contrast.
The extracted features are then applied to the obtained image, represented by
Spatial features
Local Binary Pattern
The LBP descriptors are demonstrated with increased differentiative capacity and clarity in a variety of relative analyses [27, 28]. Moreover, the basic LBP is frequently engaged to extract the distinguished features with a specified reference pixel
Gray Level Co-Occurrence Matrices
It is established for calculating the spatial relationship amongst the pixel [29]. The succinct simplification of GLCM is mentioned in Table 2.
Features of GLCM
ND Vegetation Index (NDVI)
It [28] is “a simple graphical indicator that can be used to analyze remote sensing measurements, typically, but not necessarily, from a space platform, and assess whether the target being observed contains live green vegetation or not”. It is computed as specified in Eq. (3), in which, NIR denoted near-infrared band.
Modified Normalized Difference Water Index (MNDWI)
MNDWI uses SWIR and green bands for enhancing the open water feature and it is evaluated as in Eq. (4). It moreover lessens urbanized area features, which are often related to open water in another index.
Normalized Difference Water Index (NDWI)
NDWI is utilized for observing variations associated with water content, using NIR and green wavelength. It is evaluated as in Eq. (5).
The derived spectral features (NDVI, MNDWI as well as NDWI features) are together pointed out
The extracted spatial features and spectral features are fused before being provided to the classification stage. Let the extracted spatial features be denoted by
The optimized LSTM and DBN are then provided with the merged features as input for categorization.
LSTMs are frequently used to learn, process, and classify sequential data, as these networks are capable of learning long-term connections between time steps of data. Also, DBN classifiers have the benefit of being less computationally costly. Hence, in this work, to land cover classification the LSTM and DBN classifiers are hybridized to make the classification result more accurate.
Optimized long short-term memory classifier
It [30] includes a series of recurring LSTM cells. Three units, including “the input gate, output gate as well as forget gate,” make up every LSTM cell. Let the variables
The
In Eq. (9),
The LSTM exploits the input gate as shown in Eqs (10)–(12), which,
According to Eqs (13) and (14), the LSTM cell receives the output hidden layer from the output unit, wherein
DBN [31] comprises different layers requiring apparent together with hidden neurons. The output denoted by
The mathematical model to arrange the binary state is shown in Eqs (18) and (19), which
The illustration of energy for hidden neuron and visible
Equation (23) shows the final weight distribution after RBM training.
The RBM uses the energy function described in Eq. (24) to calculate a chance, wherein
The procedures of the DBN model are as follows.
Let the training pattern be
Solution Encoding
As previously stated, the LSTM weights represented by
Solution encoding.
The traditional WWO model [32] shows excellent solutions; although, it undergoes low accuracy. To label the disadvantages of classical WWO, upgrading is made to the suggested algorithm. Own-suggestion is accepted to be encouraging in conventional optimization algorithms [33, 34, 35, 36, 37, 38, 39, 40]. OBL-WWO [32] is deployed for resolving optimization issues. The OBL-WWO approach has many benefits, like being easy to implement, requiring fewer control parameters and population vectors, and being particularly effective at finding the best solution in a high-amplitude search space. When compared with local search optimization like hill climbing, tabu search, and global optimization algorithms like evolutionary algorithms, and memetic algorithms, the proposed OBL-WWO approach offers huge benefits and helps in fine-tuning the mass of DBN and LSTM. Therefore, influenced by the advantages of the OBL-WWO method this paper utilized OBL-WWO for land cover classification.
The fitness
The suggested method made use of the OBL paradigm, which is designed to be used with real people and its contradictions. To remain with the greatest alternative, the values, and their opposing points are thus estimated together.
Propagation
During this phase, a novel wave
The observations of all
Refraction
When determining the place following refraction, as in Eq. (36), it is done on waves involving altitudes that have been reduced to zero, wherein,
After refraction, the height
Breaking
It is done on a wave
If there are no solitary waves, then it is superior to
Simulation set up
A projected HC
Sample image of (a) water (b) vegetation (c) land for original image 1 (d) water (e) vegetation (f) land for original image 2.
Comparing created HC
Analysis of the proposed method over the existing method concerning positive measures.
Analysis of the proposed method over the existing method concerning neutral measures.
Analysis of the proposed method over the existing method concerning negative measures.
The assumption of the HC
Convergence analysis.
The statistical analysis of the approved HC
Statistical analysis
Statistical analysis
“When a binary classifier system’s discrimination threshold is changed, a Receiver Operating Characteristic (ROC) curve, a graphical representation, shows how well the algorithm can diagnose the problem”. The Region of the Curve (FPR) is yielded by the representation of the True Positive Rate (TPR) against the False Positive Rate (FPR). Figure 8 shows the ROC curve attained by the proposed HC
Analysis of the proposed model and existing models for ROC.
The new Land Cover classification method with enhanced hybrid classifiers has been developed in this article. After performing pre-processing, spatial and spectral characteristics were extracted. Through the application of upgraded LSTM and upgraded DBN, these features were then combined and further classified. Specifically, a new OBL-WWO algorithm was employed to optimize the weights of the LSTM and DBN. Finally. it was established that the advanced method was suitable to the conventional method in many ways. At 60
Footnotes
Abbreviations
Author’s Bio
