Newsletter – June 2010
GPR-SLICE users,
I would like to welcome the following organizations:
1. OYO Corporation, Japan
2. Poyry Infra GmbH, Austria (www.poyry-infra.at)
3. City of Winder Water Department, Georgia
4. Earth Science and Resource Engineering, CSIRO, Australia ( www.csiro.au)
5. Coracle Associates Ltd, UK (www.coracle.co.uk)
6. Geology and Environmental Science, James Madison University, Virginia
7. Zonge Geosciences, Lakewood, (www.zonge.com)
8. Intec Corporation, League City, Texas
9. Federal Highways Research Center, McLean Virginia
10. Dept of Geosciences, University of Iowa
11. Spanish Council for Scientific Research, Merida, Spain (www.iam.csic.es)
12. SubTerra Geoservices, LLC, (www.subterrageo.com)
13. PROYECTO SAEC, University Complutense Madrid, Spain
14. Idaho National Laboratory – BEA, Idaho Falls
15. Geophysical Survey LLC, (www.geophysurvey.com)
Updates
 Differentiation of time slices added to Grid Filter Menu
 Multi-Channel Advancements and Integration:
3D Radar Geoscope multi-channel conversion *.vol format
IDS Stream + Terravision + Mala Mira auto info file integration
 Open GL Volume – fast texture mapping of displays of XYZ planes and
X,Y, XY, ANG radargrams
 Isosurface Statistics
 Improvements to auto hyperbola detection using nearby searching
 Compilation of auto hyperbola detected amplitudes for gridding
 New Button to remove Double GPS Scan #’s - Critical Option
GPR-SLICE V7.0 www.GPR-SURVEY.com
Differentiation of time slices added to Grid Filter Menu
Often subtle features are not illuminated in the standard time slice
images where interpolated and gridded square amplitudes/energy of the
reflected signals are displayed. To enhance small changes in the recorded
reflected amplitudes a variety of filters have been available in the Grid Filter
box, including boxcar subtraction etc. However, another useful filter of the
time slice images is to differentiate the image in both x and y directions. A
new option which differentiates the time slices has been added.
The
process looks at nearest neighbor differences, squaring the differences in
both x and y directions, and presenting the square root of this sum.
Figure 1. Example of a time slice that was differentiated using the dx+dy
filter. (The displays were made from the Pixel Map menu after processing).
GPR-SLICE V7.0 www.GPR-SURVEY.com
The data are normalized to 8 bit color. An example of the new dx+dy
differentiation filter is shown in Figure 1 with the original data, the
differentiated time slices, and a small lo pass filter applied to the
differentiated time slice. Very subtle structures which are not illuminated in
the regular time slice are apparent. Individual differentiation filters in both
the x and y directions are also available as well in the Grid Filter box.
Isosurface Statistics
Open GL Volume has recently been programmed to provide statistics on
displayed isosurfaces. A new button called “statistics” located below the
isosurface options, will generate a dialog giving the number of grid cells, and
the volume of these grid cells associated with the isosurface. The calculated
volume is a function of the nominal velocity of the site (set in the Options
menu).
Figure 2. Isosurface volume statistics are now available in the Open GL
Volume menu.
GPR-SLICE V7.0 www.GPR-SURVEY.com
In the example in Figure 2, which is the icon of GPR-SLICE software, a
6th century AD Japanese burial mound was detected beneath an alfalfa field
(http://www.gpr-survey.com/gprslice2.html). The destroyed burial mound,
still had a fully intact moat and a (collapsed) burial chamber inside the moat.
The volume of material detected in the moat and the chamber is 17.97 cubic
meters at the 50 percent isosurface setting. In this example, only the
volume in focus (from the much larger site surveyed) is shown with the
statistics. As a review or for those that did not discover these functions, on
the left hand side of the Open GL Volume menu, a focused volume can be
set. The six slots on the left-hand side of the menu are user defined regions
inside the XYZ volume. The first 2 settings are xstart/end, ystart/yend, and
zstart/zend where the Z values are defined in nanoseconds. This particular
isosurface displays examines data from the volume from 25-34.4 ns.
To
get the focused volume, the Focus checkbox needs to be clicked on. This
will cause Open GL Volume to reread the focused volume and put this into
memory for use in menu.
Improvements to Automatic Hyperbola Detection (for authorized
licenses)
Several important advancements for auto hyperbola detection were
added to the Hyperbola Search menu.
The earliest algorithm for auto
hyperbola detection provided for several years ago included an amplitude
threshold test along the radargram where at least N scans following
hyperbola needed to be breached in order for a detection to trigger. The
detection would also lay dormant for N-skipped scans before being turned on
again. The triggering of the first data in radargram that met the auto
hyperbola detection criteria could often slightly skew the results on the left
side of the hyperbola. An additional option call N-nearby was included in the
menu to tell the software to look out 1 additional scan and compare the peak
responses from the triggered location with several others. The N-nearby
option will compare the peak amplitude at the triggered location with 4
additional points: 1) point directly below the first triggered location in the
binary radargram at the found scan, 2) the point above and to the right in
the next radar scan, plus 3) the point at the same sample depth in the next
scan over, and 4) the point one lower in the scan in the next scan over.
Dramatic improvements in the peak amplitude response detected for the
auto hyperbola detection is found with the new option.
GPR-SLICE V7.0 www.GPR-SURVEY.com
Figure 3. Auto-hyperbola detection options shown in the Hyperbola Search
menu, and indicating the location of the new parameter N-nearby, allowing
for additional nearby scans to be included in the detection after initial
triggering.
A comparison of the recorded amplitudes is shown in Figure 3 where the Nnearby is 0 (= off) and for N-nearby set to 1 (=on).
The peak amplitude responses of the hyperbola from rebar are important
for estimating deterioration of concrete and rebar (for bridgedeck). As a
further development of auto hyperbola mapping and bridgedeck analysis,
the detected hyperbola amplitudes can get compiled and gridded in GPRSLICE. Shown in Figure 3 is the location of where to compile the hyperbola
amplitudes. In Figure 4 is the gridded hyperbola amplitude using the Grid
menu.
GPR-SLICE V7.0 www.GPR-SURVEY.com
Figure 4. Gridded amplitude map of the peak response of auto-detected
hyperbolas from a bridgedeck (data courtesy of Kevin Hon, Mala Geoscience)
Open GL Volume – Texture mapping method for enhanced
performance for displays of XYZ planes and X, Y, XY and Ang
radargrams
The “first” version of Open GL Volume was programmed with vertex
mapping. What this is involves, is sending every vertex in the binary
volume to Open GL for rendering. The color and the position of each vertex
is required. The performance of Open GL when every vertex is sent for
rendering significantly alters the performance of volume displays with they
are large.
An alternative method for showing plane XYZ displays is to use “texture”
mapping. In Open GL this refers to essentially generating an image of the
GPR-SLICE V7.0 www.GPR-SURVEY.com
plane and then immediately rendering it to its location in the 3D volume.
Texture mapping does not require sending every vertex color and its location
to Open GL for rendering. With texture mapping, since the number of
vertexes sent to Open GL is minimal, there is a significant enhanced
performance of displays of large datasets. An example of performance
improvement that Jimmy Adcock from GSB Prospection recently reported is
shown below:
Test data block: 835 x 730 x 55
Computer 1:
AMD Athlon64 X2 Dual Core Processor 5000+ 2.60GHz, 2.0GB RAM
Vista Home Basic (32bit) - SP2
Current v7.0 - One complete bounce (i.e. down and up) in Z plane = 2m57s
Beta v7.0 - First complete bounce in Z plane = 1m34s
Beta v7.0 - Subsequent completes bounces in Z plane = 15s
Computer 2:
Intel Core2 Extreme Quad Core Processor 2.53GHz, 8.0GB RAM
XP Professional (64bit)
Current v7.0 - One complete bounce (i.e. down and up) in Z plane = 41s
Beta v7.0 - First complete bounce in Z plane = ~4s
Beta v7.0 - Subsequent completes bounces in Z plane = ~2s
In a test that I ran on my computer for a 3D volume that was 182 mb
(1662x1002x56), the first bounce took 15 seconds and subsequent Z
bounces only 2 seconds. For the older vertex mapping method, a complete
Z bounce would take 180 seconds!
Texture mapping for speed enhancements is available as an option on
the 3D Volume pull down and is called Open GL Volume – Texture mapping –
beta. I am still calling this method a beta version since I have not had
enough response with different systems to make sure the software is
functioning properly. The old method of vertex mapping is available via the
Icon in the main menu.
Improvement on straight line displays of
radargrams collected in X, Y, XY, or ANG surveys can also be displayed much
quicker now in Open GL through the texture mapping.
One test I ran
increased the speed by 3.5 times using the new option.
Note texture
mapping is not yet available for topographic warped displays or GPS and
Vector surveys yet.
GPR-SLICE V7.0 www.GPR-SURVEY.com
Multi-Channel advancements and integration
Several new improvements and integration of multi-channel systems
have been incorporated into GPR-SLICE.
3D Radar of Norway has the
GeoScope 31 channel GPR system. Recently, to make their equipment
accessible with GPR-SLICE, 3D Radar provided a new *.vol 3D volume
format.
GPR-SLICE will now read the *.vol data exported from the
GeoScope and extract all these individual radargrams to separate files. This
conversion is done automatically in the Convert Data menu. An example of
the GeoScope imaging in GPR-SLICE is given in Figure 5.
Figure 5. An example of images generated from the 3D Radar GeoScope 31
channel array system. The site is from a Chieftains Hall or Grave site in
Norway (data courtesy of Kevin Barton, EarthSound Associates in Ireland
and 3D Rada in Norway). For more information on this archaeological site
visit http://www.gpr-survey.com/gprslice/clientapplications.html .
GPR-SLICE V7.0 www.GPR-SURVEY.com
For the IDS Stream family of multi-channel systems, various antenna
configurations available are now automatically imported and the information
files generated.
The automatically generated information files
accommodate various configurations currently available with the Stream
products including IDS Stream EM and IDS Stream MT configurations. GPRSLICE will automatically generate the known x and y offsets inside these
multi-channel array systems. The IDS Stream EM for instance has 3 linear
arrays, with the 2 main channel arrays separated by 1.44 m with channel
separation of 12 cm. A 6 cm offset between the 2 main channels is also
currently in this system. Clicking the Import buttons with the IDS Stream
EM identity highlighted, will import all the filenames automatically generate
a infomain.dat and an infochannels.dat files containing all the x, y offsets
(Figure 6). The infomain.dat file will contain the first channel filename which
also has the navigation files associated with it.
The navigation for the GSSI Terravision which is 14 channels has a
hardwired infochannels.dat file made using the channel separation (12cm)
set in the multi-channel box in the Create New Info menu. The Mala Mira
multi-channel system has 16 channels (and a channel separation of 8.6 cm)
is used to automatically generate the infochannels.dat file. The current
available import identities to propagate the information filenames is shown
below:
IDS
IDS
IDS
IDS
IDS
IDS
IDS
IDS
IDS
Gred export
Gred xyz export
Stream X,Y
Stream EM
Stream EM 1-8
Stream EM 9-23
Stream EM 25-39
Stream EM 9-23, 25-39
Stream MT 1-7, 9-14
*.* Radargram identifier
*.vol GPS
*.X.Y,XY
Terravision 14 channel-X,Y,XY
Terravision 14 channel-GPS
Mala Mira 16 channel-X,Y,XY
Mala Mira 16 channel-GPS
IDS Stream MT
IDS Stream MT 8, 15, 16
GPR-SLICE V7.0 www.GPR-SURVEY.com
Figure 6. A new import options for multi-channel systems is available in the
Create New Info menu.
An example of multi-channel imaging with the IDS Stream system was
recently done by Gianfranco Morelli and Alex Novo at the plaza adjacent to
the Leaning Tower of Pisa in Italy (GeoStudi www.geostudiastier.com) .
Images
from
this
survey
can
be
seen
at
http://www.gprsurvey.com/gprslice2/multichannelgpr.html .
The new import option for multi-channel also has imports for Terravision,
3D Radar formats and for Mala Mira multi-channel system. The infomain.dat
and infochannels.dat files are automatically made on import and will
generate the infochannels.dat file based on currently known channel offsets
for these equipment. With the import option, there is no need to explicitly
generate the names of the profiles.
GPR-SLICE V7.0 www.GPR-SURVEY.com
Delete Double GPS Scan #’s – Critical Option for GPS Fallout
A recent GPS dataset that came to me from Lee Harrison at PanAmerican
Consultants (www.panamconsultants.com) was collected under a tree
canopy and was quite noisy. The GPS log file collected with the Sensors and
Software Noggin equipment, reported the trace #, followed by 4-5 or more
of the GPS NMEA string $GPGGA which is the one used in GPR-SLICE for
navigation. Normal operations of the GPS with this equipment will have a
log file of the Trace # followed by 1 line of the $GPGGA. There can be other
NMEA strings, but usually only one $ GPGGA line will follow the Trace #.
However, in the instance with poor GPS and significant fallout, multiple
$GPGGA lines were written to the log file. It is critical that these points be
removed from the converted *.dt1.gps navigation files generated in GPRSLICE. There is a new button called Delete Double Scan#’s (Figure 7)
available in the GPS Track menu.
Figure 7. Location of the new Delete Double Scans operation in the GPS
Track menu.
GPR-SLICE V7.0 www.GPR-SURVEY.com
Miscellaneous improvements

JRC Handy Search Concrete Scanner 12 bit binary format conversion
to 16 bit GPR-SLICE format added

Independent shifting/multiplication
information file editing menu.

Generic extension capture of filenames in user browsed directories in
the Make Info File menu using the Import button

Improvement on initial wobble conversion of radar data with signficiant
low frequency noise.

Compilation of Export-HorzXYZ.dat files with no headers from horizon
detection.

Netplot functionality built into Open GL 2D

Sharpening filter add to Grid Filter menu

\Edit\ folder addition added to all GPR-SLICE projects to preserve
radargram edited radargrams – replacing the work dump folder

Import of all the filenames in a folder in the Create Info File – speeds
up GPS info file generation

Slide-bars for editing RGB import colors in the Color Table menu
of
individual
columns
in
the
Upcoming Events
May 24-28: National Park Service Archaeological Geophysics Workshop. A
half day GPR lecture with a brief introduction to data processing as part of
Steve DeVore’s Archaeological Geophysics workshop will be presented on
Thursday, May 27 at the Knife River Indian Villages National Historic Site in
North Dakota. For more information on attending this week long event
which also includes other Geophysical methods, please contact Steve DeVore
of
the
Midwest
Archaeological
Center,
Lincoln
Nebraska,
[email protected].
GPR-SLICE V7.0 www.GPR-SURVEY.com
June 21: GPR archaeological geophysics workshop at the 13th International
Conference GPR 2010, in Lecce, Italy. Instructors are Dr. Salvatore Piro, Dr.
Brian Damiata, and Dr. Dean Goodman.
http://www.ibam.cnr.it/gpr2010/workshop.htm
June 21-25:
GPR-SLICE/GPRSIM Software Exhibit at the 13th
International Conference on GPR 2010 in Lecce, Italy from June 21-25.
http://www.ibam.cnr.it/gpr2010/exhibitions.htm
Starting this April we began to deliver invoices via email and using our new
accounting software. We hope that this meets with approval of all users in
our attempt to become a paperless office and to be greener!
Best wishes, Dean
GPR-SLICE V7.0 www.GPR-SURVEY.com