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Assessment of Slope-Adaptive Metrics of GEDI Waveforms for Estimations of Forest Aboveground Biomass over Mountainous Areas

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Journal of Remote Sensing 2021年第1期2021卷 180-196页

作者： wenjian ni Zhiyu Zhang Guoqing Sun State Key Laboratory of Remote Sensing Science Aerospace Information Research InstituteChinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China Department of Geographical Sciences University of MarylandCollege ParkMD 20742USA

Waveform broadening effects of large-footprint lidar caused by terrain slopes are still a great challenge limiting the estimation accuracy of forest aboveground biomass(AGB)over mountainous ***-adaptive metrics of waveforms were proposed in our previous ***,its validation was limited by the unavailability of enough reference *** study made full validation of slope-adaptive metrics using data acquired by the Global Ecosystem Dynamics Investigation(GEDI)mission,meanwhile exploring GEDI waveforms on estimations of forest *** types of waveform metrics were employed,including slope-adaptive metrics(RHT),typical height metrics relative to ground peaks(RH),and waveform parameters(WP).In addition to terrain slopes,two other factors were also explored including the geolocation issue and signal start and ending points of *** showed that footprint geolocations in the first version GEDI data products were shifted to the left forward of nominal geolocations with a distance of about 24 m~30 m and were substantially corrected in the second version;the fourth and fifth groups of signal start and ending points of waveforms had worse performance than the rest of the four groups because they used the maximum and minimum signal thresholds,*** airborne laser scanner(ALS)data as reference,the root mean square error(RMSE)of terrain slopes extracted from the digital elevation model of the shuttle radar topography mission(SRTM DEM)was about 3°.The coefficients of determination(R^(2))of estimation models of forest AGB based on RH metrics were improved from 0.48 to 0.68 with RMSE decreased from 19.7 Mg/ha to 15.4 Mg/ha by the second version *** RHT and WP metrics gave the best and the worst estimation accuracy,*** further improved R^(2) to 0.77 and decreased RMSE to 13.0 Mg/ha using terrain slopes extracted from SRTM DEM with a resolution of 1 arc second.R^(2) of estimation models based on RHT was finally

关键词： terrain estimation ground

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Characterization of ASTER GDEM elevation data over vegetated area compared with lidar data

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International Journal of Digital Earth 2015年第3期8卷 198-211页

作者： wenjian ni Guoqing Sun Kenneth J.Ranson State Key Laboratory of Remote Sensing Science Institute of Remote Sensing and Digital EarthChinese Academy of SciencesBeijingChina Department of Geographical sciences University of MarylandCollege ParkMDUSA Biospheric Sciences Branch NASA’s Goddard Space Flight CenterGreenbeltMDUSA

Current researches based on areal or spaceborne stereo images with very high resolutions(<1 m)have demonstrated that it is possible to derive vegetation height from stereo *** second version of the Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model(ASTER GDEM)is the state-of-the-art global elevation data-set developed by stereo ***,the resolution of ASTER stereo images(15 m)is much coarser than areal stereo images,and the ASTER GDEM is compiled products from stereo images acquired over 10 *** forest disturbances as well as forest growth are inevitable in 10 years time *** this study,the features of ASTER GDEM over vegetated areas under both flat and mountainous conditions were investigated by comparisons with lidar *** factors possibly affecting the extraction of vegetation canopy height considered include(1)co-registration of DEMs;(2)spatial resolution of digital elevation models(DEMs);(3)spatial vegetation structure;and(4)terrain *** results show that the accurate coregistration between ASTER GDEM and national elevation dataset(NED)is necessary over mountainous *** correlation between ASTER GDEM minus NED and vegetation canopy height is improved from 0.328 to 0.43 by degrading resolutions from 1 arc-second to 5 arc-second and further improved to 0.6 if only homogenous vegetated areas were considered.

关键词： vegetation canopy height ASTER GDEM NED photogrammetry stereo-mapping

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Regional Sampling of Forest Canopy Covers Using UAV Visible Stereoscopic Imagery for Assessment of Satellite-Based Products in Northeast China

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Journal of Remote Sensing 2022年第1期2022卷 311-324页

作者： Tianyu Yu wenjian ni Zhiyu Zhang Qinhuo Liu Guoqing Sun State Key Laboratory of Remote Sensing Science Aerospace Information Research InstituteChinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China Department of Geographical Sciences University of MarylandCollege ParkMD 20742USA

Canopy cover is an important parameter affecting forest succession,carbon fluxes,and wildlife *** global maps with different spatial resolutions have been produced based on satellite images,but facing the deficiency of reliable references for accuracy *** rapid development of unmanned aerial vehicle(UAV)equipped with consumer-grade camera enables the acquisition of high-resolution images at low cost,which provides the research community a promising tool to collect reference ***,it is still a challenge to distinguish tree crowns and understory green vegetation based on the UAV-based true color images(RGB)due to the limited spectral *** addition,the canopy height model(CHM)derived from photogrammetric point clouds has also been used to identify tree crowns but limited by the unavailability of understory terrain *** study proposed a simple method to distinguish tree crowns and understories based on UAV visible images,which was referred to as BAMOS for *** central idea of the BAMOS was the synergy of spectral information from digital orthophoto map(DOM)and structural information from digital surface model(DSM).Samples of canopy covers were produced by applying the BAMOS method on the UAV images collected at 77 sites with a size of about 1.0 km^(2) across Daxing’anling forested area in northeast of *** showed that canopy cover extracted by the BAMOS method was highly correlated to visually interpreted ones with correlation coefficient(r)of 0.96 and root mean square error(RMSE)of 5.7%.Then,the UAV-based canopy covers served as references for assessment of satellite-based maps,including MOD44B Version 6 Vegetation Continuous Fields(MODIS VCF),maps developed by the Global Land Cover Facility(GLCF)and by the Global Land Analysis and Discovery laboratory(GLAD).Results showed that both GLAD and GLCF canopy covers could capture the dominant spatial patterns,but GLAD canopy cover tended to miss scatte

关键词： maps Northeast Forest

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Forest height mapping using inventory and multi-source satellite data over Hunan Province in southern China

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Forest Ecosystems 2022年第1期9卷 57-70页

作者： Wenli Huang Wankun Min Jiaqi Ding Yingchun Liu Yang Hu wenjian ni Huanfeng Shen School of Resource and Environmental Sciences Wuhan UniversityHubei430079China State Key Laboratory of Remote Sensing Science Institute of Remote Sensing and Digital EarthChinese Academy of SciencesBeijing100101China College of Urban and Environmental Sciences Peking UniversityBeijing100871China Academy of Inventory and Planning National Forestry and Grassland AdministrationBeijing100714China School of Ecology and Environment Ningxia UniversityYinchuan750021China Breeding Base for State Key Laboratory of Land Degradation and Ecological Restoration in Northwest China Ningxia UniversityYinchuan750021China Key Laboratory for Restoration and Reconstruction of Degraded Ecosystem in Northwest China of Ministry of Education Ningxia UniversityYinchuan750021China

Background:Accurate mapping of forest canopy heights at a fine spatial resolution over large geographical areas is *** is essential for the estimation of forest aboveground biomass and the evaluation of forest *** current regional to national scale forest height maps were mainly produced at *** maps lack spatial details for decision-making at local *** advances in remote sensing provide great opportunities to fill this ***:In this study,we evaluated the utility of multi-source satellite data for mapping forest heights over Hunan Province in China.A total of 523 plot data collected from 2017 to 2018 were utilized for calibration and validation of forest height ***,the relationships between three types of in-situ measured tree heights(maximum-,averaged-,and basal area-weighted-tree heights)and plot-level remote sensing metrics(multispectral,radar,and topo variables from Landsat,Sentinel-1/PALSAR-2,and SRTM)were *** types of models(multilinear regression,random forest,and support vector regression)were *** variables were selected by two types of variable selection approaches(stepwise regression and random forest).Model parameters and model performances for different models were tuned and evaluated via a 10-fold cross-validation ***,tuned models were applied to generate wall-to-wall forest height maps for Hunan ***:The best estimation of plot-level tree heights(R2 ranged from 0.47 to 0.52,RMSE ranged from 3.8 to 5.3 m,and rRMSE ranged from 28%to 31%)was achieved using the random forest model.A comparison with existing forest height maps showed similar estimates of mean height,however,the ranges varied under different definitions of forest and types of tree ***:Primary results indicate that there are small biases in estimated heights at the province *** study provides a framework toward establishing regional to national scale maps of

关键词： Forest canopy height Hunan province Landsat ARD PALSAR-2 Sentinel-1

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Deforestation in Latin America in the 2000s predominantly occurred outside of typical mature forests

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The Innovation 2024年第3期5卷 88-98页

作者： Zhiyu Zhang wenjian ni Shaun Quegan Jingming Chen Peng Gong Luiz Carlos Estraviz Rodriguez Huadong Guo Jiancheng Shi Liangyun Liu Zengyuan Li Yating He Qinhuo Liu Yosio Shimabukuro Guoqing Sun Key Laboratory of Remote Sensing and Digital Earth Chinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Shijingshan DistrictBeijing 100049China Chinal of Mathematics and Statistics University of SheffieldSheffield S37RHUK Department of Geography and Program in Planning University of TorontoTorontoON M5S 3G3Canada Department of Earth Sciences and Department of Geography University of Hong KongHong KongChina Forest Science Department Luiz de Queiroz College of AgricultureUniversity of São PauloAv.Pádua Dias11Piracicaba 13418-900Brazil National Space Science Center Chinese Academy of SciencesBeijing 100190China Institute of Forest Resource Information Techniques Chinese Academy of ForestryBeijing 100091China Research Institute of Forest Policy and Information Chinese Academy of ForestryBeijing 100091China Remote Sensing Department National Institute for Space Research(INPE)Av.dos Astronautas 1758São Josédos Campos 12227-010Brazil Department of Geographical Sciences University of MarylandCollege ParkMD 20742USA

The role of tropical forests in the global carbon budget remains controversial,as carbon emissions from deforestation are highly *** high uncertainty arises from the use of either fixed forest carbon stock density or maps generated from satellite-based optical reflectance with limited sensitivity to biomass to generate accurate estimates of emissions from *** space missions aiming to accurately map the carbon stock density rely on direct measurements of the spatial structures of forests using lidar and *** found that lost forests are special cases,and their spatial structures can be directly measured by combining archived data acquired before and after deforestation by space missions principally aimed at measuring ***,using biomass mapping,we obtained new estimates of carbon loss from deforestation ahead of forthcoming space ***,using a high-resolution map of forest loss and the synergy of radar and lidar to estimate the aboveground biomass density of forests,we found that deforestation in the 2000s in Latin America,one of the severely deforested regions,mainly occurred in forests with a significantly lower carbon stock density than typical mature forests.

关键词： forest Latin lidar

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文本、语境与社会史视野

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文学评论 2020年第5期 46-50页

作者：倪文尖华东师范大学中文系

文学是什么?这个本质论问题已经历史化了。卡勒说,文学是什么?这要看是谁问了这问题。面对一个5岁的孩子,回答可以很干脆,而文学专业人士之间,则说来话长。事实上,他忘了一点,这还要看是在哪儿、在何时提出这问题。比如30年前,在《一份... 详细信息

文学是什么?这个本质论问题已经历史化了。卡勒说,文学是什么?这要看是谁问了这问题。面对一个5岁的孩子,回答可以很干脆,而文学专业人士之间,则说来话长。事实上,他忘了一点,这还要看是在哪儿、在何时提出这问题。比如30年前,在《一份杂志和一个“社团”——重评五四文学传统》[1]中,王晓明如是说:“每当看见‘文学现象’这四个字,我头一个想到的就是‘文本’,那由具体的作品和评论著作共同构成的文本。这当然不错,文本正是文学现象中最为重要的部分。但是,它不是惟一的部分,在它身前身后,还围着一大群也佩戴‘文学’徽章的事物。它们有的面目清楚,轮廓鲜明,譬如出版机构、作家社团;有的却身无定形,飘飘忽忽,譬如读者反应、文学规范。它们从各个方面围住文学文本,向它施加各种各样的影响。在许多时候,这些影响是如此深入,你单是为了看清楚文本自身的意义,也不得不先花力气去辨识它们。”

关键词：文学规范文学现象五四文学传统读者反应王晓明文学文本无定形文本自身

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海子《面朝大海,春暖花开》新说——b站讲课整理稿之一

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现代中文学刊 2022年第3期 80-84页

作者：倪文尖华东师范大学中文系

海子的《面朝大海,春暖花开》入选语文教科书后,几乎成了国民诗篇,并基本形成了两种读法。一种读成诗人选择世俗幸福的宣言,一种读成诗人告别人世的诀别诗。本文在与解读史对话过程中,重新发现文本关键点,揭示海子如何经由拟想体味“你... 详细信息

海子的《面朝大海,春暖花开》入选语文教科书后,几乎成了国民诗篇,并基本形成了两种读法。一种读成诗人选择世俗幸福的宣言,一种读成诗人告别人世的诀别诗。本文在与解读史对话过程中,重新发现文本关键点,揭示海子如何经由拟想体味“你”们的幸福,而召唤出那不可被说服的自“我”,以致最终放弃“在尘世获得幸福”,从而破解作品如何在文本肌理之中,铭刻诗人在生命最后阶段的复杂、纠结而也很合自身逻辑的隐秘心史。本文保留了讲课稿大白话、对话感、启发性的特点,不失为学术在网络时代走向大众、授人以渔的一种尝试,也希望并不因此而降低其思想深度和方法论企图。

关键词：海子《面朝大海春暖花开》文本关键点文本肌理想象与移情证史

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怀念吴福辉老师

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现代中文学刊 2021年第2期 34-36页

作者：倪文尖华东师范大学中文系

那天,早上醒来,依习惯看手机。看到一个现当代文学研究的群里:子善老师报告诸位不幸的消息,吴福辉先生今晨在加拿大突然逝世,享年82岁。太突然了!怎么可能?心存一丝侥幸,赶紧去问。子善老师的回复却是证实了。不久,收到李楠兄微信:"倪老... 详细信息

那天,早上醒来,依习惯看手机。看到一个现当代文学研究的群里:子善老师报告诸位不幸的消息,吴福辉先生今晨在加拿大突然逝世,享年82岁。太突然了!怎么可能?心存一丝侥幸,赶紧去问。子善老师的回复却是证实了。不久,收到李楠兄微信:"倪老师,早上接到吴老师儿子信,‘今天早上我爸在家突然去世,医生诊断为心脏病发作。’前天还在跟吴老师微信聊天。仿佛晴天霹雳!难以置信!"唉,心里堵得慌。起床了,人也呆呆的。

关键词：微信心脏病发作现当代文学研究李楠吴福辉子善老师加拿大

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这样的年代,批评何为?——致黄平

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南方文坛 2011年第3期 11-14页

作者：倪文尖华东师范大学中文系

黄平兄：新年好!是时间过得快，也是我动作真够慢。一快一幔，一晃，三年。

关键词：《这样的年代,批评何为?--致黄平》书信倪文尖文学

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面向森林高度提取的光学多角度立体观测影像模拟

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遥感学报 2023年第4期27卷 1034-1044页

作者：姚远倪文俭张志玉中国科学院空天信息创新研究院遥感科学国家重点实验室北京100101 中国科学院大学资源与环境学院北京100049

森林冠层高度是森林生态系统植被碳储量的重要指示因子之一。已有研究表明光学多角度立体观测(即摄影测量)数据具备森林冠层高度提取的潜力,然而光学影像容易受到云、雨等天气因素的影响,区域高精度森林冠层高度制图必需依靠多星多时相... 详细信息

森林冠层高度是森林生态系统植被碳储量的重要指示因子之一。已有研究表明光学多角度立体观测(即摄影测量)数据具备森林冠层高度提取的潜力,然而光学影像容易受到云、雨等天气因素的影响,区域高精度森林冠层高度制图必需依靠多星多时相数据融合才能实现。现有星载摄影测量系统获取的影像分辨率和观测角度差异较大,系统研究影像分辨率和观测角度变化对多角度立体观测点云垂直分布的影响规律,是实现多星多时相数据融合的前提。森林光学多角度立体观测模型是开展该研究的有效理论工具,但现有“森林光学多角度立体观测模型(LandStereo)”仅具备沿轨前后视立体观测影像模拟能力,无法用于WorldView等侧视立体观测影像的模拟分析。因此,本文对LandStereo模型进行了改进,使模型具备林区任意指定观测角度的影像模拟能力,进而利用改进后的模型对正视、正侧视和斜侧视等典型观测角度影像进行了模拟,并对不同观测角度组合构成的立体像对森林高度的提取精度进行了分析。结果表明,改进后的模型能够用于刻画森林冠层多角度立体特征,观测角度的变化是利用立体像对提取森林冠层高度精度的重要影响因素。本文为系统研究林区任意角度组合的多角度立体观测点云随影像分辨率和观测角度的变化规律提供了理论工具。

关键词：森林高度多角度立体观测影像模拟 LandStereo POV-Ray 植被光学模型

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