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The data are available for the areas shown on the USGS High Accuracy Elevation Data graphic at <https://sofia.usgs.gov/exchange/desmond/desmondelev.html>.
Desmond, Greg, 2007, High Accuracy Elevation Data - Lake Okeechobee Littoral Zone: U.S. Geological Survey, Reston, VA.
Planar coordinates are encoded using Coordinate Pair
Abscissae (x-coordinates) are specified to the nearest 400
Ordinates (y-coordinates) are specified to the nearest 400
Planar coordinates are specified in meters
The horizontal datum used is North American Datum of 1983.
The ellipsoid used is Geodetic Reference System 80.
The semi-major axis of the ellipsoid used is 6378137.
The flattening of the ellipsoid used is 1/298.257.
If new data were added to the quadrangle, the revision date was modified for ALL points in the quadrangle to reflect the latest revision date. At the completion of data collection, the individual quad-based files were aggregated to create the larger files now available for download. (Source: USGS)
GPS data converted to ESRI shapefile by Susan D. Price. Data collection done by Charles Henkle and Ed Cyran as USGS contractors.
703 648-5056 (voice)
This project performed 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.
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 have 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) are being collected in critical areas using state-of-the-art differential global positioning system (GPS) technology and data processing techniques.
1.Collection of GPS XYZ points and vegetation classification in the Lake Okeechobee Littoral Zone using the helicopter-based Airborne Height Finder (AHF) developed by the USGS.
2. The GPS data were processed into an ASCII list of NAD83 geographic XY coordinates, NAVD88 elevation Z value and descriptor attribute data. This file was transformed using Corpscon, version 5.11.08 from the U.S. Army Corps of Engineers to NAD83 UTM XY and NAVD88 Z coordinates. The file was output as an ASCII text file and processed at USGS in Reston, VA.
3. The x,y, and z values of the ASCII text file were reformatted to the decimal value of 100th of meter (centimeter) to represent the accuracy of the data and then imported into ArcGIS 9.1 to create an ESRI shapefile.
4. The ESRI shapefile was compressed into a .zip file using WinZip. The associated .dbf files were opened in MS Excel and saved as the comma separated value file which also is available for download.
Person who carried out this activity:
703 648 6692 (voice)
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.
All verified and accepted data points are included in the files for each area
Are there legal restrictions on access or use of the data?
- Access_Constraints: none
- None. Acknowledgement of the U.S. Geological Survey would be appreciated for products derived from these data.
727 803-8747 ext 3028 (voice)
727 803-2030 (FAX)
Helicopter - Airborne Height Finder
No warrantees are implied or explicit for the data
|Data format:||comma separated values file of Global Positioning System (GPS) points in format ASCII .csv Size: 0.261|
|Data format:||ArcGIS shapefile and associated files in format zip (version unknown) shp.zip Size: 0.109|
727 803-8747 ext 3028 (voice)
727 803-2030 (FAX)
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