Cross-island profiles were collected during spring 2004, continuing transect monitoring begun in 1995. Elevations are collected every 10m and at all significant elevation changes along transects that run at a 291/111 degree azimuth. Elevations were collected using a Trimble 5700 GPS total station and referenced to the NAVD88 datum. These data are used to monitor and understand the dynamics of barrier islands and their associated dune complexes.
In 1995, Assateague Island National Seashore initiated a long-term program to begin monitoring key aspects of island geomorphology. One of the goals of this program was the documentation of cross-island beach profile elevation on a biannual basis in order to describe and evaluate trends in island topographic relief and storm-driven change. For this purpose a profile network baseline was established in 1993 and expanded in 1995. Surface elevations are recorded along beach profile transects during the fall and spring of each year. Special transect sessions are conducted to document the effect of storms and for LIDAR ground truthing. Transects have also been performed in conjunction with wildlife studies. The dynamic nature of coastal barriers such as Assateague Island is a defining characteristic, influencing nearly every aspect of their ecology. Fundamentally disturbance driven systems, barrier islands and their endemic biota are continually shaped by physical forces on a time scale vastly accelerated in comparison to mainland systems. Because of the rapid pace and scope of change, long-term monitoring is crucial in understanding natural barrier island conditions as well as anthropogenic influences.
This is the first profile survey conducted entirely by GPS.
ground condition
None
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ASIS Cartographic Technician
Attributes are accurate as recorded in the field or within the tolerances set in Trimble Geomatics Office. There are no apparent inconsistencies in the attributes.
Horizontal and vertical accuracy checks were conducted over known monuments and error was found to be <0.005m horizontal and <0.010m vertical at all monuments. Data that did not meet RMS, PDOP, SNR and other criteria were discarded.
All points 10 m apart were collected except when these locations were obstructed or the signal degraded such that data could not be recorded.
Horizontal accuracy is reported as <0.015m. Positions with accuracy >0.015m are reported, however these positions are of suspect quality.
Vertical accuracy is reported as <0.015m. Positions with accuracy >0.015m are reported, however these positions are of suspect quality.
The profile network baseline, established by Taylor, Wisemann, and Taylor in 1993, and expanded by NPS personnel in 1995, was utilized for all data collection. Individual profile lines were numbered in consecutive order from north to south and prefaced in text by GPS or NPS, denoting whether the baseline monument was established by Taylor, Wisemann, Taylor, or NPS respectively. Spacing between GPS monuments is 2.0 km, with NPS monuments located approximately midway between GPS monuments. The result is a profile line density of 1 km along the northern 10 km of Assateague Island (commonly referred to as the "North End"), and a 2 km density for the remainder of the island. There are 22 profile transects collected. Profile surveys were conducted from each primary monument along a transect aligned to 291/11 degrees. Each transect extended from <0m oceanside to <0m bayside or up to the point where vegetation obstructed passage or degraded the radio signals and initialization was lost. The base station was set up on known monuments and all data collection was RTK. The base station occupied GPS3, GPS5, North Beach 2, GPS10, and GPS15. A Trimble 5700 total station was used to collect elevations. RTK collection was utilized with the base radio broadcasting at 25khz. Elevations were collected along the defined "stake-out" transect at 10 m intervals. Thus, elevations were taken at station 10, 20, 30 etc. Elevations were also shot at any significant change in elevation along the profile line. These points were calculated as staked-out points so that they fell on the line. The rover and base were set with an elevation mask of 12 degrees, SNR mask of 6.0, and PDOP mask of 6.0. Data was examined in Trimble Geomatics Office and exported as an xyz table. Data was also entered into the Profiles Database.
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Dataset copied.
Internal feature number.
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Feature geometry.
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point name
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Transect name
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Code for point
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Northing
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Easting
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Elevation
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Height above ellipsoid
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Year of collection
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Month of collection
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Day of month of collection
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Horizontal Datum
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Vertical datum
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Geoid model
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Horizontal Quality
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Vertical quality
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Horizontal Precision
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Vertical Precision
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root mean square
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Horizontal Dilution of Precision
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Rotational Dilution of Precision
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Vertical Dilution of Precision
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Number of GPS positions averaged for data
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Minimum number of satellites used in averaging
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major preceding weather events
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Dataset includes horizontal and vertical positional information and precious and quality descriptions of the data at those locations. The dataset also includes date information and information regarding the weather preceding data collection.
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