scholarly journals Innovative approach for automatic land cover information extraction from LiDAR data

2021 ◽  
Author(s):  
Nagwa Taha Hamdy El-Ashmawy
Keyword(s):  
Statistical Analysis ◽  
Land Cover ◽  
Image Classification ◽  
Point Cloud ◽  
Land Cover Classification ◽  
Large Datasets ◽  
Lidar Data ◽  
Intensity Data ◽  
Classification Techniques ◽  
Change Curve

An airborne laser scanning (ALS) system with LiDAR (Light Detection and Ranging) technology is a highly precise and accurate 3D point data acquisition technique. LiDAR technology has been extensively used in digital surface/terrain modelling (DSM/DTM), and related applications such as 3D city modelling and building extraction. The capability of LiDAR systems to record the intensity of the return laser pulse backscattered energy in addition to the range data has motivated researchers to investigate the use of LiDAR intensity data for extracting land cover information. The main goal of this research is to maximize the benefits of the use of LiDAR data independently of any external source of data for automatically extracting accurate land cover information. Several new approaches are introduced in this research: a) classifying and filling the LiDAR intensity point cloud to produce a land cover image, b) combing multiple classified data of multiple LiDAR data-strips, c) statistical analysis segmentation technique that uses the concept of the kurtosis change curve algorithm for automatic classification of LiDAR data, and d) accelerating the classification process of large datasets by partitioning the large datasets into small, manageable datasets. Applying the traditional image classification techniques on LiDAR elevation and intensity data exclusively is included. Pixel-based, object-based, and point-based classification logics are conducted, and their results are compared to reference data. The results indicated that LiDAR data (range and intensity) can independently be used in land cover classification. By applying traditional pixel-based, supervised image classification techniques, the classification results show that auxiliary layers, which are extracted from range and intensity data, can be used for land cover classification. However, applying the supervised classification techniques on the LiDAR point cloud data without converting the data into images (Point-based logic) produced more accurate land cover classification results. The experiments on the proposed classification approach using the statistical analysis segmentation technique (based on the concept of the kurtosis change curve algorithm) show that it can be used to classify LiDAR data for land cover mapping.

scholarly journals Innovative approach for automatic land cover information extraction from LiDAR data

2021 ◽  
Author(s):  
Nagwa Taha Hamdy El-Ashmawy
Keyword(s):  
Statistical Analysis ◽  
Land Cover ◽  
Image Classification ◽  
Point Cloud ◽  
Land Cover Classification ◽  
Large Datasets ◽  
Lidar Data ◽  
Intensity Data ◽  
Classification Techniques ◽  
Change Curve

An airborne laser scanning (ALS) system with LiDAR (Light Detection and Ranging) technology is a highly precise and accurate 3D point data acquisition technique. LiDAR technology has been extensively used in digital surface/terrain modelling (DSM/DTM), and related applications such as 3D city modelling and building extraction. The capability of LiDAR systems to record the intensity of the return laser pulse backscattered energy in addition to the range data has motivated researchers to investigate the use of LiDAR intensity data for extracting land cover information. The main goal of this research is to maximize the benefits of the use of LiDAR data independently of any external source of data for automatically extracting accurate land cover information. Several new approaches are introduced in this research: a) classifying and filling the LiDAR intensity point cloud to produce a land cover image, b) combing multiple classified data of multiple LiDAR data-strips, c) statistical analysis segmentation technique that uses the concept of the kurtosis change curve algorithm for automatic classification of LiDAR data, and d) accelerating the classification process of large datasets by partitioning the large datasets into small, manageable datasets. Applying the traditional image classification techniques on LiDAR elevation and intensity data exclusively is included. Pixel-based, object-based, and point-based classification logics are conducted, and their results are compared to reference data. The results indicated that LiDAR data (range and intensity) can independently be used in land cover classification. By applying traditional pixel-based, supervised image classification techniques, the classification results show that auxiliary layers, which are extracted from range and intensity data, can be used for land cover classification. However, applying the supervised classification techniques on the LiDAR point cloud data without converting the data into images (Point-based logic) produced more accurate land cover classification results. The experiments on the proposed classification approach using the statistical analysis segmentation technique (based on the concept of the kurtosis change curve algorithm) show that it can be used to classify LiDAR data for land cover mapping.

scholarly journals Radiometric correction and normalization of airborne LiDAR intensity data for land cover classification

2021 ◽  
Author(s):  
Wai Yeung Yan
Keyword(s):  
Land Cover ◽  
Laser Energy ◽  
Experimental Testing ◽  
Processing System ◽  
Land Cover Classification ◽  
Gaussian Mixture ◽  
Airborne Lidar ◽  
Lidar Data ◽  
Intensity Data ◽  
Radiometric Correction

Airborne Light Detection And Ranging (LiDAR) has been used extensively to model the topography of the Earth surface by emitting laser pulses and measuring the distance (range) between the LiDAR sensor and the illuminated object as well as the backscattered laser energy (intensity). Nowadays, airborne LiDAR systems operating in near-infrared spectrum are also gaining a high level of interest for surface classification and object recognition. Nevertheless, due to the system- and environmental- induced distortions, airborne LiDAR intensity data requires certain correction and normalization schemes to maximize the benefits from the collected data. The first part of the thesis presents a correction model for airborne LiDAR intensity data based on the radar (range) equation. To fill the gap in current research, the thesis introduces a set of correction parameters considering the attenuation due to atmospheric absorption and scattering which have not been previously considered. The thesis further derives a set of equations to compute the laser incidence angle based on the LiDAR data point cloud and GPS trajectory. In the second part of the thesis, a normalization model is proposed to adjust the radiometric misalignment amongst overlapping airborne LiDAR intensity data. The model is built upon the use of a Gaussian mixture modeling technique for fitting the intensity histogram which can then be partitioned into several sub-histograms. Finally, sub-histogram equalization is applied to calibrate the LiDAR intensity data. To evaluate the effects of the proposed methods, a LiDAR dataset covering an urban area with three different scans was used for experimental testing. The results showed that the coefficient of variance of five land cover features were significantly reduced by 70% to 82% and 33% to 80% after radiometric correction and radiometric normalization, respectively. Land cover classification was conducted on the LiDAR intensity data where accuracy improvements of up to 15% and 16.5% were found on the classification results using the radiometrically corrected intensity data, and radiometrically corrected and normalized intensity data, respectively. With the improved land cover homogeneity and classification accuracy, the effectiveness of the proposed approach was demonstrated. The outcome of the thesis fills the gap in existing airborne LiDAR research and paves the way for the future development of LiDAR data processing system.

scholarly journals Radiometric correction and normalization of airborne LiDAR intensity data for land cover classification

2021 ◽  
Author(s):  
Wai Yeung Yan
Keyword(s):  
Land Cover ◽  
Laser Energy ◽  
Experimental Testing ◽  
Processing System ◽  
Land Cover Classification ◽  
Gaussian Mixture ◽  
Airborne Lidar ◽  
Lidar Data ◽  
Intensity Data ◽  
Radiometric Correction

Airborne Light Detection And Ranging (LiDAR) has been used extensively to model the topography of the Earth surface by emitting laser pulses and measuring the distance (range) between the LiDAR sensor and the illuminated object as well as the backscattered laser energy (intensity). Nowadays, airborne LiDAR systems operating in near-infrared spectrum are also gaining a high level of interest for surface classification and object recognition. Nevertheless, due to the system- and environmental- induced distortions, airborne LiDAR intensity data requires certain correction and normalization schemes to maximize the benefits from the collected data. The first part of the thesis presents a correction model for airborne LiDAR intensity data based on the radar (range) equation. To fill the gap in current research, the thesis introduces a set of correction parameters considering the attenuation due to atmospheric absorption and scattering which have not been previously considered. The thesis further derives a set of equations to compute the laser incidence angle based on the LiDAR data point cloud and GPS trajectory. In the second part of the thesis, a normalization model is proposed to adjust the radiometric misalignment amongst overlapping airborne LiDAR intensity data. The model is built upon the use of a Gaussian mixture modeling technique for fitting the intensity histogram which can then be partitioned into several sub-histograms. Finally, sub-histogram equalization is applied to calibrate the LiDAR intensity data. To evaluate the effects of the proposed methods, a LiDAR dataset covering an urban area with three different scans was used for experimental testing. The results showed that the coefficient of variance of five land cover features were significantly reduced by 70% to 82% and 33% to 80% after radiometric correction and radiometric normalization, respectively. Land cover classification was conducted on the LiDAR intensity data where accuracy improvements of up to 15% and 16.5% were found on the classification results using the radiometrically corrected intensity data, and radiometrically corrected and normalized intensity data, respectively. With the improved land cover homogeneity and classification accuracy, the effectiveness of the proposed approach was demonstrated. The outcome of the thesis fills the gap in existing airborne LiDAR research and paves the way for the future development of LiDAR data processing system.

scholarly journals Raster Vs. Point Cloud LiDAR Data Classification

2014 ◽  
Vol XL-7 ◽  
pp. 79-83 ◽  
Author(s):  
N. El-Ashmawy ◽  
A. Shaker
Keyword(s):  
Land Cover ◽  
Point Cloud ◽  
Image Data ◽  
Data Classification ◽  
Land Cover Classification ◽  
Flying Height ◽  
Lidar Data ◽  
Urban District ◽  
Raster Image ◽  
Point Data

Airborne Laser Scanning systems with light detection and ranging (LiDAR) technology is one of the fast and accurate 3D point data acquisition techniques. Generating accurate digital terrain and/or surface models (DTM/DSM) is the main application of collecting LiDAR range data. Recently, LiDAR range and intensity data have been used for land cover classification applications. Data range and Intensity, (strength of the backscattered signals measured by the LiDAR systems), are affected by the flying height, the ground elevation, scanning angle and the physical characteristics of the objects surface. These effects may lead to uneven distribution of point cloud or some gaps that may affect the classification process. Researchers have investigated the conversion of LiDAR range point data to raster image for terrain modelling. Interpolation techniques have been used to achieve the best representation of surfaces, and to fill the gaps between the LiDAR footprints. Interpolation methods are also investigated to generate LiDAR range and intensity image data for land cover classification applications. In this paper, different approach has been followed to classifying the LiDAR data (range and intensity) for land cover mapping. The methodology relies on the classification of the point cloud data based on their range and intensity and then converted the classified points into raster image. The gaps in the data are filled based on the classes of the nearest neighbour. Land cover maps are produced using two approaches using: (a) the conventional raster image data based on point interpolation; and (b) the proposed point data classification. A study area covering an urban district in Burnaby, British Colombia, Canada, is selected to compare the results of the two approaches. Five different land cover classes can be distinguished in that area: buildings, roads and parking areas, trees, low vegetation (grass), and bare soil. The results show that an improvement of around 10 % in the classification results can be achieved by using the proposed approach.

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