High Accuracy Elevation Data - Water Conservation Areas and Greater Everglades RegionEntry ID: USGS_SOFIA_HAED_WCA_Everglades
Abstract: The High Accuracy Elevation Data Project collected elevation data (meters) on a 400 meter topographic grid with a vertical accuracy of +/- 15 centimeters to define the topography in South Florida. The data are referenced to the horizontal datum North American Datum 1983 (NAD 83) and the vertical datum North American Vertical Datum 1988 (NAVD 88). In some areas, the surveying was accomplished using ... airboats. Because access was a logistical problem with airboats, the USGS developed a helicopter-based instrument known as the Airborne Height Finder (AHF). All subsequent data collection used the AHF. Data were collected from the Loxahatchee National Wildlife Refuge, south through the Water Conservation Areas (1A, 2A, 2B, 3A, and 3B), Big Cypress National Park, the Everglades National Park, to the Florida Bay. The data are available for the areas shown on the USGS High Accuracy Elevation Data graphic at http://sofia.usgs.gov/exchange/desmond/desmondelev.html . The work was performed for Everglades ecosystem restoration purposes.
The data are from regional topographic surveys to collect and provide elevation data to parameterize hydrologic and ecological numerical simulation models that are being developed for ecosystem restoration activities. Surveying services were also rendered to provide vertical reference points for numerous water level gauges. Modeling of sheet flow and water surface levels in the wetlands of South Florida is very sensitive to changes in elevation due to the expansive and extremely low relief terrain. Hydrologists determined minimum vertical accuracy requirements for the elevation data for use as input to hydrologic models. As a result, elevation data with a vertical accuracy specification of +/-15 centimeters (cm) relative to the North American Vertical Datum of 1988 (NAVD88) were collected in critical areas using state-of-the-art differential global positioning system (GPS) technology and data processing techniques.
Data Set Citation
Dataset Originator/Creator: Greg Desmond
Dataset Title: High Accuracy Elevation Data - Water Conservation Areas and Greater Everglades Region
Dataset Release Date: 2007-10
Data Presentation Form: text files, shapefiles
Other Citation Details: Data collection done by C. Henkle, G. Shupe, B. Glover, E. Cyran, and G. Desmond of the USGS. Others include V. Caruso, G. Freeman, and S. Price.Online Resource: http://sofia.usgs.gov/exchange/desmond/desmondelev.html
Start Date: 1995-01-01Stop Date: 2007-12-31
Horizontal Resolution Range: 250 meters - < 500 meters
Vertical Resolution: .01
ISO Topic Category
Quality The Grossman Hammock and Perrine quadrangles have helicopter AHF & airboat and truck data.
All verified and accepted data points are included in the files for the area.
Horizontal positions are established by GPS observations and are referenced to the North American Datum of 1983 (NAD83). The desired horizontal accuracy is +/- 15 centimeters. ... This level of accuracy is consistent with GPS differential techniques which use two stations - a high-quality dual-frequency GPS receiver base station and a roving GPS station. The density and accuracy of a given GPS data observation varies from a few meters to a few centimeters according to the Position Dilution of Precision (PDOP) in the study area. Generally if the PDOP is observed to be excessive, data collection is discontinued or the data are discarded. The PDOP is an indicator of the positional accuracy of the GPS that be can derived from the current GPS satellite geometry, which varies continuously. Generally the smaller the PDOP number, the higher the data quality. The PDOP is a permanent part of the recorded data and is also included in the post processing procedures during reduction of the GPS observations to NAD 83. Where possible, the GPS base station has an ellipsoid height to an accuracy of two centimeters relative to the Continuously Operating Reference Stations (CORS) or the High Accuracy Reference Network (HARN), both operated by the National Geodetic Survey (NGS).
For all elevation data the vertical accuracy specification is +/- 15 centimeters and is referenced to NAVD 1988.
This elevation data is intended primarily for use in hydrological modeling. It is collected as high accuracy, "bare earth" ground elevation. That is, the data are restricted to ground elevations only. "Bare earth" in the Everglades swamp environment is generally considered to be the layer of "muck" which will support a one pound weight on a bearing surface of approximately 5.3 square inches (2.6 inch circle). In non-swamp areas it is actual bare ground.
Access Constraints None
Use Constraints Acknowledgement of the U.S. Geological Survey would be appreciated for products derived from these data.
Data Set Progress
Distribution Format: Compressed ESRI shapefile (.zip); Comma separated value file (.csv) or (.zip)
Role: TECHNICAL CONTACT
Email: rglover at usgs.gov
521 National Center
Province or State: VA
Postal Code: 20192
Role: DIF AUTHOR
Email: alicia.m.aleman at nasa.gov
Goddard Space Flight Center Code 610.2
Province or State: MD
Postal Code: 20771
Extended Metadata Properties
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Creation and Review Dates
DIF Creation Date: 2007-10-24
Last DIF Revision Date: 2008-12-31