SPYSTUF hyperspectral data

The SPYSTUF hyperspectral data contains high spatial and spectral resolution Aisa Eagle II (visible to near infrared, 400-900 nm) airborne imaging spectrometer above a Hyytiälä forest research station hosting the SMEAR II (Station for Measuring Ecosystem-Atmosphere Relations, 61°50' N, 24°17' E) on 3 July 2015. The spectral resolution of the data is 4.6 nm, and the spatial resolution 0.6 m. The data are partly multiangular with the sensor tilted 30° off-nadir for two flight lines, resulting in measurements with the angle between the directions to the sensor and the sun of 19° (closest to hotspot), 55° (nadir) and 76° (dark spot). The data are processed to top-of-canopy geolocated reflectance factors and mosaicked. All mosaicked data were collected with the sensor pointing approximately nadir. The hyperspectral imagery is accompanied by data on basic forest variables and optical LAI from 20 plots in the image area, determined within appox. one week around the airborne acquisition. The data were obtained between 10:44 and 12:20 (GMT+3) at approximately 1 km altitude above the ground with flight lines consecutively in the northwestern and southeastern directions to minimize BRF effects. The Aisa Eagle II sensor had a field of view (FOV) of 37.5° divided between 1024 pixels. The average solar zenith angle was 48°, the photosynthetic photon flux density ranged from 1285 to 1493 μmol/(m^2*s) with a mean value of 1408 μmol/(m^2*s) (SMEAR II measurement data above the forest). The weather conditions were optimal for an airborne hyperspectral acquisition with a clear blue sky. The collection and processing of the dataset was largely funded by the Academy of Finland (project SPYSTUF, PI M. Mõttus, grants 266152, 272989 and 303633). All authors were affiliated with the University of Helsinki, Finland, during the data acquisition. Data processing was mostly performed by Vincent Markiet and Matti Mõttus at VTT Technical Research Centre of Finland. Data license: Creative Commons Attribution 4.0 International (CC BY 4.0)

SPYSTUF高光谱数据集包含了高空间和光谱分辨率的Aisa Eagle II（可见光至近红外，400-900 nm）机载成像光谱仪在Hyytiälä森林研究站（位于北纬61°50'，东经24°17'）上空，于2015年7月3日获取的数据。该数据的光谱分辨率为4.6 nm，空间分辨率为0.6 m。数据部分为多角度，传感器在两条飞行线中偏离垂直向下30°，导致测量方向与传感器和太阳之间的角度分别为19°（最接近热点）、55°（垂直向下）和76°（暗斑）。数据经处理得到冠层顶部地理定位的反射率因子和镶嵌图。所有镶嵌数据均由传感器指向约垂直向下采集。高光谱图像伴随着图像区域内20个样地的基本森林变量和光学叶面积指数数据，这些数据在机载数据获取前后大约一周内确定。数据在地面以上约1 km的高度，于GMT+3时区的10:44至12:20之间获取，飞行线依次为西北和东南方向，以最小化BRF效应。Aisa Eagle II传感器的视场（FOV）为37.5°，分为1024像素。平均太阳天顶角为48°，光合有效辐射通量密度范围为1285至1493 μmol/(m^2*s)，平均值约为1408 μmol/(m^2*s)（SMEAR II森林上空测量数据）。天气状况非常适合进行机载高光谱数据采集，天空晴朗。数据集的收集和处理主要得到芬兰科学院（项目SPYSTUF，负责人M. Mõttus，资助号266152、272989和303633）的资助。所有作者在数据采集期间均为芬兰赫尔辛基大学教职工。数据处理主要由芬兰VTT技术研究中心的Vincent Markiet和Matti Mõttus完成。数据许可证：Creative Commons Attribution 4.0 International (CC BY 4.0)。