Newsletter - July 2015
GPR-SLICE users,
I would like to welcome the following organizations to the GPR-SLICE
community
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Grupo Aralfe, S. de R.L. de C.V., Mexico
Geoinstruments International S.A.C, Peru
Leica, Geospatial Solutions Division, Heerbrugg, Switzerland
Edenbros LLS, Saint James, Missouri
Messiah College, Mechanscsburg, Pennsylvania
Golder Associates Pty Ltd, Australia
School of History, Classics and Archaeology, Newcastle University, UK
GPR Pro, UK
Geomatic Solutions S.L.,Galicia, Spain
Dept of Geosciences, Mansfield University, Pennsylvania
Nanjing Hydraulic Research Institute, Jiangsu Province, China
Dept of Civil Engineering, Chung Hua University, Taipei, Taiwan
Reveal Infrastructure, New Zealand (www.revealinfrastructure.co.nz)
Target Geophysics, Belgium (www.targetgeophysics.com)
Mercian Archaeological Services, Nottingham, UK (www.mercian-as.co.uk)
Korea Polar Research Institute
Sambo GeoTek, Korea (www.geotek.co.kr)
GPRSIM Software licenses were delivered to: Corpo
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Beijing Municipal Engineering Research Institute, China
German Army
IPA Electronik, Turkey
Software Updates
Among the most important or requested improvements added to GPR-SLICE
V7.0 Software are:
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Analytics menu – radargram threshold filtering
ASCII to *.xyza radargram export
Legend customization options
Max/min customization for ABSOLUTE normalization displays
Oasis Montaj *.gxf export
GSSI dual frequency separation
Radargram Threshold
A new menu called Analytics was added under the Filter draw down menu
(Figure 1). The first operation added to this new menu is a Rad Zeroing
button. Often on a radargram display one might only want to show data
above and below certain amplitudes on the pulse. Trying to set this with just
the color transform can be accomplished visually; however the displayed
data are only colorized and not actually changed in the radargram. With this
new threshold option, the user can independently set the negative and
positive threshold below which all recorded radar values will be shown as
zero. The operation will also write the radargram with threshold applied to
the \work\ folder. The filtering operation will set all pulse values less than
the set min/max values to binary 0.
Note: For the Hilbert folder the negative threshold is idle as no negative
values exist from this filtered radargram.
Figure 1.
menu.
Radargram threshold option is available under the Analytics
ASCII to *.xyza radargram export
A new ASCII to XYZA button in the Filter menu was added which will allow
the user to export any processed radargram into a 4 column text version of
any radargram (Figure 2). X and Y are the horizontal position of each
sample value recorded in the radar pulse; the Z value is the depth of pulse
sample based on the time/depth axis chosen in the Options menu. If
nanoseconds is chosen Z will be in nanoseconds – if a depth unit is set then
Z will be converted to that depth unit using the active velocity.
Once the operation is run, the processed folder that was set will have
ASCII files with the extension *.xyza written. These can be easily imported
to any statistical mapping software for further analysis. Currently, users
involved in biomass studies at McMaster University in Canada have
requested this option and require measuring pixel counts of Hilbert
transformed data samples above a certain threshold for their research.
Note: The size of ASCII files are significantly larger than the binary format
used for radargrams so don’t be surprised to see the converted radargram in
*.xyza format being 5-10 times larger on disk.
Figure 2. Radargram export option to 4 column ASCII *.xyza format for
each radargram was added to the Filter menu.
Customizable legend display
Color legends in the 2D Pixel Map menu can now be customized to display
labels at any desired frequency.
In addition, horizontal (Figure 3) or
vertical displays of the legend can be set. The legend size is maxed out to
512 pixels or shorter depending on the axis size that the legend is output to.
The number of decimals for labeling can also be adjusted. As all 2D grid
data are now recorded as double precision floating point numbers and not
strictly integers, all grid maps have decimal data included. For time slice
images where the squared amplitude is being used, the numbers are quite
large and the display of decimals data is insignificant and can be set to 0.
For imported – non GPR data – the decimal data can be shown with decimals
if the data necessitate this resolution.
Figure 3. Customizable legend displays for 2D time slices displays are
available under the Options menu.
Note: For users that prefer displays within the original radargram binary
recording, the time slice parameter in the Slice/Resample menu can be
changed to abs(amplitude) for example. This will constrain the colorization
and the labeling to +/- 32768 for 16 bit radargrams. For squared amplitude
the numbers can be quite large and as big as +/- 32768^2.
For 32 bit
radargrams we currently only allow abs(amplitude) time slice cut parameters
as 64 bit numbers to describe the reflected radar field are highly
unnecessary for our terrestrial applications!
Also remember that
colorization of all graphic displays is constrained to 256 colors or
equivalently 8 bits of resolutions in the data!
ABSOLUTE normalization customizable settings
The displays of time slices for ABSOLUTE normalization now have
customizable inputs for the minimum and the maximum values (Figure 4).
ABSOLUTE normalization will set the peak value and the minimum value
across an entire set of time slices and colorize the data based on the values.
Lower case absolute normalization – where the minimum and maximum
between all the time slices displayed is searched first prior to display - is the
same as upper case ABSOLUTE normalization display if the user set values
are identical. The customization here is to allow users investigating 4-D
measurements of GPR to “re-colorize” data collected and to investigate
changes in the signal over time. To do this requires fixing the minimum and
maximum values before colorization.
Note1: For those using the Grid Blocking function for either the Multichannel
menus or the Grid menu, when displaying multiple blocks at the same level
in the Pixel Map menu, ABSOLUTE or absolute normalization should be used.
This will insure that all the blocks are colorized with reference to one set of
min/max values – whereas on relative normalization each map is
independently normalized and could cause mosaic changes between blocks
when looking at the data as a whole.
Note2: In the example in Figure 4 the absolute minimum and maximum
were set to the maximum squared amplitude time slice parameter of
32768^2 = 1073741842 which is the largest possible time slice value that
can exist in a grid map. This value is unlikely and can only come in the
case of an area that has a completely strong reflection.
However,
overgaining of a radargram, creating clipped regions could possible create a
time slice parameter in grid map with this value.
Figure 4. ABSOLUTE normalization displays on time slices now can read a
user set min/max for controlling the colorizations.
GeoSoft Oasis Montaj *.gxf export format
A new export format for import of GPR-SLICE 2D *.grd grid files has been
created for import into Geosoft’s Oasis Montaj Software. In the Grid menu
there is a listbox for choosing different formats including the first export
option for making Surfer grids (Figure 5).
The *.gxf (Grid Exchange
Format) is an ASCII format that can be directly imported into Oasis Montaj
Software. The *.gxf format was in fact developed by GeoSoft for sharing
grid files with other software. The exported grid files are written to the \grd\
folder. An example of a grid file in GPR-SLICE and its counterpart *.gxf
format displayed in Oasis Montaj viewer is shown in Figure 5.
Figure 5. GPR-SLICE now has *.gxf (Grid Exchange Format) 2D grid files
conversion for import to GeoSoft’ Oasis Montaj Software.
GSSI dual frequency equipment channel separation
The GSSI dual frequency channels is now moved from the convert menus
to the Edit Info File menu. The separation will place the high and low
frequency channels directly into the \raw\ folder rather than the \radar\
folder. This was done to allow additional pre-conditioning of the radargrams
to remove low frequency drift – wobble – in the pulses. Shown in Figure 6 is
the new location of channel separation for GSSI DF equipment. Several of
the DF radargrams are shown to have significant drift, indicating that
bandpass filtering in the recording is not completely active in the new
recording unit. In any event, this noise can be easily dealt with during
conversion of these radargrams as the data are now placed in the \raw\
folder during the separation process and bath gain + wobble conversion can
be implemented.
Figure 6. Example of a GSSI dual frequency radargram showing significant
0 drift noise that can be removed during conversion using batch gain –
wobble operations.
Other features and options added to GPR-SLICE include:
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Bi-linear inter-grid interpolation algorithm used in display of OpenGL radargrams with
topographic adjustment allowing for smooth topo displays in the event of low resolution
topography grids .
Justin Klein's Radar2dScroller.exe now supports 32 bit radargrams – launched via
OpenGL 2D Radar menu pulldown.
All 2D grid files generated for GPR or imported data are now written as double precision
floating point - replacing integer only grid files.
Peak hyperbola response output files in dB provided on compilation in Search menu.
Programming unification of most 16 bit formats into a single menu covering different
equipment.
GPR point moving and deletion using mouse operations available in the GPS track
menu.
With lighting engaged, horizon surfaces and topographic surfaces have shading
capabilities in OpenGL Volume.
OpenGL 2D menu shading control adjustment with surface normal array smoothing
prior to rendering.
ASCII GPR convert menu improvement with import customization reads.
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Ang, X, Y, XY to Vector button automatically creates a new information file with the -v
append identifier.
Delete every Nth file button added to the Edit Info File menu added for quick removal of
multichannel files in the information list.
2D *.grd interpolated grid files conversion button to xyz ASCII *.asc files added to the
Pixel Map menu.
Drawn object depth labeling option added to DXF export in OpenGL Volume Draw menu
Direct import of 3 column HSW or RGB 256 color files into the Color Editing menu under
Options.
GSSI dzg extension total station navigation added to Edit Info File menu.
3D binary volume reconfigured from XYZ to XZY - useful for import of 2d geophysical
data such as resistivity profiles which are gridded and interpolated - and then to change
the y axis to z in the made volume.
In addition, binary code reads have been updated and improved in GPRSLICE and have had a significant impact on speeds of various radargram
filtering operations and well binary volume operations since a recent June 24
version was placed on the website. Recent comparisons with the new binary
code readings, migration processing times have nearly doubled in the Filter
menu. For large multichannel pulse volumes, the gap interpolation process
has also nearly doubled in speed!
Upcoming Events
July 8-10: GPR-SLICE Software Exhibit – Near Surface Asia Pacific
Conference, Hilton Waikoloa Village, Hawaii
December 13-18: GPR-SLICE Software Exhibit – American Geophysical
Union, Marcone Convention Center, San Francisco
Recently, we began placing answers to support questions that will be
useful to the entire GPR-SLICE community on our Facebook page. If you
have not yet joined the GPR-SLICE facebook page I would encourage you to
do so. https://www.facebook.com/groups/gpr.slice/
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Dean Goodman
Geophysicist, Phd
GPR-SLICE Software
Geophysical Archaeometry Laboratory
*This newsletters is available in *.doc form on the Subscribers Only page of the
website