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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >ENHANCED DISCRIMINATION OF BOREAL FOREST COVERS WITH DIRECTIONAL REFLECTANCES FROM THE AIRBORNE POLARIZATION AND DIRECTIONALITY OF EARTH REFLECTANCES (POLDER) INSTRUMENT
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ENHANCED DISCRIMINATION OF BOREAL FOREST COVERS WITH DIRECTIONAL REFLECTANCES FROM THE AIRBORNE POLARIZATION AND DIRECTIONALITY OF EARTH REFLECTANCES (POLDER) INSTRUMENT

机译：通过空中极化和地球反射（测向）仪器的方向性增强对具有方向反射的北林覆盖物的区分

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During the Boreal Ecosystem-Atmosphere Study (BOREAS), directional and spectral reflectance measurements were acquired from May to July 1994 with the polarization and directionality of Earth reflectances (POLDER) instrument on board a NASA C-130 aircraft. The instrument has a wide field-of-view optics, a two-dimensional CCD array, and a rotating wheel carrying filters in the visible and near infrared. Measurements were obtained (1) over coniferous forests at the young and old jack pine and old black spruce sites, (2) over a deciduous forest at the old aspen site, and (3) over a fen at the fen site. A prominent hot spot feature was apparent at each site, with an additional strong peak in the specular direction for the fen site. Strong variations of the bidirectional reflectance distribution function (BRDF) with sun zenith angle were observed. For a constant sun zenith angle, the variation of the BRDF of conifer stands between May and July was relatively weak. A key objective of this paper is to quantify the improvement of discrimination of various forest covers when remotely sensed directional signatures are added to the more conventional spectral signatures. The experimental protocol consisted of the following steps. First, 150 pixels pertaining to five different classes of forest covers were selected on land cover maps available in the BOREAS Information System (BORIS) data base. Second, the BRDF measurements acquired by POLDER at each pixel were adjusted against a three-parameter semiempirical BRDF model and processed to retrieve the reflectance seen in three different viewing directions. Third, the results of supervised classifications were compared on all selected pixels, using as input, either the reflectances in only one direction (this simulates the case of conventional spectral signatures), or reflectances acquired in three directions (this simulates the case of spectral + directional signatures). The results showed that when only one spectral band was used, the proportion of correctly classified pixels increased from 36-59% with one viewing direction to 64-84% with three viewing directions. When three spectral bands were considered, this proportion improved from 72-87% to 83-97%. These results demonstrate that the account of directional information enhances the ability to discriminate forest covers by remote sensing. [References: 31]
机译：在北方生态系统-大气研究（BOREAS）期间，1994年5月至1994年7月使用NASA C-130飞机上的地球反射率的极化和方向性（POLDER）仪器进行了方向和光谱反射率的测量。该仪器具有宽视场光学器件，二维CCD阵列以及在可见光和近红外线中装有滤光片的旋转轮。在以下位置获得了测量值：（1）在老少皆宜的松树和老黑云杉站点的针叶林上，（2）在老白杨站点的落叶林上，以及（3）在站点的上。在每个站点上都有一个明显的热点特征，在fen站点的镜面方向上还有一个强峰值。观察到双向反射率分布函数（BRDF）随太阳天顶角的强烈变化。对于恒定的太阳天顶角，针叶林BRDF的变化在5月至7月之间相对较弱。本文的主要目的是量化在将遥感方向性特征添加到更常规的光谱特征中时，改善各种森林覆盖率的辨别力的方法。实验方案包括以下步骤。首先，在BOREAS信息系统（BORIS）数据库中可用的土地覆盖图上，选择了与五种不同森林覆盖率有关的150个像素。其次，针对三参数半经验BRDF模型调整POLDER在每个像素处获取的BRDF测量值，并进行处理以获取在三个不同观察方向上看到的反射率。第三，将所有选定像素的监督分类结果进行比较，使用输入作为一个输入，或者仅在一个方向上的反射率（这模拟常规光谱特征的情况），或者在三个方向上获取的反射率（这模拟光谱+光谱的情况）定向签名）。结果表明，当仅使用一个光谱带时，正确分类的像素的比例从一个观察方向的36-59％增加到三个观察方向的64-84％。当考虑三个光谱带时，该比例从72-87％提高到83-97％。这些结果表明，方向性信息的解释增强了通过遥感区分森林覆盖的能力。 [参考：31]

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