Summary Software tools for opening, viewing, filtering, and analyzing Mala Geoscience RAMAC (http://ramac.malags.com) ground-penetrating radar (GPR) data. These tools are programmed using ITT Visual Information Solutions (ITT VIS) (formerly Research Systems, Inc. (RSI)) Interactive Data Language (IDL) for use within IDL or ITT VIS Environment for Visualizing Images (ENVI) software.
... Preprocessing of GPR data is necessary to produce quality images with clearly-visible reflection horizons. Mala Geoscience "GroundVision" software, used to acquire and display GPR data from the RAMAC instrument, has filtering capabilities that can dramatically improve the appearance of data when properly applied. Unfortunately, however, these filters are for display purposes only and cannot be permanently applied to the data or saved to a new output file, preventing any post-processing on the filtered data such as digitizing reflection horizons in other image-processing applications. To circumvent this limitation, we have simulated the GroundVision filters based on their description in the manual into a programming environment that allows the user to save the results for subsequent processing and data analysis.
The following filters are included:
1. Subtract Mean Trace: Removes horizontal banding within the radargram by subtracting a calculated mean trace from all traces. A "trace" is a single, vertical column of GPR data, representing the signal "traced" by radar pulses as they travel from the instrument into the subsurface and back. Horizontal banding is caused by "ringing" of the radar signal (negative and positive perturbations of signal strength) that results from interference between the transmitting and receiving signals since some of the transmission travels straight from the transmitter to the nearby receiver antenna (i.e. the "direct wave").
2. Time- (Depth-) Varying Gain: Because of geometrical spreading, the radar signal decreases in strength with depth as 1/r2, where r is depth. Each radar trace is multiplied by a gain function combining linear and exponential components, with coefficients set by the user, to correct for this loss of signal with depth.
3. DC Removal: There is often a constant offset in the amplitude of each radar trace caused by interference from direct current (DC) used to power the GPR instrument. This filter removes the DC component from the data, which has the effect of making the data less noisy.
In addition to filters, there are analysis tools that do the following:
1. Track the depth and distance of the current cursor location as it is moved over an image window of the radargram. Depth is computed based on the time window (in nanoseconds) of the data file and the ground velocity (in meters per nanosecond) of radar through the imaged subsurface medium/media.
2. Create an XYZ file (latitude, longitude, depth) of a linear feature identified within ENVI of one or more GPR and associated GPS data files. Such a file can be used to create a regularly-gridded data file that can then be visualized in three dimensions either in IDL/ENVI (iTools) or other applications.
3. Compute statistics (mean, minimum, maximum, standard deviation) for the depth of a linear feature identified within ENVI of one or more GPR data files. In addition, these depth statistics can also be expressed in terms of snow water equivalent (SWE) if the subsurface in the GPR data is snow/ice.
Multimedia Sample
View full image Caption Description:
GPR data before (left) and after (after) filtering.
View full image Caption Description:
Input widget for applying a time-varying gain filter.
View full image Caption Description:
Input widget for viewing depth and distance of each pixel.
View full image Caption Description:
Depth and snow water equivalent (SWE) stats for a GPR layer.
Service Citation
Originators:
John Maurer
Title:
Ground-Penetrating Radar (GPR) Interactive Data Language (IDL) Software Tools
Release_Date:
2006-07-26
Provider:
John Maurer
Edition:
1.0
URL:
http://gpr-idl-tools.sourceforge.net
Name:
JOHN
MAURER
Email:
JOHN.FROM.STL at STANFORDALUMNI.ORG
Service Provider Personnel
Name:
KONRAD
STEFFEN
Phone:
+1 (303) 492-4524
Email:
konrad.steffen at colorado.edu
Contact Address:
CIRES Ekeley Building, S264 City:
Boulder
Province or State:
CO
Postal Code:
80309-0216
Country:
USA
Distribution Media
Distribution_Media:
FTP
Distribution_Size:
102 KB
Distribution_Format:
ZIP
Fees:
0
Personnel
JOHN
MAURER Role:
TECHNICAL CONTACT
Role:
SERF AUTHOR
Email:
JOHN.FROM.STL at STANFORDALUMNI.ORG
Related URL
Link:
VIEW PROJECT HOME PAGE
Description:
Project home page on SourceForge.net, a website that hosts and distributes free and open source software applications. Includes program documentation and installation instructions, screenshots, a tutorial, and ability to download the software and example data files.
Link:
VIEW RELATED INFORMATION
Description:
A case study on the Greenland ice sheet using these software to analyze GPR data for subsurface snow stratigraphy and its spatial variability. This is the author's Masters thesis in the Department of Geography at the University of Colorado at Boulder with advisor Dr. Konrad Steffen. Citation:
Maurer, IV,, J.A. (2006), Local-scale snow accumulation variability on the Greenland ice sheet from ground-penetrating radar (GPR). Masters thesis, University of Colorado at Boulder. Available from http://cires.colorado.edu/~maurerj/gpr/gpr_cryosphere.html.
Publications/References Conyers, L. B. and D. Goodman (1997), Ground-Penetrating Radar: an Introduction for Archeologists. Walnut Creek, CA: AltaMira Press. 232 pp.
Maurer, IV,, J.A. (2006), Local-scale snow accumulation ... variability on the Greenland ice sheet from ground-penetrating radar (GPR). Masters thesis, University of Colorado at Boulder. Available from http://cires.colorado.edu/~maurerj/gpr/gpr_cryosphere.html.
Plewes, L.A. and B. Hubbard (2001), A review of the use of radio-echo sounding in glaciology. Progress in Physical Geography. 25(2): 203-236.
Siegert, M.J. (1999), On the origin, nature and uses of Antarctic ice-sheet radio-echo layering. Progress in Physical Geography. 23(2): 159-179.
Creation and Review Dates
SERF Creation Date:
2007-08-07
SERF Last Revision Date:
2007-08-09
Links
