Understanding stand structure and height-diameter relationship of trees provides very useful information to establish appropriate countermeasures for sustainable management of endangered forests. Populus euphratica, a...Understanding stand structure and height-diameter relationship of trees provides very useful information to establish appropriate countermeasures for sustainable management of endangered forests. Populus euphratica, a dominant tree species along the Tarim River watershed, plays an irreplaceable role in the sustainable development of regional ecology, economy and society. However, as the result of climate changes and human activities, the natural riparian ecosystems within the whole river basin were degraded enormously, particularly in the lower reaches of the river where about 320 km of the riparian forests were either highly degraded or dead. In this study, we presented one of the main criteria for the assessment of vitality of P. euphrafica forests by estimating the defoliation level, and analyzed forest structure and determined the height-diameter （height means the height of a tree and diameter means the diameter at breast height （DBH） of a tree） relationship of trees in different vitality classes （i.e. healthy, good, medium, senesced, dying, dead and fallen）. Trees classified as healthy and good ac- counted for approximately 40% of all sample trees, while slightly and highly degraded trees took up nearly 60% of total sample trees. The values of TH （tree height） and DBH ranged from 0-19 m and 0-125 cm, respectively. Trees more than 15 m in TH and 60 cm in DBH appeared sporadically. Trees in different vitality classes had different distribution patterns. Healthy trees were mainly composed more of relatively younger trees than of degraded tress. The height-diameter relationships differed greatly among tress in different vitality classes, with the coefficients ranging from 0.1653 to 0.6942. Correlation coefficients of TH and DBH in healthy and good trees were higher than those in trees of other vitality classes. The correlation between TH and DBH decreased with the decline of tree vitality. Our results suggested that it might be able to differentiate degraded P. euphratica trees from healthy trees by determining the height-diameter correlation coefficient, and the coefficient would be a new parameter for detecting degradation and assessing sustainable management of floodplain forests in arid regions. In addition, tree vitality should be taken into account to make an accurate height-diameter model for tree height prediction.展开更多
The study was conducted to develop height-diameter at breast height(HT-DBH) models for Alnus japonica in La Trinidad, Benguet,Philippines and evaluate their predictive capability.The six widely used nonlinear growth m...The study was conducted to develop height-diameter at breast height(HT-DBH) models for Alnus japonica in La Trinidad, Benguet,Philippines and evaluate their predictive capability.The six widely used nonlinear growth models that were selected in this study were the ChapmanRichards, Schnute, Modified logistic, Korf/Lundqvist,Weibull and Exponential. A total of 208 Alnus japonica trees were measured using standard diameter tape for DBH(1.3 m above the ground) and Vertex and transponder was used for the total height measurement. The performance of the developed models were evaluated using the fit statistics including coefficient of determination(R^2), root mean square error(RMSE), mean bias(ē), absolute mean difference(AMD), and Akaike Information Criterion(AIC). The lack-of-fit statistics was also performed for further evaluation of the performance of the models.Based on the evaluation criteria, all six models were able to determine the DBH-height relationships and fitted the data well. Using the rank analysis, the Weibull HT-DBH model had the best performance among the six commonly used nonlinear growth models. The results of this study will help forest managers especially in La Trinidad, Benguet to easily predict the total height using the Weibull model for Alnus japonica utilizing the DBH as the predicting variable.展开更多
Background： Measurements of tree heights and diameters are essential in forest assessment and modelling. Tree heights are used for estimating timber volume, site index and other important variables related to forest ...Background： Measurements of tree heights and diameters are essential in forest assessment and modelling. Tree heights are used for estimating timber volume, site index and other important variables related to forest growth and yield, succession and carbon budget models. However, the diameter at breast height （dbh） can be more accurately obtained and at lower cost, than total tree height. Hence, generalized height-diameter （h-d） models that predict tree height from dbh, age and other covariates are needed. For a more flexible but biologically plausible estimation of covariate effects we use shape constrained generalized additive models as an extension of existing h-d model approaches. We use causal site parameters such as index of aridity to enhance the generality and causality of the models and to enable predictions under projected changeable climatic conditions. Methods： We develop unconstrained generalized additive models （GAM） and shape constrained generalized additive models （SCAM） for investigating the possible effects of tree-specific parameters such as tree age, relative diameter at breast height, and site-specific parameters such as index of aridity and sum of daily mean temperature during vegetation period, on the h-d relationship of forests in Lower Saxony, Germany. Results： Some of the derived effects, e.g. effects of age, index of aridity and sum of daily mean temperature have significantly non-linear pattern. The need for using SCAM results from the fact that some of the model effects show partially implausible patterns especially at the boundaries of data ranges. The derived model predicts monotonically increasing levels of tree height with increasing age and temperature sum and decreasing aridity and social rank of a tree within a stand, The definition of constraints leads only to marginal or minor decline in the model statistics like AIC An observed structured spatial trend in tree height is modelled via 2-dimensional surface fitting. Conclusions： We demonstrate that the SCAM approach allows optimal regression modelling flexibility similar to the standard GAM but with the additional possibility of defining specific constraints for the model effects. The longitudinal character of the model allows for tree height imputation for the current status of forests but also for future tree height prediction.展开更多
Background： Generalized height-diameter curves based on a re-parameterized version of the Korf function for Norway spruce （Piceo abies （L.） Karst.）, Scots pine （Pinus sylvestris L.） and silver birch （Betula pe...Background： Generalized height-diameter curves based on a re-parameterized version of the Korf function for Norway spruce （Piceo abies （L.） Karst.）, Scots pine （Pinus sylvestris L.） and silver birch （Betula pendula Roth） in Norwa are presented. The Norwegian National Forest Inventory （NFI） is used as data base for estimating the model parameters. The derived models are developed to enable spatially explicit and site sensitive tree height imputatio in forest inventories as well as future tree height predictions in growth and yield scenario simulations. Methods： Generalized additive mixed models （gamm） are employed to detect and quantify potentially non-linear effects of predictor variables. In doing so the quadratic mean diameter serves as longitudinal covariate since stand ag as measured in the NFI, shows only a weak correlation with a stands developmental status in Norwegian forests. Additionally the models can be locally calibrated by predicting random effects if measured height-diameter pairs are available. Based on the model selection of non-constraint models, shape constraint additive models （scare） were fit tc incorporate expert knowledge and intrinsic relationships by enforcing certain effect patterns like monotonicity. Results： Model comparisons demonstrate that the shape constraints lead to only marginal differences in statistical characteristics but ensure reasonable model predictions. Under constant constraints the developed models predict increasing tree heights with decreasing altitude, increasing soil depth and increasing competition pressure of a tree. / two-dimensional spatially structured effect of UTM-coordinates accounts for the potential effects of large scale spatial correlated covariates, which were not at our disposal. The main result of modelling the spatially structured effect is lower tree height prediction for coastal sites and with increasing latitude. The quadratic mean diameter affects both the level and the slope of the height-diameter curve and both effects are positive. Conclusions： In this investigation it is assumed that model effects in additive modelling of height-diameter curves which are unfeasible and too wiggly from an expert point of view are a result of quantitatively or qualitatively limited data bases. However, this problem can be regarded not to be specific to our investigation but more general since growth and yield data that are balanced over the whole data range with respect to all combinations of predictor variables are exceptional cases. Hence, scare may provide methodological improvements in several applications by combining the flexibility of additive models with expert knowledge.展开更多
The effect of height on performance of the PZT/Ni cylindrical bilayered magnetoelectric （ME） com- posites was studied in situ in this paper. Multiple resonant peaks appear between 1 and 300 kHz frequency for cyl- in...The effect of height on performance of the PZT/Ni cylindrical bilayered magnetoelectric （ME） com- posites was studied in situ in this paper. Multiple resonant peaks appear between 1 and 300 kHz frequency for cyl- inders of different heights. The first resonance frequency does not change with the cylinder height decreasing, but the second and the third resonant frequencies increase. The first three resonant modes radial, first-order height are attributed to the cylinder resonance, and second-order height resonance, respectively. The appropriate size and resonance frequency were chosen to obtain the highest ME voltage coefficient when designing cylindrical bilayered magnetoelectric devices. This article provides reference to design cylindrical magnetoelectric devices.展开更多
Background: Information on the relationship between height and changes in serum lipids in children is scarce in Cameroon. The aim of this study is to determine prevalence of dyslipidemia with respect to age and gender...Background: Information on the relationship between height and changes in serum lipids in children is scarce in Cameroon. The aim of this study is to determine prevalence of dyslipidemia with respect to age and gender and assess the association between height increase and serum lipid changes in Cameroon children. Methods: This hospital-based cross-sectional analysis included 472 boys and 534 girls between the ages of 5 and 16 years. Body height, weight, and waist circumference (WC) of children were measured and z-scores calculated. Total cholesterol-TC, triglycerides-TG, low density lipoprotein cholesterol-LDL-C and high-density lipoprotein cholesterol-HDL-C concentrations in fasting blood samples were determined by enzymatic method using an automated clinical chemistry analyzer (RX Monaco, UK). Children were divided into increasing quartiles of height z-score. Multiple linear regression analysis was used to compare mean lipid concentrations across quartiles of height z-score after controlling for age, gender, body weight, WC and fasting blood glucose. Results: The prevalence of elevated TC and LDL-C were respectively 18.5% and 19.2% higher in girls than boys. Also, the prevalence of elevated TC and TG was highest among younger (5- to 9-year-old) girls and boys respectively. There was a significant decrease in mean TC (168.8 to 127.2 mg/dl;p p = 0.019) and LDL-C (91.1 to 69.4 mg/dl;p = 0.018) in boys;and a significant decrease in mean TC (171.2 to 144.7 mg/dl;p = 0.004) and HDL-C (62.8 to 28.7 mg/dl;p p = 0.053) and the decrease in TG (p = 0.211) and LDL-C (p = 0.732) in girls with increasing height were not significant. Conclusion: Serum lipids decreased with increasing height after controlling for different variables. This study indicates that short children have higher serum lipid concentrations and this may increase the risk of lipid disorders, which may persist into adulthood.展开更多
To enrich knowledge on the growth dynamics of commercial forest species in the Congo Basin, a study was conducted in Cameroon, within a community forest in savannah forest transition zone (Zone 1) and within FMU 10 05...To enrich knowledge on the growth dynamics of commercial forest species in the Congo Basin, a study was conducted in Cameroon, within a community forest in savannah forest transition zone (Zone 1) and within FMU 10 052 in dense semi-deciduous humid forest (Zone 2). It aimed to obtain, in 8 species, the height (H) of the tree from its diameter (D) more accessible: Entandophragma cylindricum (Meliacea), Eribroma oblongum, Sterculia rhinopetala et Triplochiton scleroxylon (Malvaceae);Erythrophleum suaveolens et Piptadeniastrum africanum (Fabaceae), Milicia excelsa (Moraceae) et Terminalia superba (Combretaceae). The destructive method was used. After felling and flushing out a tree, the dendrometric parameters were measured and/or calculated. In Zone 1, 6 species including T. scleroxylon were calibrated using 30 trees of each. In Zone 2, 45 trees of E. cylindricum, 99 of E. suaveolens and 82 of T. scleroxylon constituted the sample. At the 5% threshold (95% confidence interval), the height-diameter relationship is a linear model. In all species, the height of a tree is predicted by measuring its diameter through linear regression. In Zone 1 regression equation is: H(m) = 28.13 + 19.09 * D(m) for T. scleroxylon;H(m) = 12.35 + 30.38 * D(m) for S. rhinopetala;H(m) = 23.09 + 26.42 * D(m) for E. oblongum;H(m) = 14.86 + 20.92 * D(m) for P. africanum;H(m) = 14.98 + 24.78 * D(m) for T. superba and H(m) = 1.55 + 32.37 * D(m) for M. excelsa. In Zone 2, the relationship is: H(m) = 27.40 + 14.21 * D(m) for T. scleroxylon;H(m) = 7.79 + 20.18 * D(m) for E. cylindricum and H(m) = 20.08 + 9.74 * D(m) for E. suaveolens (probability associated with F < 0.0001). The influence of site parameters (biotic and abiotic) on the height-diameter relationship should be more studied in multilayers forests specifically in the Congo Basin.展开更多
利用光学和SAR遥感影像进行建筑高度估计对于理解城市形态和优化城市存量空间具有重要意义。然而,现有的数据集存在诸多局限:由于样本数量较少,难以满足基于深度学习的遥感信息提取需求,样本所覆盖的区域较为有限,无法提供足够的地理多...利用光学和SAR遥感影像进行建筑高度估计对于理解城市形态和优化城市存量空间具有重要意义。然而,现有的数据集存在诸多局限:由于样本数量较少,难以满足基于深度学习的遥感信息提取需求,样本所覆盖的区域较为有限,无法提供足够的地理多样性和空间特征代表性,特别是针对中国区域的大规模建筑高度数据集尤为缺乏。此外,数据集的开源性不足,限制了其在更广泛的研究中的应用和验证。为解决这些问题,本文构建了一个面向深度学习的基于Sentinel影像的建筑物高度数据集BHDSI(Building Height Estimation Dataset Based on Sentinel Imagery),该数据集涵盖了中国62个城市的中心城区,共有5606个样本,覆盖了城市,农村等场景,是目前中国区域覆盖面积最大的建筑高度数据集。该数据集包含哨兵一号和哨兵二号的遥感影像以及建筑高度的真实值,样本大小是256×256,相比于64×64大小的数据集,为建筑高度估计研究提供了一个重要的补充选择。相比其他数据集,该数据集具有样本数量大、覆盖范围广、可获取性、建筑高度分布合理等特点,能够更好地满足深度学习网络的训练需求。在此基础上,本文采用相同的深度学习网络对BHDSI数据集及其他类似数据集进行了评估,并对比了多个网络使用BHDSI数据集时在建筑高度回归任务中的表现,深入分析了各网络的优劣。结果表明,与其他数据集相比,BHDSI数据集在建筑高度回归任务中的表现更加优异。进一步分析发现,使用BHDSI数据集时,建筑高度较低的区域其估计精度相对较高。此外,U-Net解码器用于建筑高度估计网络训练能够取得更高的精度。综上,BHDSI数据集为未来建筑高度估计领域的研究提供了重要的支持。展开更多
基金supported by International Science & Technology Cooperation Program of China (2010DFA92720-12)the National Natural Science Foundation of China (31360200)+1 种基金the German Volkswagen Foundation Eco CAR Project (Az88497)the German Federal Ministry of Education and Research (BMBF) within the framework of the Su Ma Ri O Project (01LL0918D)
文摘Understanding stand structure and height-diameter relationship of trees provides very useful information to establish appropriate countermeasures for sustainable management of endangered forests. Populus euphratica, a dominant tree species along the Tarim River watershed, plays an irreplaceable role in the sustainable development of regional ecology, economy and society. However, as the result of climate changes and human activities, the natural riparian ecosystems within the whole river basin were degraded enormously, particularly in the lower reaches of the river where about 320 km of the riparian forests were either highly degraded or dead. In this study, we presented one of the main criteria for the assessment of vitality of P. euphrafica forests by estimating the defoliation level, and analyzed forest structure and determined the height-diameter （height means the height of a tree and diameter means the diameter at breast height （DBH） of a tree） relationship of trees in different vitality classes （i.e. healthy, good, medium, senesced, dying, dead and fallen）. Trees classified as healthy and good ac- counted for approximately 40% of all sample trees, while slightly and highly degraded trees took up nearly 60% of total sample trees. The values of TH （tree height） and DBH ranged from 0-19 m and 0-125 cm, respectively. Trees more than 15 m in TH and 60 cm in DBH appeared sporadically. Trees in different vitality classes had different distribution patterns. Healthy trees were mainly composed more of relatively younger trees than of degraded tress. The height-diameter relationships differed greatly among tress in different vitality classes, with the coefficients ranging from 0.1653 to 0.6942. Correlation coefficients of TH and DBH in healthy and good trees were higher than those in trees of other vitality classes. The correlation between TH and DBH decreased with the decline of tree vitality. Our results suggested that it might be able to differentiate degraded P. euphratica trees from healthy trees by determining the height-diameter correlation coefficient, and the coefficient would be a new parameter for detecting degradation and assessing sustainable management of floodplain forests in arid regions. In addition, tree vitality should be taken into account to make an accurate height-diameter model for tree height prediction.
基金support of the Forest Science and Technology Projects [Project Nos. 2013069D10-1819-AA03 and 2014068E10-1819-AA03] provided by the Korea Forest Service
文摘The study was conducted to develop height-diameter at breast height(HT-DBH) models for Alnus japonica in La Trinidad, Benguet,Philippines and evaluate their predictive capability.The six widely used nonlinear growth models that were selected in this study were the ChapmanRichards, Schnute, Modified logistic, Korf/Lundqvist,Weibull and Exponential. A total of 208 Alnus japonica trees were measured using standard diameter tape for DBH(1.3 m above the ground) and Vertex and transponder was used for the total height measurement. The performance of the developed models were evaluated using the fit statistics including coefficient of determination(R^2), root mean square error(RMSE), mean bias(ē), absolute mean difference(AMD), and Akaike Information Criterion(AIC). The lack-of-fit statistics was also performed for further evaluation of the performance of the models.Based on the evaluation criteria, all six models were able to determine the DBH-height relationships and fitted the data well. Using the rank analysis, the Weibull HT-DBH model had the best performance among the six commonly used nonlinear growth models. The results of this study will help forest managers especially in La Trinidad, Benguet to easily predict the total height using the Weibull model for Alnus japonica utilizing the DBH as the predicting variable.
文摘Background： Measurements of tree heights and diameters are essential in forest assessment and modelling. Tree heights are used for estimating timber volume, site index and other important variables related to forest growth and yield, succession and carbon budget models. However, the diameter at breast height （dbh） can be more accurately obtained and at lower cost, than total tree height. Hence, generalized height-diameter （h-d） models that predict tree height from dbh, age and other covariates are needed. For a more flexible but biologically plausible estimation of covariate effects we use shape constrained generalized additive models as an extension of existing h-d model approaches. We use causal site parameters such as index of aridity to enhance the generality and causality of the models and to enable predictions under projected changeable climatic conditions. Methods： We develop unconstrained generalized additive models （GAM） and shape constrained generalized additive models （SCAM） for investigating the possible effects of tree-specific parameters such as tree age, relative diameter at breast height, and site-specific parameters such as index of aridity and sum of daily mean temperature during vegetation period, on the h-d relationship of forests in Lower Saxony, Germany. Results： Some of the derived effects, e.g. effects of age, index of aridity and sum of daily mean temperature have significantly non-linear pattern. The need for using SCAM results from the fact that some of the model effects show partially implausible patterns especially at the boundaries of data ranges. The derived model predicts monotonically increasing levels of tree height with increasing age and temperature sum and decreasing aridity and social rank of a tree within a stand, The definition of constraints leads only to marginal or minor decline in the model statistics like AIC An observed structured spatial trend in tree height is modelled via 2-dimensional surface fitting. Conclusions： We demonstrate that the SCAM approach allows optimal regression modelling flexibility similar to the standard GAM but with the additional possibility of defining specific constraints for the model effects. The longitudinal character of the model allows for tree height imputation for the current status of forests but also for future tree height prediction.
基金supported by the Norwegian Institute of Bioeconomy Research(NIBIO)
文摘Background： Generalized height-diameter curves based on a re-parameterized version of the Korf function for Norway spruce （Piceo abies （L.） Karst.）, Scots pine （Pinus sylvestris L.） and silver birch （Betula pendula Roth） in Norwa are presented. The Norwegian National Forest Inventory （NFI） is used as data base for estimating the model parameters. The derived models are developed to enable spatially explicit and site sensitive tree height imputatio in forest inventories as well as future tree height predictions in growth and yield scenario simulations. Methods： Generalized additive mixed models （gamm） are employed to detect and quantify potentially non-linear effects of predictor variables. In doing so the quadratic mean diameter serves as longitudinal covariate since stand ag as measured in the NFI, shows only a weak correlation with a stands developmental status in Norwegian forests. Additionally the models can be locally calibrated by predicting random effects if measured height-diameter pairs are available. Based on the model selection of non-constraint models, shape constraint additive models （scare） were fit tc incorporate expert knowledge and intrinsic relationships by enforcing certain effect patterns like monotonicity. Results： Model comparisons demonstrate that the shape constraints lead to only marginal differences in statistical characteristics but ensure reasonable model predictions. Under constant constraints the developed models predict increasing tree heights with decreasing altitude, increasing soil depth and increasing competition pressure of a tree. / two-dimensional spatially structured effect of UTM-coordinates accounts for the potential effects of large scale spatial correlated covariates, which were not at our disposal. The main result of modelling the spatially structured effect is lower tree height prediction for coastal sites and with increasing latitude. The quadratic mean diameter affects both the level and the slope of the height-diameter curve and both effects are positive. Conclusions： In this investigation it is assumed that model effects in additive modelling of height-diameter curves which are unfeasible and too wiggly from an expert point of view are a result of quantitatively or qualitatively limited data bases. However, this problem can be regarded not to be specific to our investigation but more general since growth and yield data that are balanced over the whole data range with respect to all combinations of predictor variables are exceptional cases. Hence, scare may provide methodological improvements in several applications by combining the flexibility of additive models with expert knowledge.
基金supported by the Beijing Nova Program(No.Z141103001814006)the National Key Technology R&D Program(Nos.2012BAC12B05 and 2012BAC02B01)+1 种基金the National Natural Science Foundation of China(Nos.51174247 and U1360202)the National High-Tech Research and the Development Program of China(No.2012AA063202)
文摘The effect of height on performance of the PZT/Ni cylindrical bilayered magnetoelectric （ME） com- posites was studied in situ in this paper. Multiple resonant peaks appear between 1 and 300 kHz frequency for cyl- inders of different heights. The first resonance frequency does not change with the cylinder height decreasing, but the second and the third resonant frequencies increase. The first three resonant modes radial, first-order height are attributed to the cylinder resonance, and second-order height resonance, respectively. The appropriate size and resonance frequency were chosen to obtain the highest ME voltage coefficient when designing cylindrical bilayered magnetoelectric devices. This article provides reference to design cylindrical magnetoelectric devices.
文摘Background: Information on the relationship between height and changes in serum lipids in children is scarce in Cameroon. The aim of this study is to determine prevalence of dyslipidemia with respect to age and gender and assess the association between height increase and serum lipid changes in Cameroon children. Methods: This hospital-based cross-sectional analysis included 472 boys and 534 girls between the ages of 5 and 16 years. Body height, weight, and waist circumference (WC) of children were measured and z-scores calculated. Total cholesterol-TC, triglycerides-TG, low density lipoprotein cholesterol-LDL-C and high-density lipoprotein cholesterol-HDL-C concentrations in fasting blood samples were determined by enzymatic method using an automated clinical chemistry analyzer (RX Monaco, UK). Children were divided into increasing quartiles of height z-score. Multiple linear regression analysis was used to compare mean lipid concentrations across quartiles of height z-score after controlling for age, gender, body weight, WC and fasting blood glucose. Results: The prevalence of elevated TC and LDL-C were respectively 18.5% and 19.2% higher in girls than boys. Also, the prevalence of elevated TC and TG was highest among younger (5- to 9-year-old) girls and boys respectively. There was a significant decrease in mean TC (168.8 to 127.2 mg/dl;p p = 0.019) and LDL-C (91.1 to 69.4 mg/dl;p = 0.018) in boys;and a significant decrease in mean TC (171.2 to 144.7 mg/dl;p = 0.004) and HDL-C (62.8 to 28.7 mg/dl;p p = 0.053) and the decrease in TG (p = 0.211) and LDL-C (p = 0.732) in girls with increasing height were not significant. Conclusion: Serum lipids decreased with increasing height after controlling for different variables. This study indicates that short children have higher serum lipid concentrations and this may increase the risk of lipid disorders, which may persist into adulthood.
文摘To enrich knowledge on the growth dynamics of commercial forest species in the Congo Basin, a study was conducted in Cameroon, within a community forest in savannah forest transition zone (Zone 1) and within FMU 10 052 in dense semi-deciduous humid forest (Zone 2). It aimed to obtain, in 8 species, the height (H) of the tree from its diameter (D) more accessible: Entandophragma cylindricum (Meliacea), Eribroma oblongum, Sterculia rhinopetala et Triplochiton scleroxylon (Malvaceae);Erythrophleum suaveolens et Piptadeniastrum africanum (Fabaceae), Milicia excelsa (Moraceae) et Terminalia superba (Combretaceae). The destructive method was used. After felling and flushing out a tree, the dendrometric parameters were measured and/or calculated. In Zone 1, 6 species including T. scleroxylon were calibrated using 30 trees of each. In Zone 2, 45 trees of E. cylindricum, 99 of E. suaveolens and 82 of T. scleroxylon constituted the sample. At the 5% threshold (95% confidence interval), the height-diameter relationship is a linear model. In all species, the height of a tree is predicted by measuring its diameter through linear regression. In Zone 1 regression equation is: H(m) = 28.13 + 19.09 * D(m) for T. scleroxylon;H(m) = 12.35 + 30.38 * D(m) for S. rhinopetala;H(m) = 23.09 + 26.42 * D(m) for E. oblongum;H(m) = 14.86 + 20.92 * D(m) for P. africanum;H(m) = 14.98 + 24.78 * D(m) for T. superba and H(m) = 1.55 + 32.37 * D(m) for M. excelsa. In Zone 2, the relationship is: H(m) = 27.40 + 14.21 * D(m) for T. scleroxylon;H(m) = 7.79 + 20.18 * D(m) for E. cylindricum and H(m) = 20.08 + 9.74 * D(m) for E. suaveolens (probability associated with F < 0.0001). The influence of site parameters (biotic and abiotic) on the height-diameter relationship should be more studied in multilayers forests specifically in the Congo Basin.
文摘利用光学和SAR遥感影像进行建筑高度估计对于理解城市形态和优化城市存量空间具有重要意义。然而,现有的数据集存在诸多局限:由于样本数量较少,难以满足基于深度学习的遥感信息提取需求,样本所覆盖的区域较为有限,无法提供足够的地理多样性和空间特征代表性,特别是针对中国区域的大规模建筑高度数据集尤为缺乏。此外,数据集的开源性不足,限制了其在更广泛的研究中的应用和验证。为解决这些问题,本文构建了一个面向深度学习的基于Sentinel影像的建筑物高度数据集BHDSI(Building Height Estimation Dataset Based on Sentinel Imagery),该数据集涵盖了中国62个城市的中心城区,共有5606个样本,覆盖了城市,农村等场景,是目前中国区域覆盖面积最大的建筑高度数据集。该数据集包含哨兵一号和哨兵二号的遥感影像以及建筑高度的真实值,样本大小是256×256,相比于64×64大小的数据集,为建筑高度估计研究提供了一个重要的补充选择。相比其他数据集,该数据集具有样本数量大、覆盖范围广、可获取性、建筑高度分布合理等特点,能够更好地满足深度学习网络的训练需求。在此基础上,本文采用相同的深度学习网络对BHDSI数据集及其他类似数据集进行了评估,并对比了多个网络使用BHDSI数据集时在建筑高度回归任务中的表现,深入分析了各网络的优劣。结果表明,与其他数据集相比,BHDSI数据集在建筑高度回归任务中的表现更加优异。进一步分析发现,使用BHDSI数据集时,建筑高度较低的区域其估计精度相对较高。此外,U-Net解码器用于建筑高度估计网络训练能够取得更高的精度。综上,BHDSI数据集为未来建筑高度估计领域的研究提供了重要的支持。
