Great Bay Estuary Eelgrass - 2016

The dataset shows the locations where eelgrass was observed in the Great Bay Estuary based on photointerpretation of orthophotography collected on August 5, 2016. The study area includes the following waterbodies: Great Bay, the mouth of the Squamscott River, the tidal portion of the Lamprey River, the tidal portion of the Oyster River, the tidal portion of the Bellamy River, the Piscataqua River and Portsmouth Harbor and its associated creeks. Vertical aerial photography was collected as digital 4-band imagery with a nominal 1 foot resolution using an Intergraph Digital Mapping Camera. Environmental conditions included a low-sun angle, low spring tide, low cloud cover, calm winds, no preceding rain events, and low turbidity in the water column. The eelgrass habitat mapped from the aerial imagery was verified using the ground truthing data from preselected locations and ad hoc locations chosen during the course of the field work. Ground truthing was done from a small boat during the same season as the photographs were taken. Ground truth observations were made on all tides using a drop camera with video recording capabilities and at low tide when visual observations were recorded. Positions were determined using high accuracy Trimble GeoXH and GeoXT GPS units and a Garmin Colorado 400c as a backup.本数据集基于2016年8月5日采集的正射影像（orthophotography）开展影像解译（photointerpretation），呈现了大湾河口湾（Great Bay Estuary）内观测到的鳗草（eelgrass）分布点位。本次研究涵盖的水体包括：大湾、斯夸姆斯科特河（Squamscott River）河口、兰普雷河（Lamprey River）感潮河段、奥伊斯特河（Oyster River）感潮河段、贝拉米河（Bellamy River）感潮河段、皮斯卡塔夸河（Piscataqua River）以及朴次茅斯港（Portsmouth Harbor）及其附属溪流水道。本次垂直航空摄影采用英特格拉夫（Intergraph）数字测绘相机采集，为标称分辨率1英尺的4波段数字影像。影像采集当日的环境条件如下：太阳高度角较低、处于低春潮时段、云量稀少、风力平稳、无前期降雨事件，且水体浊度较低。基于航空影像解译绘制的鳗草栖息地分布，通过预设调查点位与野外作业期间临时选定点位的地面实况调查（ground truthing）数据完成了精度核验。地面实况调查于影像采集同期开展，作业载体为小型船只。观测工作覆盖所有潮汐时段，采用具备视频录制功能的投放式相机采集数据，同时在低潮时段辅以人工目视观测记录。点位定位采用高精度Trimble GeoXH与GeoXT型GPS接收机，并以Garmin Colorado 400c作为备用定位设备。