Prepared in cooperation with the NorthPlatte, South Platte, and Twin Platte Natural 

Resource Districts, Nebraska

Airborne Geophysical Surveys Conducted in Western 

Nebraska, 2010—Contractor Reports and Data

By U.S.Geological Survey Crustal Geophysics and Geochemistry Science Center

Open-File Report 2013–1268

U.S. Department of the Interior

U.S. Geological Survey
ii

U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2014 

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Suggested citation: 

U.S. Geological Survey Crustal Geophysics and Geochemistry Science Center, 2014, Airborne geophysical 

surveys conducted in western Nebraska, 2010—Contractor reports and data: U.S. Geological Survey Open-File 

Report 2013–1268, 4 p., http://dx.doi.org/10.3133/ofr20131268. 

ISSN 2331-1258 (online)

Any use of trade, firm, or product names is for descriptive purposes only and does not imply 

endorsement by the U.S. Government. 

Although this information product, for the most part, is in the public domain, it also may contain

copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be 

secured from the copyright owner. 
iii

Contents

Executive Summary....................................................................................................................................................... 1

Appendixes.................................................................................................................................................................... 3

Appendix 1. Contractor Report Aarhus Geophysics/SkyTEM Canada, Inc.—Data Acquisition from 

Nebraska, USA .......................................................................................................................................................... 4

Report File: 20140203_Nebraska_Report_updated.pdf ......................................................................................... 4

Data File: 20100901_DataDelivery.zip ................................................................................................................... 4

Appendix 2. Contractor Reports, Aarhus Geophysics ApS—Data Processing and Inversion of SkyTEM Data, 

Nebraska, USA .......................................................................................................................................................... 4

Report File: SkyTEM USGS UTM13_complete.pdf ................................................................................................ 4

Report File: SkyTEM USGS UTM14_complete.pdf ................................................................................................ 4

Data File: ascii_files.zip.......................................................................................................................................... 4

Figure

1. SkyTEM Canada, Inc., survey flight lines, western Nebraska, flown in 2010............................................................ 2 
Airborne Geophysical Surveys Conducted in Western 

Nebraska, 2010—Contractor Reports and Data

By U.S. Geological Survey Crustal Geophysics and Geochemistry Science Center

Executive Summary

This report contains three contractor reports and data files for an airborne electromagnetic 

survey flown from June 28 to July 7, 2010. The first report; “SkyTEM Survey: Nebraska, USA, Data” 

describes data aquisition and processing from a time-domain electromagnetic and magnetic survey

performed by SkyTEM Canada, Inc. (the North American SkyTEM subsidiary), in western Nebraska, 

USA, (fig. 1). Digital data for this report are given in Appendix 1. The airborne geophysical data from 

the SkyTEM survey subsequently were processed and inverted by Aarhus Geophysics ApS, Aarhus, 

Denmark, to produce resistivity depth sections along each flight line. The result of that processing is 

described in two reports presented in Appendix 2, “Processing and inversion of SkyTEM data from 

USGS Area UTM–13” and “Processing and inversion of SkyTEM data from USGS Area UTM–14.” 

Funding for these surveys was provided by the North Platte Natural Resources District, the 

South Platte Natural Resources District, and the Twin Platte Natural Resources District, in Scottsbluff, 

Sidney, and North Platte, Nebraska, respectively. Any additional information concerning the 

geophysical data may be obtained from the U.S. Geological Survey Crustal Geophysics and 

Geochemistry Science Center, Denver, Colorado. 
2

Figure 1. Location of SkyTEM Canada, Inc., geophysical survey flight lines (shown in bright red) in western 

Nebraska. Also shown are natural resource districts which were cooperators in the airborne electromagnetic 

survey. Modified from SkyTEM Canada, Inc. contractor report (see Appendix1, this publication). [Abbreviations: 

AEM, airborne electromagnetic survey flightlines (already existing and shown here in bright blue); NRD, Natural 

Resource District; NPNRD, North Platte Natural Resources District; SPNRD, South Platte Natural Resources 

District; TPNRD, Twin Platte Natural Resources District] 
3

Appendixes
4

Appendix 1. Contractor Report Aarhus Geophysics/SkyTEM Canada, Inc.—Data Acquisition from 

Nebraska, USA

The contractor report provides details of project design and data acquisition over some 1900 km 

of flight lines in western Nebraska, including instrumentation and set-up, method(s) to synchronize data, 

calibration of the electromagnetic system (to accommodate differences between the North American 

power grid and the Danish National Reference site with its different grid frequency), and quality 

assurance for the data set. Protocols also describe data acquisition with detailed maps, weather reports, 

and base-station information. Application of the digital elevation model and data processing are 

discussed in detail. Location information from differential global positioning (DGPS) provided extreme 

accuracy and was used in data acquisition and as input to the processing flow. Residual magnetic field 

was the product of the processed data, from which total magnetic intensity was recalculated.

Similarly, the report presents all elements of the inversion and modeling of the Nebraska 

SkyTEM data. Inversion was performed as a regularized, damped, least-squares inversion along the 

profiles with a 1-D, 30-layer model. The inversion produced a model for approximately every 4 m along 

the flight line. Resulting models are presented as model sections (profiles) and as resistivity grids. 

Data files include the following:

Report File: 20140203_Nebraska_Report_updated.pdf (note: appendixes 4, 5, and 6 of this file are given 

in the data delivery file listed below, and appendix 7 describes the format for delivered digital data). 

Data File: 20100901_DataDelivery.zip (1.09 gigabytes). 

Appendix 2. Contractor Reports, Aarhus Geophysics ApS—Data Processing and Inversion of 

SkyTEM Data, Nebraska, USA

Processing and Inversion of SkyTEM Data from USGS Nebraska Area UTM–13 

Processing and Inversion of SkyTEM Data from USGS Nebraska Area UMT–14 

This appendix contains processed data and two sets of inversions and models in two geographic 

areas (listed above). Two contractor reports present data (in a separate zipped file) processed and 

inverted by Aarhus Geophysics ApS, Aarhus, Denmark, after data acquisition from airborne timedomain electromagnetic geophysical surveys in Nebraska in 2010, located within the UTM Zone–13 

and UTM Zone–14 reference meridians. Total processed line length was about 1890 km; included maps 

illustrate location of the lines. Full details of the processing and the subsequent inversion appear in 

reports for the UTM–13 and UTM–14 areas, respectively, including flight-line locations and profiles, 

inversion quality-control maps, and average resistivity maps at various depth intervals. Relevant file 

names include:

Report File: SkyTEM USGS UTM13_complete.pdf

Report File: SkyTEM USGS UTM14_complete.pdf

Data File: ascii_files.zip [data files]

Note that data appear as ascii-format files, in a file named ascii_files.zip (approximately 74

megbytes).

Files to accompany this report are provided electronically through links from the USGS 

Publications Warehouse web site. (See suggested citation, this report, for full URL address.)