Multispectral reflectance imagery collected from an unmanned aerial system over oyster reefs in the Bay of St. Louis near Gulfport, Mississippi from 2018-05-07 to 2018-05-11

This data comprises imagery collected from an unmanned aerial system (DJI M600 Matrice) over oyster reefs in the Bay of St. Louis near Gulfport, Mississippi from 2018-05-07 to 2018-05-11. This dataset was collected with the goal of observing water quality from a remote platform. In particular, the data was collected to see how well it correlates with the hyperspectral imagery collected from the same flights, and to see if the five bands provided can supply enough information to observe relevant phenomena. The imagery was collected using a MicaSense RedEdge sensor, a five-band sensor that produces an image for each band. The bands are blue, green, red, red edge, and near-infrared. Center wavelengths are 475 nm, 560 nm, 668 nm, 717 nm, and 840 nm. The bandwidth for each is 20, 20, 10, 10, and 40 nm, respectively. RedEdge field-of-view (FOV) is 47.9 degrees horizontal, 36.9 degrees vertical. All imagery contains latitude, longitude, and altitude information, along with other camera parameters that allow for imagery post-processing. The processed data has been converted into reflectance values, ranging from what should be 0.0 to 1.0. Due to limitations in the collection and the downwelling light sensor for the RedEdge, these values will be incorrect if the lighting has changed significantly. In general, this will be because of cloud cover. There is a small amount of solar irradiance change as well over the flight, although that change should not heavily impact the data for its intended use. To achieve the reflectance corrections, all images are adjusted for gain, exposure time, vignetting effects, and lens distortion. This code is based on MicaSense's processing tutorials and is available on request. Images are also individually orthorectified. As there are no tie points with which to mosaic the images, a Python script is used to project images individually on a flat surface using the position, altitude, and attitude of the sensor at the time of image capture. This code can also be supplied on request. Related dataset (processed hyperspectral) is available under GRIIDC Unique Dataset Identifier (UDI): MS.x839.000:0017 (DOI: 10.7266/MW2PRASF).本数据集包含2018年5月7日至2018年5月11日期间，于美国密西西比州格尔夫波特附近圣路易斯湾的牡蛎礁上空，通过DJI M600 Matrice型无人航空系统（unmanned aerial system）采集的影像数据。本数据集的采集目标为通过远程平台观测水质，具体而言，旨在探究该数据与同次飞行采集的高光谱影像（hyperspectral imagery）之间的相关性，同时验证所提供的5个光谱波段是否足以支撑相关现象的观测。本次影像采集采用MicaSense RedEdge传感器（MicaSense RedEdge），这是一款可针对每个波段分别生成影像的五波段传感器，其波段涵盖蓝光、绿光、红光、红边以及近红外波段，各波段中心波长分别为475 nm、560 nm、668 nm、717 nm与840 nm，带宽依次为20 nm、20 nm、10 nm、10 nm与40 nm。该传感器的视场（field-of-view, FOV）水平角度为47.9°，垂直角度为36.9°。所有影像均包含纬度、经度、高度信息，以及支持影像后处理的其他相机参数。处理后的数据已转换为反射率值，理论取值范围应为0.0至1.0。但由于采集过程及RedEdge传感器的下行辐照度传感器存在局限，当光照条件发生显著变化时，反射率值将出现偏差，此类偏差通常由云层覆盖导致。本次飞行过程中太阳辐照度存在小幅变化，但该变化不会对本数据集的预期应用造成显著影响。为完成反射率校正，所有影像均已针对增益、曝光时长、渐晕效应与镜头畸变进行校正。该校正代码基于MicaSense的处理教程编写，可应要求提供。所有影像均已完成单独正射校正。由于不存在可用于影像拼接的连接点，研究人员采用Python脚本，根据影像采集时刻传感器的位置、高度与姿态，将每张影像单独投影至平面。该脚本同样可应要求提供。相关数据集（已处理高光谱影像）的GRIIDC唯一数据集标识符（Unique Dataset Identifier, UDI）为MS.x839.000:0017，DOI编号为10.7266/MW2PRASF。