Envir ONF — Dominant height

[link to description pdf](https://carto.ain.fr/webapps/externe/doc/ONF_notice_modeles_LiDAR_v2.pdf) 1 — Modeling principles The present models are constructed from the detection of the apex identified on the digital height model from the LiDAR covers. Only heights greater than 13 meters associated with bowls of more than 5 square meters are preserved. Treatment shall be carried out excluding the ‘unwooded’ type of the IFN stand mapping v.2. Each apex is classified as hardwood or soft based on the slopes of its hoop and its reflectance measured in SPOT 6 images. The diameters at 1.30 m and the increments are estimated by the characteristics of the bowl associated with the apex. At the pixel scale of 26.5 m on the side, the earth surfaces predicted for each tree are summed by species and categories of diameters. The results obtained are corrected according to linear models. Models applied to apex and pixels are calibrated using the forest observatory plots. They are validated on a new set of 240 plots of 15 meters radius measured in 2015 and independent of the calibration set. 2 — Validity of modeled parameters Generally, the validity of modeled parameters is not known for rare and atypical stands at the Ain Mountain scale. These stands are, for example, the plantations of larchs, the pine groves, the young leafy young leafy thinned... The validity in stands of black pine forests or sylvestres has not been verified. All data are for a pre-counting diameter of 17.5 cm to 1.30 m (unless otherwise stated). 3 — Precautions for the realisation of calculations based on the data of the rasters For basal area, production, stem density, stand types, zero values shall be used in the absence of data. These cases correspond either to stands less than 13 metres high (a priori composed of trees with a diameter of less than 17.5 centimeters), or to a type of non-wooded IFN stand. For stand types, the zero value is a non-pre-accountable stand, or an unforested area. For height, diameter and Gini values, the NULL value shall be used in the absence of data. The edge pixels incorporate on a part of their surface an unwooded area. In case the extraction area incorporates such pixels, it is important to apply to the extraction surface a negative buffer that will exclude its points.[link to description pdf](https://carto.ain.fr/webapps/externe/doc/ONF_notice_modeles_LiDAR_v2.pdf) 1 — 建模原理 本系列模型基于激光雷达（LiDAR）覆盖的数字高程模型上识别的树顶点构建。仅保留高度超过13米且对应冠幅斑块面积大于5平方米的对象。需排除法国国家森林清查（IFN）样地制图v.2中的“无林地”类型开展处理。每个树顶点将根据其冠层坡度以及SPOT 6卫星影像测得的反射率，被划分为阔叶树或针叶树。胸径（1.30米处）及其生长增量将通过与该顶点对应的冠幅斑块的特征进行估算。在边长为26.5米的像素尺度下，单木的预测冠幅投影面积将按树种及径阶进行汇总。所得结果将通过线性模型进行校正。针对树顶点与像素的建模方法，将利用森林监测样地进行校准，并在2015年测得的240个半径15米的独立于校准集的新样地中完成验证。 2 — 建模参数的有效性 总体而言，在安山（Ain）山地尺度下，稀有或非典型林分的建模参数有效性尚未明确。此类林分例如落叶松人工林、松树林分，以及经间伐的幼龄阔叶林。黑松林或欧洲赤松林分的参数有效性尚未得到验证。所有数据均对应1.30米处胸径17.5厘米的预统计标准（另有说明者除外）。 3 — 基于栅格数据开展计算的注意事项 对于林分断面积（basal area）、林分产量（production）、林分株数密度（stem density）及林分类型，若无对应数据则采用零值。此类无数据情况对应两类林分：一是树高不足13米（理论上胸径小于17.5厘米）的林分，二是法国国家森林清查（IFN）定义的非林地类型。针对林分类型而言，零值代表未纳入预统计的林分或无林地区域。对于树高、胸径及基尼系数（Gini），若无对应数据则采用空值（NULL）。边缘像元的部分区域为无林地。若提取区域包含此类边缘像元，则需对提取区域施加负缓冲区以排除这些像元对应的点位。