- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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Towards high throughput assessment of canopy dynamics: The estimation of leaf area structure in Amazonian forests with multitemporal multi-sensor airborne lidar
摘要： Leaf area dynamics offer information about changes in forest biomass and canopy function critical to understanding the role of forests in the climate system and carbon cycle. Airborne small footprint lidar is a potential major source for the detection of variation in leaf area density (LAD), LAD vertical profiles, and total leaf area (leaf area index, LAI), from sites to regional scales. However, the sensitivities of lidar-based LAD and LAI estimation are not yet well known, particularly in dense forests, over landscape heterogeneity, sensor system, and survey differences, and through time. To address these questions, we compared 16 pairs of multitemporal airborne lidar surveys with four different laser sensors across six Amazon forest sites with resurvey intervals ranging from one to nine years. We tested whether the different laser sensors, and the pulse return density of laser sampling (variable between and within each survey) introduce systematic biases. Laser sensors created consistent biases that accounted for up to 18.20% of LAD differences between surveys, but biases could be corrected with a simple regression approach. Lidar pulse return density had little appreciable bias impact when above 20 returns per m2. After correction, repeated mean and site maximum LAI estimates became significantly correlated (R2 ~0.8), while LAD profiles revealed site differences. Heterogeneity and change in LAD structure were detectable at the ecologically relevant 1/4 ha forest neighborhood grid scale, as evidenced by the high correlation of profile variation between surveys, with the strength of correlation (R2 value) significantly decreasing with increasing survey interval (0.74 to 0.16 from one to nine years), consistent with accumulating effects of forest dynamics. Sensor-induced biases trended towards correlation with lidar footprint (beam width). The LAD estimation and bias correction approach developed in this study provides the standardization critical for heterogeneous lidar networks that offer high throughput functional ecological monitoring of climatically important forests like the Amazon.
关键词： Tropical forest monitoring,Forest dynamics,LAI,Lidar,Forest degradation,Leaf area estimation,Leaf area profiles
更新于2025-09-23 15:21:01
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Retrieval of aerosol profiles by Raman lidar with dynamic determination of the lidar equation reference height
摘要： A reference height that often needs to be assumed in aerosol retrieval from Raman lidar tends to cause high uncertainty in retrieving the vertical distribution of aerosol optical properties. Here, a novel method is proposed to determine the height-revolved reference height, which is then used to retrieve aerosols from Raman lidar. This method can automatically avoid the atmospheric layers with the presence of aerosols, clouds and low signal to noise ratio (SNR). Based on elastic (at 355 nm) and inelastic (at 387 nm) signals collected during the period from 5 December 2016 to 5 March 2017 by a ground-based Raman lidar in Beijing, China, the aerosol optical properties, such as extinction coefficient, backscattering coefficient and lidar ratio have been successfully retrieved. Results show that the averaged nighttime aerosol optic depth (AOD) from Raman lidar is in good agreement with early morning AOD retrieved from a collocated sunphotometer. The AOD exhibits a strong diurnal variation with a peak at 1500 Beijing time. On average, the nighttime AOD at 355nm is 0.32, whereas the daytime AOD is 0.72 over Beijing during the study period. The column averaged lidar ratio is 44 sr at 355 nm, roughly consistent with previous studies. Our findings shed light on the pathways towards improving the retrieval of vertical distribution of aerosols optical properties during nighttime.
关键词： backscattering coefficients,Raman lidar,AOD,reference height
更新于2025-09-23 15:21:01
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INFLUENCE OF FLIGHT CONFIGURATION USED FOR LiDAR DATA COLLECTION ON INDIVIDUAL TREES DATA EXTRACTION IN FOREST PLANTATIONS
摘要： In the last decades, several studies have been conducted aiming to the extraction of forest variables from LiDAR data. Although such studies have indicated great potential, the high cost associated with LiDAR data acquisition process inhibits the technology to become an operational technique for forestry applications. The cost of a LiDAR survey, as for any other data collection techniques, is composed of fixed and variable costs. The variable portion, which can be optimized, is dependent, among other factors, on the number of flight hours. The flight time is mainly dependent on the flight configuration used for the survey. The objective of this paper is to investigate the impact of using different operational parameters on different species of forest plantations, to provide inputs for an adequate cost-benefit analysis. The different configurations are evaluated in terms of the number of individual trees automatically detected, individual height and volume, using the forest inventory as the reference data. The experiments have shown that compatible results are obtained using different configurations with flight time varying by a factor of 3.5 to 10 times. Also, for a given point density, preference should be given to the configuration based on a lower flying height.
关键词： volume,remote sensing,forest mensuration,Airborne LiDAR,tree height,progressive densification,operational parameters
更新于2025-09-23 15:21:01
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Novel Combined Spectral Indices Derived from Hyperspectral and Laser-Induced Fluorescence LiDAR Spectra for Leaf Nitrogen Contents Estimation of Rice
摘要： Spectra of re?ectance (Sr) and ?uorescence (Sf) are signi?cant for crop monitoring and ecological environment research, and can be used to indicate the leaf nitrogen content (LNC) of crops indirectly. The aim of this work is to use the Sr-Sf features obtained with hyperspectral and laser-induced ?uorescence LiDAR (HSL, LIFL) systems to construct novel combined spectral indices (NCIH-F) for multi-year rice LNC estimation. The NCIH-F is in a form of FWs*Φ + GSIs*Φ, where Φ is the Sr-Sf features, and FWs and GSIs are the feature weights and global sensitive indices for each characteristic band. In this study, the characteristic bands were chosen in di?erent ways. Firstly, the Sr-Sf characteristics which can be the intensity or derivative variables of spectra in 685 and 740 nm, have been assigned as the Φ value in NCIH-F formula. Simultaneously, the photochemical re?ectance index (PRI) formed with 531 and 570 nm was modi?ed based on a variant spectral index, called PRIfraction, with the Sf intensity in 740 nm, and then compared its potential with NCIH-F on LNC estimation. During the above analysis, both NCIH-F and PRIfraction values were utilized to model rice LNC based on the arti?cial neural networks (ANNs) method. Subsequently, four prior bands were selected, respectively, with high FW and GSI values as the ANNs inputs for rice LNC estimation. Results show that FW- and GSI-based NCIH-F are closely related to rice LNC, and the performance of previous spectral indices used for LNC estimation can be greatly improved by multiplying their FWs and GSIs. Thus, it can be included that the FW- and GSI-based NCIH-F constitutes an e?cient and reliable constructed form combining HSL (Sr) and LIFL (Sf) data together for rice LNC estimation.
关键词： hyperspectral LiDAR,combined spectral index,leaf nitrogen content,laser-induced ?uorescence LiDAR
更新于2025-09-23 15:19:57
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In-Situ LED-Based Observation of Snow Surface and Depth Transects
摘要： As part of a new snowpack monitoring framework, this study evaluated the feasibility of using an LED LIDAR (Leddar) time of ?ight sensor for snowpack depth measurement. The Leddar sensor has two additional features over simple sonic ranging sensors: (i) the return signal is divided into 16 segments across a 48° ?eld of view, each recording individual distance-to-target (DTT) measurements; (ii) an index of re?ectance or intensity signal is recorded for each segment. These two features provide information describing snowpack morphology and surface condition. The accuracy of Leddar sensor DTT measurements for snow depth monitoring was found to be < 20 mm, which was better than the 50 mm quoted by the manufacturer, and the precision was < 5 mm. Leddar and independent sonic ranger snow depth measurement showed strong linear agreement (r2 = 0.98). There was also a strong linear relationship (r2 = 0.98) between Leddar and manual ?eld snow depth measurements. The intensity signal response was found to correlate with snow surface albedo and inversely with air temperature (r = 0.77 and ?0.77, respectively).
关键词： snowpack depth,LED LIDAR,intensity,LIDAR,Leddar,sonic ranging device
更新于2025-09-23 15:19:57
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[Developments in Earth Surface Processes] Remote Sensing of Geomorphology Volume 23 || Landslide analysis using laser scanners
摘要： The advent of light detection and ranging (LiDAR) (see Table 1 for acronyms) has revolutionized the study of landslides and geomorphology because it provides an extraordinarily fine resolution topography (Carter et al., 2001). Electronic components and computers at affordable prices have made this technique widely available since the beginning of the 21st century. The number of geoscientific publications is increasing at a nearly exponential rate since around 1990 demonstrating its impact on geosciences (Abellan et al., 2016).
关键词： LiDAR,landslides,geomorphology,topography,laser scanning
更新于2025-09-23 15:19:57
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1.6 Micron Fiber Laser Source for CH <sub/>4</sub> Gas Leak Detection
摘要： We report on the development of a new pulsed fiber laser source at 1645.5 nm, based on stimulated Raman amplification. This laser source is intended to be used in a future lidar system, dedicated to methane gas leak monitoring in the vicinity of industrial facilities. In this paper we discuss reasons for choosing the 1645.5 nm wavelength, and then we present the two-stage amplification architecture of our fiber laser source under development. Recent experimental results and perspectives are drawn.
关键词： Raman amplification,fiber laser,methane gas leak detection,lidar
更新于2025-09-23 15:19:57
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[IEEE ESSCIRC 2019 - IEEE 45th European Solid State Circuits Conference (ESSCIRC) - Cracow, Poland (2019.9.23-2019.9.26)] ESSCIRC 2019 - IEEE 45th European Solid State Circuits Conference (ESSCIRC) - A 19-GHz Pulsed-Coherent ToF Receiver With 40-??m Precision for Laser Ranging Systems
摘要： This letter presents a pulsed-coherent time-of-flight (ToF) receiver for a laser ranging system implemented in 28-nm CMOS process. The prototype is designed at 19-GHz carrier frequency with 6.8-ns pulsed modulation. A segmented coarse-fine ToF measurement is adopted to achieve high resolution and fast acquisition. The coarse ToF is recorded by detecting the pulse’s edge whereas the fine measurement is measured by coherent detection. The proposed post-edge detection with automatic gain control loop provides better suppression of walk error from 600 to 26 ps as compared to the rising-edge detection. Also, phase-invariant variable-gain amplifiers provide a low phase error of < ±1? across gain settings with 60-dB dynamic range. This letter can, based on the timing accuracy, achieve 40-μm precision with 1-MHz sampling rate.
关键词： Lidar,time-of-flight (ToF),pulsed coherent,phase-invariant amplifier,walk error
更新于2025-09-23 15:19:57
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Optimisation for large-scale photovoltaic arraysa?? placement based on Light Detection And Ranging data
摘要： The availability of high-resolution LiDAR (Light Detection And Ranging) geospatial data has increased immensely, providing new opportunities to solve challenges in the field of spatial energy planning. This paper presents a new method for large-scale placement of photovoltaic arrays over buildings’ rooftops in an optimal manner by using the global optimisation approach. The position, aspect and slope are the key geometrical parameters being optimised for each photovoltaic array. The predicted energy generation (i.e. photovoltaic potential) is simulated by using state-of-the-art hourly shadowing estimation from the surroundings, anisotropic diffuse, reflected, and direct irradiances that are based on a Typical Meteorological Year, and non-linear efficiency characteristics of a considered photovoltaic system configuration. The optimisation performs multiple simulation scenarios throughout an entire year for each photovoltaic array, in order to maximise its photovoltaic potential. The method was tested over three LiDAR datasets with different landscape topographies and urban densities. In comparison to the methods for photovoltaic arrays’ fixed optimal slope estimation, the proposed method is substantially more suitable for application in urban environments.
关键词： LiDAR data,Optimisation,Photovoltaic potential,Environmental simulation
更新于2025-09-23 15:19:57
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Laser ranging measurements of turbulent water surfaces
摘要： Laser ranging is a measurement method, applied in a wide range of applications. In this study, laser ranging is used to measure the height of turbulent water flows. Measurements were performed in three cross sections of a confluence where a tributary flow meets the main flow. Both flows exhibited high Reynolds and Froude numbers where the free-water surface profiles were turbulent, non-stationary and non-homogeneous. Measurements were taken using a commercial LIDAR and a high-speed camera. The high-speed camera was operated on the principle of laser triangulation, using only the illumination from the LIDAR laser beam. Since, no other state-of-the-art method for measuring instantaneous water surface profiles exists, LIDAR and triangulation methods could only be compared with each other. The results show good agreement between both methods for the average turbulent water profile and fair agreement for instantaneous profiles. Presented herein is an explanation of these results.
关键词： Non-stationary surface,Free surface,Turbulence,High-speed camera,LIDAR,Laser triangulation
更新于2025-09-23 15:19:57