- 标题
- 摘要
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- 实验方案
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An Improved Top-Hat Filter with Sloped Brim for Extracting Ground Points from Airborne Lidar Point Clouds
摘要： Airborne light detection and ranging (lidar) has become a powerful support for acquiring geospatial data in numerous geospatial applications and analyses. However, the process of extracting ground points accurately and effectively from raw point clouds remains a big challenge. This study presents an improved top-hat filter with a sloped brim to enhance the robustness of ground point extraction for complex objects and terrains. The top-hat transformation is executed and the elevation change intensity of the transitions between the obtained top-hats and outer brims is inspected to suppress the omission error caused by protruding terrain features. Finally, the nonground objects of complex structures, such as multilayer buildings, are identified by the brim filter that is extended outward. The performance of the proposed filter in various environments is evaluated using diverse datasets with difficult cases. The comparison of the proposed filter with the commercial software Terrasolid TerraScan and other popular filtering algorithms demonstrates the applicability and effectiveness of this filter. Experimental results show that the proposed filter has great promise in terms of its application in various types of landscapes. Abrupt terrain features with dramatic elevation changes are well preserved, and diverse objects with complicated shapes are effectively removed. This filter has minimal omission and commission error oscillation for different test areas and thus demonstrates a stable and reliable performance in diverse landscapes. In addition, the proposed algorithm has high computational efficiency because of its simple and efficient data structure and implementation.
关键词： point cloud,top-hat transformation,mathematical morphology,filtering,lidar
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE International Conference on Automation/XXIII Congress of the Chilean Association of Automatic Control (ICA-ACCA) - Concepcion, Chile (2018.10.17-2018.10.19)] 2018 IEEE International Conference on Automation/XXIII Congress of the Chilean Association of Automatic Control (ICA-ACCA) - Mobile LiDAR Scanner for the Generation of 3D Georeferenced Point Clouds
摘要： Mobile laser scanning systems are a modern tool used by leading companies in surveying. These systems are capable of making a three-dimensional reconstruction of the environment by capturing thousands of aligned points. This article describes a hardware and software-based solution for a 3D LiDAR scanner capable of generating a georeferenced point cloud. This solution uses an integrated microcomputer-based hardware architecture, integration of navigation components and data logging. In addition, the effect caused by the measurement errors of the inertial sensors is displayed. To minimize these undesired effects, the use of high-precision navigation system is necessary. For the estimation of the position and orientation of the data captured by the LiDAR sensor, a non-linear interpolation is used for the oversampling of navigation data. Likewise, the scientific problem of direct georeferencing is modeled with a mathematical approach to conventional robotic structure. The product developed meets the technical requirements for most applications in topographic surveys and structural modeling. The system is portable on multiple platforms such as land vehicles and unmanned aerial vehicles.
关键词： point cloud,LiDAR,georeferencing,INS,MLS,hardware
更新于2025-09-23 15:22:29
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Evaluation of cloud base height measurements from Ceilometer CL31 and MODIS satellite over Ahmedabad, India
摘要： Clouds play a tangible role in the Earth’s atmosphere and in particular, the cloud base height (CBH), which is linked to cloud type, is one of the most important characteristics to describe the influence of clouds on the environment. In the present study, CBH observations from Ceilometer CL31 were extensively studied during May 2013 to January 2015 over Ahmedabad (23.03? N, 72.54? E), India. A detailed comparison has been performed with the use of ground-based CBH measurements from Ceilometer CL31 and CBH retrieved from MODIS (Moderate Resolution Imaging Spectroradiometer) onboard Aqua and Terra satellite. CBH retrieved from MODIS is ～ 1.955 and ～ 1.093 km on 25 July 2014 and 1 January 2015 respectively, which matches well with ceilometer-measured CBH (～ 1.92 and ～ 1.097 km). Some interesting features of cloud dynamics viz. strong downdraft and updraft have been observed over Ahmedabad which revealed different cloud characteristics during monsoon and post-monsoon periods. CBH shows seasonal variation during the Indian summer monsoon and post-monsoon period. Results indicate that the ceilometer is an excellent instrument to precisely detect low- and mid-level clouds, and the MODIS satellite provides accurate retrieval of high-level clouds over this region. The CBH algorithm used for the MODIS satellite is also able to capture the low-level clouds.
关键词： monsoon,satellite,MODIS,post-monsoon,cloud dynamics,cloud base height,ceilometer
更新于2025-09-23 15:21:21
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New Optical Properties of Ice Crystals for Multi-Class Cloud Microphysics
摘要： New optical properties of ice crystals were implemented in a general circulation model (GCM). Ebert and Curry’s (1992) and Fu’s (1996) parametrizations are widely used in the GCM radiation scheme. However, the validity of the data is limited to an effective radius (size) of 130 or 140 μm. This limit exceeds the median of the effective radius of snow (~200 μm), which is computed from the multi-class cloud microphysics scheme. A comparable amount of snow exists in the upper atmosphere near the lower part of ice clouds. Although the cross section of snow (extinction probability) is smaller than cloud ice, its impact on radiation has not been properly considered so far. We constructed a new lookup table of optical properties based on recent data for an extended effective radius up to 500 μm. The old data (< 130 μm) also need to be updated with a more recent and elaborate method. We processed extensive data provided by Yang et al. (2013) and linked to the radiation module of the Korean Integrated Model (KIM). The new optical properties change the shortwave scattering features, thus increasing the heating rate. This tendency is checked in both one-dimensional and global weather forecast simulations. With the new optical properties, KIM shows better performance by reducing bias with respect to the Integrated Forecasting Systems (IFS) analysis data.
关键词： weather forecasting,optical properties,cloud microphysics,ice crystals,radiation scheme
更新于2025-09-23 15:21:21
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Real-Time Geometric Parameter Measurement of High-Speed Railway Fastener Based on Point Cloud from Structured Light Sensors
摘要： With the increase in the number of service years for high-speed railways, the foundation of the rail track suffers from settlement, which causes rail track irregularity. To adjust the position of the track and meet track regularity demands, several components of the fastening system will be replaced by different sized components. It is important to measure the exact geometric parameters for the components of a fastening system before adjusting the track. Currently, the measurement process is conducted manually, which is laborious and error-prone. In this paper, a real-time geometric parameter measurement system for high-speed railway fastener based on 2-D laser profilers is presented. Dense and precise 3-D point clouds of high-speed railway fasteners are obtained from the system. A fastener extraction method is presented to extract fastener point cloud and a region-growing algorithm is used to locate key components of the fastener. Then, the geometric parameter of the fastener is worked out. An experiment was conducted on a high-speed railway near Wuhan, China to verify the accuracy and repeatability of the system. The maximum root-mean-square-error between the manual measurement and the system measurement is 0.3 mm, which demonstrates adequate accuracy. This system can replace manual measurements and greatly improve the efficiency of geometric parameter measurements for fasteners.
关键词： fastener geometric parameter measurement,region grow,high-speed railway,dense point cloud,structured light sensor
更新于2025-09-23 15:21:21
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Cloud Detection of Optical Remote Sensing Image Time Series Using P-norm based Regression Model
摘要： An automatic multi-temporal method is proposed in this paper for cloud detection without known the reference image in prior. A series of reference images are provided by fitting robustly of the pixels of multi-temporal images contaminated by clouds to show the inherent gradual change of the landscape with time instants. Then the cloud is detected by thresholding the difference between the target and the reference images, which is found to be merely composed of the regression model error modeled as Gaussian noise and outliers corresponding to cloud and its shadow. The proposed method is compared with state-of-the-art algorithms on the LANDSAT dataset, and shows a better discrimination of cloud and cloud shadow covered pixels from the uncontaminated ones.
关键词： P-norm distribution,Robust regression,Robust scale estimation,Cloud detection,Multi-temporal
更新于2025-09-23 15:21:21
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Geospatial Big Data Processing in Hybrid Cloud Environments
摘要： The importance of big geospatial data hosted on cloud environments is constantly growing. Main reasons are the rapid increase in volume of remote sensing data, the trend to persistently store and share more in-situ data at higher sampling rates, and the reduced management overhead of data hosted on commercial cloud platforms compared to in-house solutions. At the same time, cloud computing has the advantage of high scalability (and often reliability) and the capability to match the increasing computational requirements entailed by Big Data processing. This paper discusses interoperability and portability issues of cloud computing architectures and introduces a standards-based architecture to facilitate geospatial big data processing in hybrid cloud environments by leveraging and extending standards released by the Open Geospatial Consortium, OGC.
关键词： Big Data,Standards,Geospatial,Cloud
更新于2025-09-23 15:21:21
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Cloud Detection from RGB Color Remote Sensing Images with Deep Pyramid Networks
摘要： Cloud detection from remotely observed data is a critical pre-processing step for various remote sensing applications. In particular, this problem becomes even harder for RGB color images, since there is no distinct spectral pattern for clouds, which is directly separable from the Earth surface. In this paper, we adapt a deep pyramid network (DPN) to tackle this problem. For this purpose, the network is enhanced with a pre-trained parameter model at the encoder layer. Moreover, the method is able to obtain accurate pixel-level segmentation and classification results from a set of noisy labeled RGB color images. In order to demonstrate the superiority of the method, we collect and label data with the corresponding cloud/non-cloudy masks acquired from low-orbit Gokturk-2 and RASAT satellites. The experimental results validates that the proposed method outperforms several baselines even for hard cases (e.g. snowy mountains) that are perceptually difficult to distinguish by human eyes.
关键词： Cloud Detection,Deep Pyramid Networks
更新于2025-09-23 15:21:21
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Reconstruction and analysis of erythemal UV radiation time series from Hradec Králové (Czech Republic) over the past 50 years
摘要： This paper evaluates the variability of erythemal ultraviolet (EUV) radiation from Hradec Králové (Czech Republic) in the period 1964–2013. The EUV radiation time series was reconstructed using a radiative transfer model and 10 additional empirical relationships with the root mean square error of 9.9 %. The reconstructed time series documented the increase in EUV radiation doses in the 1980s and the 1990s (up to 15 % per decade), which is linked to the steep decline in total ozone (10 % per decade). The changes of cloud cover were the major factor affecting the EUV radiation doses especially in the 1960s, 1970s, and at the beginning of the new millennium. The mean annual EUV radiation doses in the decade 2004–2013 declined by 5 %. The factors affecting the EUV radiation doses differed also according to the chosen integration period (daily, monthly, and annually): solar zenith angle was the most important for daily doses, cloud cover for their monthly means, and the annual means of EUV radiation doses were most influenced by total ozone column. The number of days with very high EUV radiation doses increased by 22 % per decade, the increase was statistically significant in all seasons except autumn. The occurrence of the days with very high EUV doses was influenced mostly by low total ozone column (82 % of days), clear-sky or partly cloudy conditions (74 % of days) and by increased surface albedo (19 % of days). The principal component analysis documented that the occurrence of days with very high EUV radiation doses was much affected by the positive phase of North Atlantic Oscillation with an Azores High promontory reaching over central Europe. In the stratosphere, a strong Arctic circumpolar vortex and also the meridional inflow of ozone-poor air from the south-west were favourable for the occurrence of days with very high EUV radiation doses. This is the first analysis of the relationship between the high EUV radiation doses and macro-scale circulation patterns, and therefore more attention should be given also to other dynamical variables that may affect the solar UV radiation on the Earth surface.
关键词： cloud cover,erythemal ultraviolet radiation,atmospheric circulation patterns,total ozone column,surface albedo
更新于2025-09-23 15:21:21
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A novel approach for the extraction of cloud motion vectors using airglow imager measurements
摘要： The paper explores the possibility of implementing an advanced photogrammetric technique, generally employed for satellite measurements, on airglow imager, a ground-based remote sensing instrument primarily used for upper atmospheric studies, measurements of clouds for the extraction of cloud motion vectors (CMVs). The major steps involved in the algorithm remain the same, including image processing for better visualization of target elements and noise removal, identification of target cloud, setting a proper search window for target cloud tracking, estimation of cloud height, and employing 2-D cross-correlation to estimate the CMVs. Nevertheless, the implementation strategy at each step differs from that of satellite, mainly to suit airglow imager measurements. For instance, climatology of horizontal winds at the measured site has been used to fix the search window for target cloud tracking. The cloud height is estimated very accurately, as required by the algorithm, using simultaneous collocated lidar measurements. High-resolution, both in space and time (4 min), cloud imageries are employed to minimize the errors in retrieved CMVs. The derived winds are evaluated against MST radar-derived winds by considering it as a reference. A very good correspondence is seen between these two wind measurements, both showing similar wind variation. The agreement is also found to be good in both the zonal and meridional wind velocities with RMSEs < 2.4 m s?1. Finally, the strengths and limitations of the algorithm are discussed, with possible solutions, wherever required.
关键词： lidar measurements,photogrammetric technique,MST radar,cloud motion vectors,ground-based remote sensing,airglow imager
更新于2025-09-23 15:21:21