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A precise vertical network: Establishing new orthometric heights with static surveys in Florida tidal marshes

Surveying and Land Information Systems

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Abstract

Elevation differences on the order of 10 cm within Florida's marsh system influence major variations in tidal flooding and in the associated plant communities. This low elevation gradient combined with sea level fluctuation of 5-to-10 cm over decadel and longer periods can generate significant alteration and erosion of marsh habitats along the Gulf Coast. Knowledge of precise and accurate elevations in the marsh is critical to the efficient monitoring and management of these habitats. Global positioning system (GPS) technology was employed to establish six new orthometric heights along the Gulf Coast from which kinematic surveys into the marsh interior are conducted. The vertical accuracy achieved using GPS technology was evaluated using two networks with 16 vertical and nine horizontal NGS published high accuracy positions. New positions were occupied near St. Marks National Wildlife Refuge and along the coastline of Levy County and Citrus County. Static surveys were conducted using four Ashtech dual frequency P-code receivers for 45-minute sessions and a data logging rate of 10 seconds. Network vector lengths ranged from 4 to 64 km and, including redundant baselines, totaled over 100 vectors. Analysis includes use of the GEOID93 model with a least squares network adjustment and reference to the National Geodetic Reference System (NGRS). The static surveys show high internal consistency and the desired centimeter-level accuracy is achieved for the local network. Uncertainties for the newly established vertical positions range from 0.8 cm to 1.8 cm at the 95% confidence level. These new positions provide sufficient vertical accuracy to achieve the project objectives of tying marsh surface elevations to long-term water level gauges recording sea level fluctuations along the coast.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
A precise vertical network: Establishing new orthometric heights with static surveys in Florida tidal marshes
Series title:
Surveying and Land Information Systems
Volume
56
Issue:
4
Year Published:
1996
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Surveying and Land Information Systems
First page:
200
Last page:
211
Number of Pages:
12