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Quantification of the spatiotemporal dynamics of diurnal fog and low stratus occurrence in subtropical montane cloud forests using Himawari-8 imagery and topographic attributes 利用 Himawari-8 图像和地形属性量化亚热带山地云雾林中昼雾和低层气发生的时空动态变化
IF 7.6 Q1 REMOTE SENSING Pub Date : 2024-10-11 DOI: 10.1016/j.jag.2024.104212
Montane cloud forests (MCFs) feature frequent, wind-driven cloud bands (fog and low stratus [FLS]), providing crucial moisture to the ecosystems. Elevated temperatures may displace FLS, impacting MCFs significantly. To evaluate the consequences, quantifying FLS occurrences is vital. In this study, we employed “RANdom forest GEneRator” (Ranger), an advanced machine learning algorithm, to detect diurnal (07:00–17:00) FLS (dFLS) occurrence from 2018 to 2021 in MCFs in northeast Taiwan using 31 variables, including the visible and infrared bands of the Advanced Himawari Imager onboard Himawari-8, pixel solar azimuth and zenith angles, band differences, the Normalized Difference Vegetation Index (NDVI) and topographic attributes. We applied simple (lumping all data) and three-mode (sunrise/sunset, cloudy and clear sky) models to predict dFLS occurrence. We randomly selected 80 % of the data for model development and the rest for validation by referring to four ground dFLS observation stations across an elevation range of 1151–1811 m a.s.l with 53,358 diurnal time-lapse photographs. We found that it was possible to detect dFLS occurrence in MCFs using both simple and three-mode models regardless of the weather conditions (F1 ≥ 0.864, accuracy ≥ 0.905 and the Matthews correlation coefficient ≥ 0.786); the performance of the simple model was slightly better. The NDVI was more important than other variables in both models. This study demonstrates that Ranger may be able to detect dFLS in MCFs solely using a comprehensive array of satellite features insensitive to varying atmospheric conditions and terrain effects, permitting systematic monitoring of dFLS over vast regions.
山地云雾林(MCFs)的特点是经常出现由风驱动的云带(雾和低层云 [FLS]),为生态系统提供重要的水分。气温升高可能会驱散雾和低层云,从而对山地云雾林造成严重影响。要评估其后果,量化雾和低层云的出现至关重要。在本研究中,我们采用先进的机器学习算法 "RANdom forest GEneRator"(Ranger),利用 31 个变量,包括 "向日葵-8 "号上的 "先进向日葵成像仪 "的可见光和红外波段、像素太阳方位角和天顶角、波段差异、归一化植被指数(NDVI)和地形属性,来检测 2018 年至 2021 年台湾东北部 MCF 的昼夜(07:00-17:00)FLS(dFLS)发生情况。我们采用简单模型(将所有数据合并)和三模式模型(日出/日落、阴天和晴天)来预测 dFLS 的发生。我们随机选取了 80% 的数据用于模型开发,其余数据用于验证,参考了海拔 1151-1811 米范围内的四个地面 dFLS 观测站,以及 53,358 张昼夜延时照片。我们发现,无论天气条件如何,使用简单模式和三模式模型都能检测到 MCF 中出现的 dFLS(F1 ≥ 0.864,准确度≥ 0.905,马修斯相关系数≥ 0.786);简单模式的性能稍好。在两个模型中,NDVI 都比其他变量更重要。这项研究表明,护林员可以仅利用对不同大气条件和地形影响不敏感的综合卫星特征阵列来检测微卷叶螟,从而对广大地区的微卷叶螟进行系统监测。
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引用次数: 0
Immediate assessment of forest fire using a novel vegetation index and machine learning based on multi-platform, high temporal resolution remote sensing images 利用基于多平台、高时间分辨率遥感图像的新型植被指数和机器学习对森林火灾进行即时评估
IF 7.6 Q1 REMOTE SENSING Pub Date : 2024-10-11 DOI: 10.1016/j.jag.2024.104210
Forest fires pose a significant threat to ecosystems, biodiversity, and human settlements, necessitating accurate and timely detection of burned areas for post-fire management. This study focused on the immediate assessment of a recent major forest fire that occurred on March 15, 2024, in southwestern China. We comprehensively utilized high temporal resolution MODIS and Black Marble nighttime light images to monitor the fire’s development and introduced a novel method for detecting burned forest areas using a new Shadow-Enhanced Vegetation Index (SEVI) coupling with a machine learning technique. The SEVI effectively enhances the vegetation index (VI) values on shaded slopes and hence reduces the VI disparity between shaded and sunlit areas, which is critical for accurately extracting fire scars in such terrain. While SEVI primarily identifies burned forest areas, the Random Forest (RF) technique detects all burned areas, including both forested and non-forested regions. Consequently, the total burned area of the Yajiang forest fire was estimated at 23,588 ha, with the burned forest area covering 19,266 ha. The combination of SEVI and RF algorithms provided a comprehensive and efficient tool for identifying burned areas. Additionally, our study employed the Remote Sensing-based Ecological Index (RSEI) to assess the ecological impact of the fire on the region, uncovering an immediate 15 % decline in regional ecological conditions following the fire. The usage of RSEI has the potential to quantitatively understand ecological responses to the fire. The findings achieved in this study underscore the significance of precise fire-burned area extraction techniques for enhancing forest fire management and ecosystem recovery strategies, while also highlighting the broader ecological implications of such events.
森林火灾对生态系统、生物多样性和人类居住区构成重大威胁,因此需要准确及时地探测火灾区域,以便进行火后管理。本研究的重点是对 2024 年 3 月 15 日发生在中国西南部的一场重大森林火灾进行即时评估。我们综合利用了高时间分辨率的 MODIS 和黑云母夜间光照图像来监测火灾的发展,并引入了一种新的方法,即利用新的阴影增强植被指数(SEVI)与机器学习技术相结合来检测烧毁林区。SEVI 可有效增强阴影斜坡上的植被指数(VI)值,从而缩小阴影和阳光照射区域之间的植被指数差异,这对于在此类地形中准确提取火烧痕至关重要。SEVI 主要识别烧毁的森林区域,而随机森林(RF)技术则检测所有烧毁区域,包括森林和非森林区域。因此,雅江森林火灾的总烧毁面积估计为 23,588 公顷,其中烧毁森林面积为 19,266 公顷。SEVI 算法和射频算法的结合为识别烧毁区域提供了一个全面、高效的工具。此外,我们的研究还采用了基于遥感的生态指数(RSEI)来评估火灾对该地区的生态影响,发现火灾发生后,该地区的生态条件立即下降了 15%。使用 RSEI 有可能从数量上了解火灾对生态的影响。本研究的发现强调了精确的火灾燃烧区提取技术对加强森林火灾管理和生态系统恢复战略的重要意义,同时也突出了此类事件对生态的广泛影响。
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引用次数: 0
Development of a coral and competitive alga-related index using historical multi-spectral satellite imagery to assess ecological status of coral reefs 利用历史多光谱卫星图像开发珊瑚和竞争性藻类相关指数,以评估珊瑚礁的生态状况
IF 7.6 Q1 REMOTE SENSING Pub Date : 2024-10-11 DOI: 10.1016/j.jag.2024.104194
Understanding the characteristics of the growth zones of live corals and competitive algae, including turf algae and macroalgae, is crucial for assessing the degradation of coral reef ecosystems. However, identifying live corals and competitive algae in multispectral satellite images is challenging because different objects can have similar spectra. To address this, we used two satellite images acquired at different times (Landsat thematic mapper (TM), Landsat operational land imager (OLI), or Sentinel-2 multi-spectral instrument (MSI)) to assess the growth zone characteristics of live corals and competitive algae. This assessment leveraged the seasonal dieback of competitive algae and the relative stability of live-coral growth zones over a short period. Specifically, we developed a normalized red–green difference index (NRGI) to segment live-coral-or-competitive-alga growth zones in satellite images. By comparing the segmentation results from an image captured during a period with few competitive algae and another image captured during a period with lush competitive algae, we estimated the growth zone areas of the live corals and competitive algae. Finally, we calculated the ratio of the competitive-alga growth zone area to the live-coral growth zone area (RCL). Experiments on eight typical coral islands and reefs in the South China Sea (SCS) from 1995 to 2022 revealed that: (1) the identification accuracies of live-coral-or-competitive-alga growth zones reached 80.3 % and 92.6 % during periods with few competitive algae (January to March) and lush competitive algae (April to October), respectively; (2) the RCL was well correlated with the coral-macroalgae encounter rate (an ecological index indicating the pressure of the competitive algae on the live corals) (r = 0.79, P<0.05); and (3) the trends in the growth zones of competitive algae and live corals, along with the RCL, were consistent with major ecological events in the SCS, such as coral bleaching, outbreak of Acanthaster planci, and black band disease. (4) Moreover, a time-lagged correlation was observed between heat stress and the RCL. In summary, the proposed approach is simple, effective, and feasible. The RCL is a valuable indicator of the status of coral reef ecosystems, highlighting the pressure of competitive algae on live corals and the degradation of coral reef ecosystems. This method introduces a novel application of multispectral satellite images for assessing coral reef ecosystems and has significant potential for future coral reef ecosystem monitoring.
了解活珊瑚和竞争性藻类(包括草皮藻和大型藻类)生长区的特征对于评估珊瑚礁生态系统的退化情况至关重要。然而,在多光谱卫星图像中识别活珊瑚和竞争性藻类具有挑战性,因为不同的物体可能具有相似的光谱。为了解决这个问题,我们使用了在不同时间获取的两幅卫星图像(大地遥感卫星专题成像仪(TM)、大地遥感卫星业务陆地成像仪(OLI)或哨兵-2 多光谱仪器(MSI))来评估活珊瑚和竞争性藻类的生长区特征。该评估利用了竞争性藻类的季节性枯死和活珊瑚生长区在短时间内的相对稳定性。具体来说,我们开发了一种归一化红-绿差异指数(NRGI)来分割卫星图像中的活珊瑚或竞争藻类生长区。通过比较一张竞争藻类较少时期拍摄的图像和另一张竞争藻类茂盛时期拍摄的图像的分割结果,我们估算出了活珊瑚和竞争藻类的生长区面积。最后,我们计算了竞争藻生长区面积与活珊瑚生长区面积的比率(RCL)。1995 年至 2022 年在中国南海(SCS)8 个典型珊瑚岛和珊瑚礁上进行的实验表明(1) 在竞争藻较少的时期(1 月至 3 月)和竞争藻较多的时期(4 月至 10 月),活珊瑚生长区或竞争藻生长区的识别准确率分别达到 80.3% 和 92.6%;(2) RCL 与珊瑚-巨藻相遇率(表示竞争藻对活珊瑚压力的生态指数)具有良好的相关性(r = 0.79,P<0.05);(3)竞争藻类和活珊瑚的生长区以及 RCL 的变化趋势与南中国海的重大生态事件(如珊瑚白化、钝头栉水母爆发和黑带病)相一致。(4) 此外,还观察到热应力与 RCL 之间存在时滞相关性。总之,建议的方法简单、有效、可行。RCL 是反映珊瑚礁生态系统状况的一个重要指标,可突出显示竞争性藻类对活珊瑚的压力和珊瑚礁生态系统的退化。该方法引入了多光谱卫星图像在珊瑚礁生态系统评估中的新应用,在未来珊瑚礁生态系统监测中具有巨大潜力。
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引用次数: 0
Rice recognition from Sentinel-1 SLC SAR data based on progressive feature screening and fusion 基于渐进式特征筛选和融合的哨兵-1 SLC SAR 数据的水稻识别
IF 7.6 Q1 REMOTE SENSING Pub Date : 2024-10-07 DOI: 10.1016/j.jag.2024.104196
Rice, a crucial global food crop, necessitates accurate mapping for food security assessment. China, a major rice producer and consumer, includes Jiangsu Province as a significant rice production region. The Hongzehu (HZH) area in Jiangsu contributes substantially to rice supply, supporting food security locally and province-wide. Sentinel-1 SAR data, particularly Single Look Complex (SLC) products, holds promise for precise crop mapping with enhanced phase and polarization information, enhancing sensitivity to rice growth changes by analyzing rice surface features information. However, challenges persist, especially climate impacts and timing inconsistencies between fields for planting rice. To overcome this, our study proposes a progressive feature screening and fusion method using multi-temporal SAR images. We introduce fuzzy coarse screening based on statistical distribution characteristics and refine it with Gaussian fitting. A model incorporating time-series sample separation and polarization decomposition feature fusion based on rice growth height enhances rice growth expression. For more precise results, we advocate a multi-temporal feature fusion approach using optimized sample features in the BiLSTM network to characterize rice growth and ground features. Experimental results demonstrate the method’s efficacy in two cities with a limited number of sampling points. The progressive feature fusion (DF) method outperforms classical classification methods using single feature (SF) or combined features (CF). Our proposed strategy proves effective for rice mapping applications, providing a promising approach for leveraging Sentinel-1 SLC SAR data. In conclusion, our study enhances accuracy in identifying rice fields and characterizing rice growth, contributing to improved food security assessments despite challenges associated with rainy seasons and planting times.
水稻是全球重要的粮食作物,需要精确的测绘来进行粮食安全评估。中国是稻米生产和消费大国,江苏省是重要的稻米产区。江苏洪泽湖(HZH)地区对水稻供应做出了巨大贡献,为当地和全省的粮食安全提供了支持。哨兵-1合成孔径雷达数据,特别是单看复合(SLC)产品,通过分析水稻表面特征信息,增强了相位和偏振信息,有望精确绘制作物图,提高对水稻生长变化的敏感性。然而,挑战依然存在,特别是气候影响和不同田块的插秧时间不一致。为了克服这一问题,我们的研究提出了一种利用多时相合成孔径雷达图像的渐进式特征筛选和融合方法。我们引入了基于统计分布特征的模糊粗筛选,并通过高斯拟合对其进行细化。基于水稻生长高度的时间序列样本分离和偏振分解特征融合模型增强了水稻生长表达。为了获得更精确的结果,我们提倡在 BiLSTM 网络中使用优化样本特征的多时相特征融合方法,以表征水稻生长和地面特征。实验结果证明了该方法在两个采样点数量有限的城市中的有效性。渐进式特征融合(DF)方法优于使用单一特征(SF)或组合特征(CF)的经典分类方法。我们提出的策略在水稻测绘应用中证明是有效的,为利用 Sentinel-1 SLC SAR 数据提供了一种前景广阔的方法。总之,我们的研究提高了识别稻田和描述水稻生长特征的准确性,有助于改进粮食安全评估,尽管存在与雨季和种植时间相关的挑战。
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引用次数: 0
CSStereo: A UAV scenarios stereo matching network enhanced with contrastive learning and feature selection CSStereo:利用对比学习和特征选择增强的无人机场景立体匹配网络
IF 7.6 Q1 REMOTE SENSING Pub Date : 2024-10-07 DOI: 10.1016/j.jag.2024.104189
Stereo matching is essential for establishing pixel-level correspondences and estimating depth in scene reconstruction. However, applying stereo matching networks to UAV scenarios presents unique challenges due to varying altitudes, angles, and rapidly changing conditions, unlike the controlled settings in autonomous driving or the uniform scenes in satellite imagery. To address these UAV-specific challenges, we propose the CSStereo network (Contrastive Learning and Feature Selection Stereo Matching Network), which integrates contrastive learning and feature selection modules. The contrastive learning module enhances feature representation by comparing similarities and differences between samples, thereby improving discrimination among features in UAV scenarios. The feature selection module enhances robustness and generalization across different UAV scenarios by selecting relevant and informative features. Extensive experimental evaluations demonstrate the effectiveness of CSStereo in UAV scenarios, and show superior performance in both qualitative and quantitative assessments.
立体匹配对于在场景重建中建立像素级对应关系和估计深度至关重要。然而,与自动驾驶中的受控环境或卫星图像中的统一场景不同,由于高度、角度和条件瞬息万变,在无人机场景中应用立体匹配网络面临着独特的挑战。为了应对这些无人机特有的挑战,我们提出了 CSStereo 网络(对比学习和特征选择立体匹配网络),该网络集成了对比学习和特征选择模块。对比学习模块通过比较样本之间的相似性和差异性来增强特征表示,从而提高无人机场景中特征之间的辨别能力。特征选择模块通过选择相关和信息量大的特征来增强不同无人机场景下的鲁棒性和泛化能力。广泛的实验评估证明了 CSStereo 在无人机应用场景中的有效性,并在定性和定量评估中显示出卓越的性能。
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引用次数: 0
Fusion of multi-source wave spectra based on BU-NET 基于 BU-NET 的多源波谱融合
IF 7.6 Q1 REMOTE SENSING Pub Date : 2024-10-07 DOI: 10.1016/j.jag.2024.104195
The wave spectrum describes the distribution of wave energy across frequency and direction. Obtaining wave spectrum information with high accuracy is of great value for oceanographic research and disaster prevention and reduction. Currently, wave spectral data can be obtained from remote sensing observations, global meteorological and climate reanalysis products, and in-situ observations, which exhibit different advantages and limitations in terms of spatio-temporal resolution, accuracy, and data coverage. Fusing these diverse spectral data to complement the advantage of improving the accuracy of wave spectrum is very promising. However, there is still no simple and effective method to fuse the above spectral data. In this study, a multi-source spectral fusion method is developed based on BU-NET, which realizes the integration of ERA5 spectra and SWIM spectra, with buoy spectra as the reference. The results of the systematic evaluation indicate that the fusion spectra alleviate parasitic peaks, address the issue of larger mean energy, and compensate for energy loss due to the cutoff frequency in the SWIM spectra. The fusion spectra also alleviate energy underestimation during high sea states in the ERA5 spectra. Furthermore, the accuracy of the significant wave height, mean wave period, dominant wave period, and dominant wave direction obtained from the fusion spectra is improved. The root mean square errors between these parameters from the fusion spectra and those from buoy spectra are 0.217 m, 0.378 s, 1.599 s, and 33.094°, respectively.
波谱描述了波能在不同频率和方向上的分布。获取高精度的波谱信息对海洋学研究和防灾减灾具有重要价值。目前,波谱数据可以从遥感观测、全球气象和气候再分析产品以及现场观测中获得,这些数据在时空分辨率、精度和数据覆盖范围等方面表现出不同的优势和局限性。将这些不同的光谱数据融合在一起,优势互补,提高波谱的精度是非常有前景的。然而,目前仍没有简单有效的方法来融合上述光谱数据。本研究基于 BU-NET 开发了一种多源波谱融合方法,以浮标波谱为参考,实现了 ERA5 波谱与 SWIM 波谱的融合。系统评估结果表明,融合光谱可减轻寄生峰,解决平均能量较大的问题,并补偿 SWIM 光谱中截止频率造成的能量损失。融合频谱还减轻了ERA5频谱在高海况下对能量的低估。此外,从融合频谱获得的显著波高、平均波周期、主波周期和主波方向的精度也有所提高。融合频谱与浮标频谱得出的这些参数的均方根误差分别为 0.217 米、0.378 秒、1.599 秒和 33.094°。
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引用次数: 0
Exploring the effects of different combination ratios of multi-source remote sensing images on mangrove communities classification 探索多源遥感图像不同组合比例对红树林群落分类的影响
IF 7.6 Q1 REMOTE SENSING Pub Date : 2024-10-07 DOI: 10.1016/j.jag.2024.104197
Mangroves are one of the most important marine ecosystems globally, their spatial distribution is crucial for promoting mangrove ecosystems conservation, restoration, and sustainable managements. This study proposed a novel Unet-Multi-Scale High-Resolution Vision Transformer (UHRViT) model for classifying mangrove species using unmanned aerial vehicle (UAV-RGB), UAV-LiDAR, and Gaofen-3 Synthetic Aperture Radar (GF-3 SAR) images. The UHRViT utilized a multi-scale high-resolution visual Transformer as its backbone network and was designed to a multi-branch U-shaped network structure to extract features of different scales layer by layer, and to facilitate the interaction of high and low-level semantic information. We further verified the classification performance superiority of UHRViT model by comparing to HRViT and HRNetV2 algorithms. We also systematically investigated the effects of active–passive image combination ratios on mangrove communities mapping. The results revealed that: UAV-RGB images exhibited the better classification accuracy (mean F1-score>95 %) for mangrove species than UAV-LiDAR and GF-3 SAR images; The classification performances and stability of UHRViT algorithm in the fifteen datasets outperformed the HRViT and HRNetV2 algorithms; Combining UAV-RGB with GF-3 SAR or UAV-LiDAR images respectively, both achieved better classifications than the single data source. Based on the UHRViT algorithm, the combination of UAV-RGB and UAV-LiDAR achieved the highest classification accuracy (Iou = 0.944, MIou = 50.2 %) for Avicennia corniculatum (AC). When the combination ratio of UAV-RGB with GF-3 SAR or UAV-LiDAR was 3:1, Avicennia marina and AC both obtained the optimal classification accuracy with average F1-scores of 98.19 % and 97.3 %, respectively. Our works revealed that the changes in the classification accuracies of mangrove communities under multi-sensor image combination ratios, and demonstrated that our model could effectively improve the classification accuracy of mangrove communities.
红树林是全球最重要的海洋生态系统之一,其空间分布对促进红树林生态系统的保护、恢复和可持续管理至关重要。本研究提出了一种新颖的 Unet 多尺度高分辨率视觉变换器(UHRViT)模型,用于利用无人机(UAV-RGB)、无人机激光雷达(UAV-LiDAR)和高分三号合成孔径雷达(GF-3 SAR)图像对红树林物种进行分类。UHRViT 采用多尺度高分辨率视觉转换器作为骨干网络,并设计成多分支 U 型网络结构,以逐层提取不同尺度的特征,并促进高低级语义信息的交互。通过与 HRViT 和 HRNetV2 算法的比较,我们进一步验证了 UHRViT 模型的分类性能优势。我们还系统地研究了主动-被动图像组合比例对红树林群落绘图的影响。结果显示与 UAV-LiDAR 和 GF-3 SAR 图像相比,UAV-RGB 图像表现出更高的红树林物种分类准确率(平均 F1 分数>95%);UHRViT 算法在 15 个数据集中的分类性能和稳定性优于 HRViT 和 HRNetV2 算法;将 UAV-RGB 与 GF-3 SAR 或 UAV-LiDAR 图像分别结合使用,分类效果均优于单一数据源。根据 UHRViT 算法,UAV-RGB 与 UAV-LiDAR 的组合对 Avicennia corniculatum(AC)的分类准确率最高(Iou = 0.944,MIou = 50.2 %)。当 UAV-RGB 与 GF-3 SAR 或 UAV-LiDAR 的组合比例为 3:1 时,Avicennia marina 和 AC 都获得了最佳分类精度,平均 F1 分数分别为 98.19 % 和 97.3 %。我们的研究揭示了多传感器图像组合比例下红树林群落分类精度的变化,证明我们的模型能有效提高红树林群落的分类精度。
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引用次数: 0
Improving the accuracy of SIF quantified from moderate spectral resolution airborne hyperspectral imager using SCOPE: assessment with sub-nanometer imagery 利用 SCOPE 提高中等光谱分辨率机载高光谱成像仪量化 SIF 的精度:利用亚纳米图像进行评估
IF 7.6 Q1 REMOTE SENSING Pub Date : 2024-10-07 DOI: 10.1016/j.jag.2024.104198
Hyperspectral imaging of solar-induced chlorophyll fluorescence (SIF) is required for plant phenotyping and stress detection. However, the most accurate instruments for SIF quantification, such as sub-nanometer (≤1-nm full-width at half-maximum, FWHM) airborne hyperspectral imagers, are expensive and uncommon. Previous studies have demonstrated that standard narrow-band hyperspectral imagers (i.e., 4–6-nm FWHM) are more cost-effective and can provide far-red SIF quantified at 760 nm (SIF760), which correlates strongly with precise sub-nanometer resolution measurements. Nevertheless, narrow-band SIF760 quantifications are subject to systematic overestimation owing to the influence of the spectral resolution (SR). In this study, we propose a modelling approach based on the Soil Canopy Observation, Photochemistry and Energy Fluxes (SCOPE) model with the objective of enhancing the accuracy of absolute SIF760 levels derived from standard airborne hyperspectral imagers in practical settings. The performance of the proposed method was evaluated using airborne imagery acquired from two airborne hyperspectral imagers (FWHM ≤ 0.2-nm and 5.8-nm) flown in tandem on board an aircraft that collected data from two different wheat and maize phenotyping trials. Leaf biophysical and biochemical traits were first estimated from airborne narrow-band reflectance imagery and subsequently used as SCOPE model inputs to simulate a range of top-of-canopy (TOC) radiance and SIF spectra at 1-nm FWHM. The SCOPE simulated radiance spectra were then convolved to match the spectral configuration of the narrow-band imager to compute the 5.8-nm FWHM SIF760. A site-specific model was constructed by employing the convolved 5.8-nm SR SIF760 as the independent variable and the 1-nm SR SIF760 directly simulated by SCOPE as the dependent variable. When applied to the airborne dataset, the estimated SIF760 at 1-nm SR from the standard narrow-band hyperspectral imager matched the reference sub-nanometer quantified SIF760 with root mean square error (RMSE) less than 0.5 mW/m2/nm/sr, yielding R2 = 0.93–0.95 from the two experiments. These results suggest that the proposed modelling approach enables the interpretation of SIF760 quantified using standard hyperspectral imagers of 4–6 nm FWHM for stress detection and plant physiological condition assessment.
植物表型和胁迫检测需要太阳诱导叶绿素荧光(SIF)的高光谱成像。然而,用于 SIF 定量的最精确仪器,如亚纳米级(半最大值全宽≤1 纳米,FWHM)机载高光谱成像仪,既昂贵又不常见。以往的研究表明,标准窄带高光谱成像仪(即 4-6 纳米 FWHM)更具成本效益,可提供 760 纳米(SIF760)的远红外 SIF 量化值,这与精确的亚纳米分辨率测量结果密切相关。然而,由于光谱分辨率(SR)的影响,窄带 SIF760 定量可能会出现系统性高估。在本研究中,我们提出了一种基于土壤冠层观测、光化学和能量通量(SCOPE)模型的建模方法,目的是在实际环境中提高由标准机载高光谱成像仪得出的 SIF760 绝对值的准确性。我们使用两架机载高光谱成像仪(FWHM ≤ 0.2-nm 和 5.8-nm)获取的机载图像对所提方法的性能进行了评估,这两架机载高光谱成像仪在一架飞机上串联飞行,收集了来自两个不同的小麦和玉米表型试验的数据。首先通过机载窄带反射图像估算叶片的生物物理和生物化学特征,然后将其作为 SCOPE 模型的输入,以模拟一系列 1-nm FWHM 的冠顶 (TOC) 辐射和 SIF 光谱。然后对 SCOPE 模拟的辐射率光谱进行卷积,以匹配窄带成像仪的光谱配置,从而计算出 5.8-nm FWHM 的 SIF760。将卷积的 5.8-nm SR SIF760 作为自变量,将 SCOPE 直接模拟的 1-nm SR SIF760 作为因变量,构建了一个特定站点模型。当应用于机载数据集时,标准窄带高光谱成像仪估算的 1-nm SR SIF760 与参考的亚纳米量化 SIF760 相匹配,均方根误差 (RMSE) 小于 0.5 mW/m2/nm/sr,两次实验的 R2 = 0.93-0.95。这些结果表明,所提出的建模方法能够解释使用 4-6 nm FWHM 的标准高光谱成像仪量化的 SIF760,用于胁迫检测和植物生理状况评估。
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引用次数: 0
Can we detect plant diseases without prior knowledge of their existence? 我们能否在事先不知道植物病害存在的情况下检测到植物病害?
IF 7.6 Q1 REMOTE SENSING Pub Date : 2024-10-07 DOI: 10.1016/j.jag.2024.104192
There is a need to help farmers make decisions to maximize crop yields. Many studies have emerged in recent years using deep learning on remotely sensed images to detect plant diseases, which can be caused by multiple factors such as environmental conditions, genetics or pathogens. This problem can be considered as an anomaly detection task. However, these approaches are often limited by the availability of annotated data or prior knowledge of the existence of an anomaly. In many cases, it is not possible to obtain this information. In this work, we propose an approach that can detect plant anomalies without prior knowledge of their existence, thus overcoming these limitations. To this end, we train a model on an auxiliary prediction task using a dataset composed of samples of normal and abnormal plants. Our proposed method studies the distribution of heatmaps retrieved from an explainability model. Based on the assumptions that the model trained on the auxiliary task is able to extract important plant characteristics, we propose to study how closely the heatmap of a new observation follows the heatmap distribution of a normal dataset. Through the proposed a contrario approach, we derive a score indicating potential anomalies.
Experiments show that our approach outperforms reference approaches such as f-AnoGAN and OCSVM on the GrowliFlower and PlantDoc datasets and has competitive performances on the PlantVillage dataset, while not requiring the prior knowledge on the existence of anomalies.
有必要帮助农民做出决策,最大限度地提高作物产量。近年来出现了许多利用遥感图像深度学习检测植物病害的研究,植物病害可能由环境条件、遗传或病原体等多种因素引起。这一问题可视为异常检测任务。然而,这些方法往往受限于注释数据的可用性或异常现象存在的先验知识。在很多情况下,我们无法获得这些信息。在这项工作中,我们提出了一种无需事先了解植物异常现象的方法,从而克服了这些限制。为此,我们使用由正常和异常植物样本组成的数据集,在辅助预测任务中训练一个模型。我们提出的方法研究了从可解释性模型中检索到的热图分布。基于在辅助任务中训练的模型能够提取重要植物特征的假设,我们建议研究新观察结果的热图与正常数据集热图分布的密切程度。实验表明,我们的方法在 GrowliFlower 和 PlantDoc 数据集上的表现优于 f-AnoGAN 和 OCSVM 等参考方法,在 PlantVillage 数据集上的表现也很有竞争力,而且不需要事先了解异常情况的存在。
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引用次数: 0
Public responses to heatwaves in Chinese cities: A social media-based geospatial modelling approach 中国城市公众对热浪的反应:基于社交媒体的地理空间建模方法
IF 7.6 Q1 REMOTE SENSING Pub Date : 2024-10-06 DOI: 10.1016/j.jag.2024.104205
Increasing exposure to heatwaves threatens public health, challenging various socioeconomic sectors in the coming decades. Prior studies mostly concentrated on the heatwaves occurring in specific regions by examining temperature durations, ignoring the fact that heatwaves typically swept across a large area. To comprehensively assess the effects of heatwaves, we jointly analyzed public attention to heatwaves using a dataset of over 10 million geo-located Weibo tweets across 321 cities in China. By considering spatial disparities, two kinds of public attention at city level, namely the number of heat-related tweets (NHTs) and the ratio of heat-related tweets (RHTs), were designed to indicate the severity and location of heatwave impacts, respectively. The heat cumulative intensity was used as a proxy for heatwaves, which exhibited more significant correlations with RHTs than NHTs. The multiscale geographically weighted regression (MGWR) model was employed to investigate the spatiotemporal variations of environment, demographic, and economic-social factors. Six city groups were clustered with MGWR coefficients that were consistent with the seven geographic subregions of China. This research provides a new perspective and methodology for public attention to heatwaves using geo-located social sensing data and highlights the need for actions to mitigate future heatwave stress in sensitive cities.
越来越多的人暴露在热浪中,这威胁着公众健康,并在未来几十年对各个社会经济部门提出挑战。以往的研究大多通过研究气温持续时间来关注特定地区发生的热浪,而忽视了热浪通常席卷大片地区的事实。为了全面评估热浪的影响,我们利用中国 321 个城市中超过 1000 万条有地理位置的微博数据集,共同分析了公众对热浪的关注。考虑到空间上的差异,我们设计了两种城市级别的公众关注度,即与高温相关的微博数量(NHTs)和与高温相关的微博比例(RHTs),分别表示热浪影响的严重程度和地点。热累积强度被用作热浪的替代值,它与 RHTs 的相关性比 NHTs 更为显著。多尺度地理加权回归(MGWR)模型用于研究环境、人口和经济社会因素的时空变化。六个城市群的 MGWR 系数与中国七个地理分区一致。这项研究为公众利用地理定位的社会传感数据关注热浪提供了新的视角和方法,并强调了采取行动减轻敏感城市未来热浪压力的必要性。
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引用次数: 0
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International journal of applied earth observation and geoinformation : ITC journal
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