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.
Purpose:
The dataset was developed to monitor the distribution of eelgrass within the
Great Bay Estuary over time. The surveys have been completed yearly since 1986
to track trends over time. A final report on this project is available at:
https://scholars.unh.edu/prep/367/
Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 20160805
Currentness_Reference: Ground Date
Status:
Progress: Complete
Maintenance_and_Update_Frequency: Annually
Spatial_Domain:
Bounding_Coordinates:
West_Bounding_Coordinate: -70.911297
East_Bounding_Coordinate: -70.677157
North_Bounding_Coordinate: 43.153869
South_Bounding_Coordinate: 43.049923
Keywords:
Theme:
Theme_Keyword_Thesaurus: ISO 19115 Topic Category
Theme_Keyword: biota
Theme:
Theme_Keyword_Thesaurus: None
Theme_Keyword: Eelgrass
Theme:
Theme_Keyword_Thesaurus: None
Theme_Keyword: Estuary
Theme:
Theme_Keyword_Thesaurus: None
Theme_Keyword: Estuarine
Place:
Place_Keyword_Thesaurus: ISO 19115 Topic Category
Place_Keyword: oceans
Place_Keyword: Northeast
Place_Keyword: New England
Place_Keyword: New Hampshire
Place_Keyword: Great Bay
Place_Keyword: Little Harbor
Place_Keyword: Piscataqua River
Place_Keyword: Lamprey River
Place_Keyword: Oyster River
Place_Keyword: Bellamy River
Place_Keyword: Portsmouth Harbor
Place_Keyword: Squamscott River
Place_Keyword: New Castle
Place_Keyword: Rye
Place_Keyword: Portsmouth
Place_Keyword: Newington
Place_Keyword: Greenland
Place_Keyword: Stratham
Place_Keyword: Newfields
Place_Keyword: Newmarket
Place_Keyword: Durham
Place_Keyword: Dover
Place_Keyword: Madbury
Place_Keyword: Eliot
Place_Keyword: Kittery
Place_Keyword: Maine
Access_Constraints: None
Use_Constraints:
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.
These data are to be used for planning purposes only; distribution is discouraged.
Point_of_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Kalle Matso
Contact_Organization:
Piscataqua Region Estuaries Partnership, University of New Hampshire
Contact_Position: Science Program Manager
Contact_Address:
Address_Type: Mailing and Physical Address
Address: Nesmith Hall, 131 Main St.
City: Durham
State_or_Province: New Hampshire
Postal_Code: 03824
Contact_Voice_Telephone: 603-781-6591
Native_Data_Set_Environment:
Microsoft Windows XP Version 5.1 (Build 2600) Service Pack 2; ESRI ArcGIS 10.0.4.4000
Data_Quality_Information:
Logical_Consistency_Report:
Note that yearly variations in collection methods exist. Following is a
summary of methods that have been used.
The eelgrass habitat mapped from the aerial imagery is verified using the
ground truthing data by placing the ground-truthing locations onto the
digital image using GIS software. Ground-truthing is done from a small
boat during the same season as the photographs are taken. Ground-truth
observations are made at low tide or at other tide stages using a drop
camera. Positions are determined using GPS. Gaps, overlapping polygon areas
and duplicate polygons are identified and removed.
Completeness_Report: The dataset is complete. There are no known omissions.
Lineage:
Process_Step:
Process_Description:
The final photomosaics were received in December, 2016, from Kappa Mapping.
These were added to a GIS along with field information and other data layers
to aid in photointerpretation. Eelgrass beds were first outlined and screen
digitized using the GIS software packages, QGIS, and saved to an ESRI shape
file. Digitizing was generally done at a screen scale of 1:1000 or greater.
The minimum mapping unit for the delineation of eelgrass features was generally
100 square meters. However, smaller features were included in the dataset if they
could be clearly discerned as pure eelgrass beds.The projection used was New Hampshire
State Plane, NAD83, and the units were feet.
Process_Date: 20170305
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Kalle Matso
Contact_Organization:
Piscataqua Region Estuaries Partnership, University of New Hampshire
Contact_Position: Science Program Manager
Contact_Address:
Address_Type: Mailing and Physical Address
Address: Nesmith Hall, 131 Main St.
City: Durham
State_or_Province: New Hampshire
Postal_Code: 03824
Contact_Voice_Telephone: 603-781-6591
Spatial_Data_Organization_Information:
Direct_Spatial_Reference_Method: Vector
Point_and_Vector_Object_Information:
SDTS_Terms_Description:
SDTS_Point_and_Vector_Object_Type: G-polygon
Point_and_Vector_Object_Count: 156
Spatial_Reference_Information:
Horizontal_Coordinate_System_Definition:
Planar:
Grid_Coordinate_System:
Grid_Coordinate_System_Name: State Plane Coordinate System 1983
Contact_Organization: Earth Systems Research Center, University of New Hampshire
Contact_Person: GRANIT Database Manager
Contact_Position: GRANIT Database Manager
Contact_Address:
Address_Type: mailing and physical address
Address: Morse Hall, University of New Hampshire
City: Durham
State_or_Province: NH
Postal_Code: 03824
Contact_Voice_Telephone: 603-862-1792
Contact_Facsimile_Telephone: 603-862-0188
Contact_Electronic_Mail_Address: granit@unh.edu
Hours_of_Service: 8:30AM-5PM. EST
Resource_Description: Downloadable Data
Distribution_Liability:
Digital data in NH GRANIT represent the efforts of the contributing agencies
to record information from the cited source materials. Earth Systems Research Center, under contract
to the NH Office of Strategic initiatives, and in consultation with cooperating agencies, maintains a
continuing program to identify and correct errors in these data. OSI, ESRC, and the cooperating agencies
make no claim as to the validity or reliability or to any implied uses of these data.
