Assessing the accuracy of regional LiDAR-based biomass estimation using a simulation approach
Assessing the accuracy of regional LiDAR-based biomass estimation using a simulation approach
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DOI：
10.1016/j.rse.2012.04.017
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发表时间：
2012-08-01
影响因子：
13.5
通讯作者：
Nelson, Ross
中科院分区：
文献类型：
--
作者：
Ene, Liviu Theodor;Naesset, Erik;Nelson, Ross
为了满足日益增长的对可靠和及时的木材资源和碳储量估算在中间和地方决策层面的需求，提出了一种使用机载激光扫描（ALS）作为条带采样工具的采样方法，作为传统的基于实地的国家森林清查系统的补充。这个想法导致了在挪威海德马克县进行的大规模生物质调查项目，面积为27390公里(2)。野外生物量估计值由挪威NFI提供，ALS测量值采用系统（SYS）设计在平行条带中获得。在基于设计和基于模型的推理框架下，使用回归估计器进行基于als的生物量估计。当涉及复杂设计时，评估推理有效性的一种可能方法是使用抽样模拟器，其中人工总体代表“基本真理”，并通过模拟抽样调查估计器的性质。为了创建人工种群，使用拟合经验观测值的copula函数生成包含NFI现场观测值和ALS指标的大型多元数据集，然后使用卫星图像和最近邻插值在研究区域内进行概化。通过模拟抽样研究了几种基于设计的模型辅助方差估计器和基于模型的方差估计器的性质，并比较了基于als和基于地面的无替换简单随机抽样（SRSwoR）和SYS设计下的方差估计器的精度。仿真结果表明，基于als的调查在基于设计和基于模型的框架下得出了有效的推理。方差估计器在两阶段SRSwoR下表现良好，但实际标准误差在两阶段SYS下被高估了约4.7倍。与纯地面库存相比，基于als的估计的估计标准误差大约大1.8倍，而实际精度（就均方根误差而言）提高了59%。(C) 2012爱思唯尔公司版权所有。
To meet the increasing need for reliable and timely timber resources and carbon stock estimates at intermediate and local decision levels, a sampling approach using airborne laser scanning (ALS) as a strip sampling tool has been proposed as a supplement to the conventional field-based National Forest Inventory system. This idea led to a large-scale biomass survey project undertaken in Hedmark County, Norway, an area encompassing 27390 km(2). The field biomass estimates were provided by the Norwegian NFI, and the ALS measurements were acquired in parallel strips using a systematic (SYS) design. The ALS-based biomass estimation was performed using regression estimators under design-based and the model-based inferential frameworks. A possible approach to assess the validity of inference when complex designs are involved is to use a sampling simulator where an artificial population represents the 'ground truth' and the properties of the estimators are investigated via simulated sampling. To create the artificial population, a large multivariate dataset containing NFI field observations and ALS metrics was generated using a copula function fitted to the empirical observations, and then it was generalized over the study area using satellite imagery and nearest: neighbor imputations. The properties of several design-based model-assisted and model-based variance estimators were investigated using simulated sampling and the accuracy of ALS-based and ground-based estimates under simple random sampling without replacement (SRSwoR) and SYS designs were compared. The simulation results indicated that the ALS-based survey produced valid inference under design-based and model-based frameworks. The variance estimators performed well under two-phase SRSwoR, but the real standard errors were overestimated approximately 4.7 times under two-phase SYS. Compared to the pure ground-based inventories, the estimated standard errors of the ALS-based estimates were approximately 1.8 times larger, while the real accuracy (in terms of root mean squared error) improved with 59%. (C) 2012 Elsevier Inc. All rights reserved.