Folders: ROOT > ScienceBase Catalog > USGS Lower Mississippi-Gulf Water Science Center > @ Lake and Reservoir Studies > Geophysical surveys and geospatial data for Bob Kidd Lake, Washington County, Arkansas > Frequency Domain Electromagnetic Data ( Show direct descendants )
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ROOT _ScienceBase Catalog __USGS Lower Mississippi-Gulf Water Science Center ___@ Lake and Reservoir Studies ____Geophysical surveys and geospatial data for Bob Kidd Lake, Washington County, Arkansas _____Frequency Domain Electromagnetic Data Filters
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FDEM Methodology For this project frequency domain electromagnetic (FDEM) data were collected with a GEM-2, a broadband, multifrequency, fixed-coil electromagnetic induction unit (Geophex, 2015). Both in-phase and quadrature data were collected on 15 channels from a frequency of 810 Hz to 66,090 Hz. This system was carried along profiles that followed the axis of the dam and along tie lines that were perpendicular to the axis of the dam. Each data point was located using a backpack mounted GPS. To correct the drift of the instrument, a base station was established on the east side of the dam. Each survey started and ended with an occupation of the base station. These occupations occur as even line numbers...
Categories: Data
FDEM Processing The frequency domain electromagnetic (FDEM) data were downloaded from the GEM-2 instrument and aggregated into a single data file. The data were manually despiked and smoothed to remove negative values and the effects of metallic objects. A drift correction was applied by finding the average in-phase and average quadrature values for each frequency transmitted each time the base station was occupied. This average value was then used to calculate a linear trend of the data in time and the linear trend was subtracted from the data set. After the data were drift corrected, the data was leveled by calculating the arithmetic mean of the survey data subtracting that value from the dataset to level...
Categories: Data
FDEM Processing The frequency domain electromagnetic (FDEM) data were downloaded from the GEM-2 instrument and aggregated into a single data file. The data were manually despiked and smoothed to remove negative values and the effects of metallic objects. A drift correction was applied by finding the average in-phase and average quadrature values for each frequency transmitted each time the base station was occupied. This average value was then used to calculate a linear trend of the data in time and the linear trend was subtracted from the data set. After the data were drift corrected, the data was leveled by calculating the arithmetic mean of the survey data subtracting that value from the dataset to level...
Categories: Data
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