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Transient Electromagnetic Sounding Data

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Metadata:


Identification_Information:
Citation:
Citation_Information:
Originator: Dave Fitterman
Publication_Date: 2005
Title: Transient Electromagnetic Sounding Data
Geospatial_Data_Presentation_Form: text files
Online_Linkage: <https://sofia.usgs.gov/exchange/fitterman/fitterTEM.html>
Description:
Abstract:
This data set contains time-domain electromagnetic (TEM) soundings collected at 63 sites in and near Everglades National Park. The data set includes the sounding name, date measured, location information in the form of a descriptive location, zone 17 UTM coordinates, and latitude and longitude, transmitter loop size [meters], and location of receiver coil with respect to the center of the transmitter loop, layered-earth model best fitting the data. This includes the layer resistivity [ohm-meters] and layer thickness [meters]. Also included is the percentage rms misfit error between the observed and calculated apparent resistivity of the model.
Purpose:
The purpose of the work was to locate the freshwater-saltwater interface (FWSWI), and to provide data used to remove calibration errors in helicopter electromagnetic data. These data can be used to estimate formation resistivity as a function of depth to depths of up to 100 meters below the surface. This information is a value in determining if the aquifer is freshwater or saltwater saturated.
Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 19950817
Ending_Date: 19961210
Currentness_Reference: ground condition
Status:
Progress: Complete
Maintenance_and_Update_Frequency: None planned
Spatial_Domain:
Bounding_Coordinates:
West_Bounding_Coordinate: -81.1
East_Bounding_Coordinate: -80.4
North_Bounding_Coordinate: 25.5
South_Bounding_Coordinate: 25.15
Keywords:
Theme:
Theme_Keyword_Thesaurus: none
Theme_Keyword: salinity
Theme_Keyword: pore fluid resistivity
Theme_Keyword: airborne electromagnetic survey
Theme_Keyword: transient electromagnetic soundings
Theme_Keyword: hydrology
Theme_Keyword: salt water
Theme_Keyword: fresh water
Theme_Keyword: mapping
Theme_Keyword: geography
Theme:
Theme_Keyword_Thesaurus: ISO 19115 Topic Category
Theme_Keyword: environment
Theme_Keyword: geoscientificInformation
Theme_Keyword: inlandWaters
Theme_Keyword: 007
Theme_Keyword: 008
Theme_Keyword: 012
Place:
Place_Keyword_Thesaurus:
Department of Commerce, 1995, Countries, Dependencies, Areas of Special Sovereignty, and Their Principal Administrative Divisions, Federal Information Processing Standard (FIPS) 10-4, Washington, DC, National Institute of Standards and Technology
Place_Keyword: United States
Place_Keyword: US
Place:
Place_Keyword_Thesaurus:
U.S. Department of Commerce, 1987, Codes for the identification of the States, the District of Columbia and the outlying areas of the United States, and associated areas (Federal Information Processing Standard 5-2): Washington, DC, NIST
Place_Keyword: Florida
Place_Keyword: FL
Place:
Place_Keyword_Thesaurus:
Department of Commerce, 1990, Counties and Equivalent Entities of the United States, Its Possessions, and Associated Areas, FIPS 6-3, Washington, DC, National Institute of Standards and Technology
Place_Keyword: Monroe County
Place:
Place_Keyword_Thesaurus: USGS Geographic Names Information System
Place_Keyword: Shark River Slough
Place_Keyword: Taylor Slough
Place:
Place_Keyword_Thesaurus: none
Place_Keyword: Central Everglades
Stratum:
Stratum_Keyword_Thesaurus: none
Stratum_Keyword: surficial aquifer
Stratum_Keyword: Biscayne aquifer
Access_Constraints: none
Use_Constraints: none
Point_of_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: David Fitterman
Contact_Organization: U.S. Geological Survey
Contact_Position: Project Chief
Contact_Address:
Address_Type: mailing address
Address:
P. O. Box 25046

Denver Federal Center MS 964

City: Denver
State_or_Province: CO
Postal_Code: 80225
Country: USA
Contact_Voice_Telephone: 303 236-1382
Contact_Facsimile_Telephone: 303 236-1425
Contact_Electronic_Mail_Address: fitter@usgs.gov
Browse_Graphic:
Browse_Graphic_File_Name: <https://sofia.usgs.gov/exchange/fitterman/locationTEM.html>
Browse_Graphic_File_Description: sounding locations for TEM data
Browse_Graphic_File_Type: GIF
Native_Data_Set_Environment: ASCII text files
Cross_Reference:
Citation_Information:
Originator:
Fitterman. David

Deszcz-Pan, Maria

Publication_Date: 199907
Title:
Geophysical Mapping of Saltwater Intrusion in Everglades National Park
Geospatial_Data_Presentation_Form: report
Series_Information:
Series_Name: Proceedings
Issue_Identification: 3rd International Symposium on Ecohydraulics
Publication_Information:
Publication_Place: Salt Lake City, UT
Publisher: International Association for Hydraulic Research (IAHR)
Online_Linkage: <https://sofia.usgs.gov/publications/papers/geophysmap/>
Cross_Reference:
Citation_Information:
Originator:
Stewart, M. A.

Bhatt, T. N., Fennema, R. J., Fitterman, D. V.

Publication_Date: 2002
Title:
The Road to Flamingo: an Evaluation of Flow Pattern Alterations and Salinity Intrusion in the Lower Glades, Everglades National Park
Geospatial_Data_Presentation_Form: report
Series_Information:
Series_Name: USGS Open-File Report
Issue_Identification: OFR 02-59
Publication_Information:
Publication_Place: Reston, VA
Publisher: U.S. Geological Survey
Online_Linkage: <https://sofia.usgs.gov/publications/ofr/02-59>
Cross_Reference:
Citation_Information:
Originator:
Fitterman, David V.

Deszcz-Pan, Maria

Publication_Date: 2002
Title:
Helicopter Electromagnetic Data from Everglades National Park and Surrounding Areas, Florida: Collected 9-14 December 1994
Geospatial_Data_Presentation_Form: report
Series_Information:
Series_Name: USGS Open-File Report
Issue_Identification: 02-101
Publication_Information:
Publication_Place: Reston, VA
Publisher: U.S. Geological Survey
Online_Linkage: <https://sofia.usgs.gov/publications/ofr/02-101/>
Cross_Reference:
Citation_Information:
Originator:
Fitterman, David V.

Deszcz-Pan, Maria; Stoddard, Carl E.

Publication_Date: 1999
Title:
Results of Time-Domain Electromagnetic Soundings in Everglades National Park, Florida
Geospatial_Data_Presentation_Form: report
Series_Information:
Series_Name: USGS Open-File Report
Issue_Identification: 99-426
Publication_Information:
Publication_Place: Reston, VA
Publisher: U.S. Geological Survey
Online_Linkage: <https://sofia.usgs.gov/publications/ofr/99-426/>
Cross_Reference:
Citation_Information:
Originator:
Fitterman, David V.

Deszcz-Pan,, Maria

Publication_Date: 2004
Title:
Characterization of Saltwater Intrusion in South Florida Using Electromagnetic Geophysical Methods
Geospatial_Data_Presentation_Form: report
Series_Information:
Series_Name: Proceedings
Issue_Identification: 18th Salt Water Intrusion Meeting
Publication_Information:
Publication_Place: Cartagena, Spain
Publisher: unknown
Online_Linkage: <https://sofia.usgs.gov/publications/papers/sw_intrusion_sfl/>
Cross_Reference:
Citation_Information:
Originator:
Fitterman, D. V.

Deszcz-Pan M.

Publication_Date: 2001
Title:
Saltwater intrusion in Everglades National Park, Florida measured by airborne electromagnetic surveys
Geospatial_Data_Presentation_Form: report
Series_Information:
Series_Name: proceedings
Issue_Identification:
First Internationl Conference on Saltwater Intrusion and Coastal Aquifers-Monitoring, Modeling, and Management (SWICA-M3
Publication_Information:
Publication_Place: Essaouira, Morocco
Publisher: Labratoire d'Analyse des Systemes Hydrauliques (LASH)
Online_Linkage: <https://sofia.usgs.gov/publications/papers/sltwtr_intrusn/>
Cross_Reference:
Citation_Information:
Originator:
Fitterman, D.V.

Deszcz-Pan, M.

Publication_Date: 2001
Title:
Using airborne and ground electromagnetic data to map hydrologic features in Everglades National Pak
Geospatial_Data_Presentation_Form: report
Series_Information:
Series_Name: Proceedings
Issue_Identification:
Symposium on the Application of Geophysics to Engineering and Environmental Problems SAGEEP
Publication_Information:
Publication_Place: Denver, Co
Publisher: Environmental and Engineering Geophysical Society
Online_Linkage: <https://sofia.usgs.gov/publications/papers/map_hydrofeat/>

Data_Quality_Information:
Logical_Consistency_Report: not applicable
Completeness_Report: not applicable
Lineage:
Process_Step:
Process_Description:
The techniques used in this study rely upon time-varying magnetic fields from a transmitter to induce electrical currents into the ground. The flow of these currents is controlled by the electrical conductivity of the ground. More conductive zones tend to let the induced currents flow unimpeded, while less conductive zones impede the current flow. The induced currents in the ground produce a secondary magnetic field which is recorded by a receiver coil. Analysis of the received signals determines how conductivity (or its reciprocal, resistivity) varies with depth and position.

The transient electromagnetic (TEM) sounding method uses the transition from a steady to zero transmitter current to induce current in the ground. The ground response is measured during the transmitter off-time. We employed a 40-m by 40-m transmitter loop with the receiver coil located at the center of the transmitter loop. The data are converted to apparent resistivity before modeling. Layered-earth model parameters are determined using commercially available nonlinear least-squares inversion software. Because of the large number of data points (typically 25-35) compared to the 10 for each HEM measurement, model parameter estimates are more reliable for the TEM data than the HEM data. The TEM method also has the ability to probe to greater depths than the HEM method. From these data we were able to locate the FWSWI, as well as the depth to the base of the Biscayne aquifer.

Using the TEM method in the Everglades required slight modification of standard methods as most of the soundings were made in water-covered areas. Equipment had to be floated in plastic tubs, and the transmitter wire was strung over saw grass, while the receiver coil was stood on long legs to keep it above the water.

At the few sites where we had observation wells, induction logs were measured. The induction tool uses a frequency-domain electromagnetic system to determine the formation resistivity outside the borehole. The borehole must be cased with non-conducting material such as PVC. Induction logs provide very detailed resistivity-depth information within the vicinity of the borehole about 1 m radius from the well. This information is useful in determining the relationship between formation resistivity and pore water quality.

Time-domain electromagnetic (TEM) soundings were made using a Geonics PROTEM system. A square transmitter loop measuring approximately 40 meters on a side was used. The loop was connected to a Geonics EM-47 transmitter which produced a 50-percent duty-cycle square wave. The current in the transmitter loop creates a primary magnetic field. When the transmitter current is interrupted, the decaying primary magnetic field induces a circulating current flow in the ground below the transmitter loop. The decay of this induced current system is controlled by the electrical resistivity of the ground below the transmitter loop.

The decaying current system produces a secondary magnetic field, which is sensed by a receiver coil located at the center of the transmitter loop and recorded by the receiver. The recorded signal is called a transient. Many transients are recorded and averaged to reduce noise in the data and to estimate measurement error. The averaged data are converted to apparent resistivity to allow comparison of one sounding to another.

The data are modeled as one-dimensional, layered-earth models. The electrical resistivity and thickness of model layers is determined by least-squares parameter estimation.

Process_Date: Unknown
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: David Fitterman
Contact_Organization: U.S. Geological Survey
Contact_Position: Project Chief
Contact_Address:
Address_Type: mailing address
Address:
P. O. Box 25046

Denver Federal Center MS 964

City: Denver
State_or_Province: CO
Postal_Code: 80225
Country: USA
Contact_Voice_Telephone: 303 236-1382
Contact_Facsimile_Telephone: 303 236-1425
Contact_Electronic_Mail_Address: fitter@usgs.gov

Spatial_Data_Organization_Information:
Indirect_Spatial_Reference: southwest Florida coast
Direct_Spatial_Reference_Method: Point
Point_and_Vector_Object_Information:
SDTS_Terms_Description:
SDTS_Point_and_Vector_Object_Type: Entity point
Point_and_Vector_Object_Count: 63

Spatial_Reference_Information:
Horizontal_Coordinate_System_Definition:
Geographic:
Latitude_Resolution: 1
Longitude_Resolution: 0.1
Geographic_Coordinate_Units: Decimal degrees
Geodetic_Model:
Horizontal_Datum_Name: North American Datum of 1983
Ellipsoid_Name: Geodetic Reference System 80
Semi-major_Axis: 6378137
Denominator_of_Flattening_Ratio: 298.257

Entity_and_Attribute_Information:
Overview_Description:
Entity_and_Attribute_Overview:
The time-domain electromagnetic (TEM) data were collected in and near Everglades National Park. The TEM data sets contain all necessary information required for data interpretation. The data were recorded using a Geonics PROTEM receiver and EM-47 transmitter.

The data set includes the following information:

1. Sounding name

2. Date measured

3. Location information in the form of: a descriptive location, zone 17 UTM coordinates, and lattitude and longitude.

4. Transmitter loop size [meters] and location of receiver coil with respect to the center of the transmitter loop.

5. Layered-earth model best fitting the data. This includes the layer resistivity [ohm-meters] and layer thickness [meters]. Also included is the percentage rms misfit error between the observed and calculated apparent resistivity of the model.

6. Information on the measurement system including: the TEM system used, the repetition frequency [hertz] of the transmitted waveform, the data set code (Used by interpretation software to represent the repetition frequency.), the transmitter current [amperes], the length of the transmitter turnoff ramp [microseconds], the receiver coil area-turns product [turns-meters2], and the receiver gain setting. The actual receiver gain is 52.1x2G, where G is the gain setting.

7. Apparent resistivity-time data are provided for two base frequencies: the higher base-frequency data are on the left hand side and the lower base-frequency data on the right hand side. For each frequency the following information is given:

* the time of the measurement point after transmitter turn off [milliseconds]; * the measured apparent resistivity [ohm-meters]; * the estimate measurement error [percent]; * a mask code which indicates if the data were used (u) in the least-squares parameter estimation, masked (m) from the parameter estimation but retained for possible inclusion in modeling, or deleted (d) from the parameter estimation because the observation error was too large; * and the apparent resistivity calculated for the best-fit model.

Entity_and_Attribute_Detail_Citation: USGS personnel

Distribution_Information:
Distributor:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Heather S.Henkel
Contact_Organization: U.S. Geological Survey
Contact_Address:
Address_Type: mailing address
Address: 600 Fourth St. South
City: St. Petersburg
State_or_Province: FL
Postal_Code: 33701
Country: USA
Contact_Voice_Telephone: 727 803-8747 ext 3028
Contact_Facsimile_Telephone: 727 803-2030
Contact_Electronic_Mail_Address: hhenkel@usgs.gov
Resource_Description: Transient Electromagnetic Data
Distribution_Liability: The data have no implied or explicit guarantees
Standard_Order_Process:
Digital_Form:
Digital_Transfer_Information:
Format_Name: ASCII text
Format_Version_Number: unknown
Format_Information_Content:
Individual files contain data for one site; or the data may be downloaded as one file
Transfer_Size: 0.2
Digital_Transfer_Option:
Online_Option:
Computer_Contact_Information:
Network_Address:
Network_Resource_Name: <https://sofia.usgs.gov/exchange/fitterman/fitterTEM.html>
Access_Instructions: Data may be downloaded from the SOFIA web site
Fees: None

Metadata_Reference_Information:
Metadata_Date: 20070507
Metadata_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Heather Henkel
Contact_Organization: U.S. Geological Survey
Contact_Address:
Address_Type: mailing and physical address
Address: 600 Fourth Street South
City: St. Petersburg
State_or_Province: FL
Postal_Code: 33701
Country: USA
Contact_Voice_Telephone: 727 803-8747 ext 3028
Contact_Facsimile_Telephone: 727 803-2030
Contact_Electronic_Mail_Address: sofia-metadata@usgs.gov
Metadata_Standard_Name: Content Standard for Digital Geospatial Metadata
Metadata_Standard_Version: FGDC-STD-001-1998

This page is <https://sofia.usgs.gov/metadata/sflwww/fitter.html>

U.S. Department of the Interior, U.S. Geological Survey, Center for Coastal Geology
Comments and suggestions? Contact: Heather Henkel - Webmaster
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