vector digital data https://nhgeodata.unh.edu/hosting/rest/services/Hosted/CV_BiologyAndEcology/FeatureServer/34 https://ftp.granit.unh.edu/GRANIT_Data/Vector_Data/Biology_and_Ecology/eelgrass/2025/ The dataset shows the locations where eelgrass was observed within 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, and the coastal shore of Odiorne Point. Image processing and photointerpretation was completed on orthophotography collected via UAV, as well as Go-Pro imagery from fixed wing aircraft and Sentinel satellite imagery. Vertical UAV imagery was collected as five spectral bands inclusive of RGB, Red-Edge ,and Near Infrared bands. Imagery was collected with varying 2.0 to 6.0 cm spatial resolutions based on 100 to 400 ft flight altitudes specific to FAA maximum flight restrictions around the Pease International Tradeport. Areal Go-Pro RGB vertical aerial imagery was collected on October 9th, 2025. The Sentinel satellite imagery was acquired for the date of July 29th, 2025 with a nominal 10 meter spatial resolution. Environmental conditions, included a low-sun angle, low tides, low cloud cover, and low turbidity in the water column were maintained throughout the course of the survey. 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 a high accuracy GPS unit.Database file attributes for the 2025 survey are as follows: “id,” a unique consecutive number; “Hectares,” the area of the polygon in hectares; “Acres,” the area of the polygon in acres; “Year,” equal to 2025, the year of the imagery used, “Label” for the assessment zone, and “type” to distinguish between polygons mapped as at least 10% eelgrass (type = 1), at least 10% widgeon grass (type = 3), or at least 10% eelgrass and at least 10% widgeon grass (type = 2), “Confidence,” a measure of cartographer confidence (H = Higher, M = Medium, L = Lower) of the existence and/or cover type of vegetation per polygon. “Notes,” a text field listing the types of imagery used and/or mapping limitations per polygon as observed by the cartographer. Note that sparse eelgrass areas with < 10% cover (type =0) are also recorded within the "Type" field (attribute), but do not meet the >= 10% cover threshold to be counted towards eelgrass totals within the study. The dataset was developed to monitor the distribution of eelgrass within the Great Bay Estuary over time. With the exception of 2018 and 2020, surveys have been completed yearly since 1986 to track trends over time. None Eliot Kittery Newington Piscataqua River Newfields Rye New Hampshire Portsmouth Harbor New England Estuarine Portsmouth Durham Great Bay Greenland Bellamy River oceans Stratham Squamscott River biota Oyster River Little Harbor Northeast Eelgrass Newmarket Estuary Maine Madbury Lamprey River Dover New Castle Odiorne Point (Rye) None User is required to read metadata completely before using the data. The information provided in this coverage was developed by an independent contractor and used by the NH Department of Environmental Services (NHDES). Development of these databases is an ongoing project; they may not contain all existing and potential sites, stations, or threats. The NHDES is not responsible for the use or interpretation of this information, or for any inaccuracies in the site names or locations. All information is subject to verification. Distribution is discouraged. Microsoft Windows 7 Version 6.1 (Build 7601) Service Pack 1; Esri ArcGIS 12.4.0.19948 Vector GT-polygon composed of chains 0 2025-eelgrass-Locations2-w-zones FID Internal feature number. Esri Sequential unique whole numbers that are automatically generated. Shape Feature geometry. Esri Coordinates defining the features. FID_2025_e Hectares Acres Year Name Confidence Notes Type LABEL FID_GreatB OBJECTID LABEL_1 Shape_Leng Shape_Area Area of feature in internal units squared. Esri Positive real numbers that are automatically generated. 20260401 FGDC Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998 local time