Newsletter - February 2015

GPR-SLICE users, 

I would like to welcome the following organizations to the GPR-SLICE community 

Dept of Archaeology, La Trobe University, Melbourne, Australia Korean Expressway Corporation Tomb Geophysics, Woodbridge, Virginia

(www.tombgeophysics.com) Parsons Overseas (P) Limited, India Quality Services Inc, Rapid City, South Dakota National Forensic Service, Korea Center for Advanced Spatial Technologies, University of Arkansas Daeil Enc, Korea Dept of Geology, University of Utah Murphy Surveys, United Kingdom

In addition, The Southeast Archaeological Research Center in Florida took out a 3rd license, the Dept of Anthropology University of Georgia Athens and the University of Northern Colorado acquired 2nd licenses. GPRSIM Software users have been growing and recently licenses were delivered to: Corpo

1.

Parsons Overseas (P) Limited, India Gradar Geofysik, Italy-Sweden Beijing Tie Jian Project Supervision Co., Ltd., China Dept of Structures and Materials, IWHR BEIJING IWHR-KHL Co., Ltd,

China Wehrtechnische Dienststelle für Schutz und Sondertechnik

Oberjettenberg, Germany Beijing Constructional Engineering Institute, China

Software Updates

Among the most important improvements added to GPR-SLICE V7.0 Software are:

OpenGL 2D XYZ split screen displays complimented with radargram folders

32 bit radargram processing Roll/pitch/yaw added to direct compilation of multichannel data to 3D

radargram volumes Line object conversion in OpenGl Volume Draw to pipes Auto hyperbola detection with a 5 point vertical search help button Negative/opposite isosurfaces Customized trajectory animations Radargram differencing

OpenGL 2D XYZ split screen displays complimented with radargram folders

The OpenGL 2D-XYZ menu will now display the closest radargram when a Zscan anomaly is clicked on (Figure 1). If the nearest radargram found is an X profile, it will display it directly above the Zscan slice; a Y radargram will appear to right side of the Zscan. The compliment slices from the volume are shown in the left and on the bottom of the Zscan slice. Any radargram folder can be highlighted to use for this split screen action. In the example shown, a 3D volume (made from made from migrated/Hilbert transformed radargrams processed with the BlueBox Batch XY decoupled gridding + RSP) is shown, along with raw unprocessed radargrams. A style choice radio button option “style-a+r” or style-b+r” is available to show y radargrams sideways – perpendicular or parallel to the volume slice direction should this be desired. The radargram split screen can be shut off completely with just the “style-a” or “style-b” setting. GPS radargram are not available for this split-screen functionality in OpenGL but are still available in the Pixel Map 2D menu. (In Figure 1, either the x or y radargrams will be displayed but not both at the same time).

Figure 1. The OpenGL Volume XYZ-2D Draw menu with new capabilities to show the nearest XY radargram on Zscan anomaly picking.

32 bit radargram processing

GSSI, Mala and UTSI electronics have recently released 32 bit recording in their newer GPR control units. The Mala GX system, the GSSI SIR4000, and the UTSI Ground Vue GPR Systems all employ 32 bit recording. For those not sure what this entails, this means that the radar pulses are digitized from +/- 2^31 or +/- 2,147,483,648. GPR-SLICE now provides full 32 bit processing in all the menus. An example of the new menu for conversion of Mala 32 bit radargrams is shown in Figure 2. The convert menu 32 to 32 bit is chosen if full 32 bit processing is desired. Conversion down to 16 bit is also available in the menu using the 32 to 16 bit button. The native recording for 32 bit radargrams in GPR-SLICE is signed binary (whereas 16 bit recordings and older 8 bit are unsigned).

Note: For 32 bit binary radargrams, squared amplitude time slices are currently reset to abs(amplitude) time slices in the SLICE/RESAMPLE menu to avoid having to have 64 bit numbers in the ASCII time slice files. To achieve squared amplitude looks, the user can use the “square” transform in the Transform menu to achieve a nearly identical look in the time slice displays.

Figure 2. Full 32 bit radargram conversion and processing is now available for Mala, GSSI and UTSI electronics GPR systems that support this recording capability.

Roll/Pitch/Yaw compensation included in generating 3D volumes (for multichannel licenses)

In the future, roll, pitch and yaw measurements may start to become standard field procedures for some surveys where extra precision is needed for example in utility mapping. There are currently no standards on the recording formats as the manufacturers have yet to incorporate these measurements into their control units and to monitor the orientation/attitude of the surveying antenna. Several organizations are independently recording these values externally and need to include these measurements in the analysis. Recently, a flexible import operation of roll, pitch and yaw were modified and generalized to read either individual files associated with each recorded radargram, or to read a single global file (Figure 3). For surveys with specified individual files for each recorded radargram, the GPS Get Yaw button has flexible reading of a comma delimited file specifying the

roll/pitch/yaw columns to be imported. For surveys where just a single – global roll/pitch/yaw file is recorded, the NMEA time is searched in this global file and the bordering NMEA time in the *.*.gps files is compared and appropriate interpolation between these times is used in the import. Flexible degree or radian import can be used to import the external custom file.

Figure 3. Screen shot showing the new flexible import format for roll/pitch/yaw measurements which can be applied to 3D volumes for multichannel licenses or for vector radargram displays for standard licenses in OpenGL Volume.

In this example a single global file inclusive of the entire NMEA time span and with roll/pitch/yaw is converted to the normalized vector and placed into columns 9, 10 and 11 of the *.*.gps navigation files made in GPR-SLICE. The definition used in the conversion of roll/pitch/yaw angles to the normalized vector is by coordinate transformations:

sy = SIN(yaw(j)) cy = COS(yaw(j))

sr = SIN(roll(j)) cr = COS(roll(j))

sp = SIN(pitch(j)) cp = COS(pitch(j))

rotation around x-axis:

qy=0 qz=1 yy= qy*cr - qz*sr zz= qz*cr + qy*sr

rotation around y-axis:

qz=zz qx=0 zz= qz*cp - qx*sp xx= qx*cp + qz*sp

rotation around z-axis:

qx=xx qy=yy xx= qx*cy - qy*sy yy= qy*cy + qx*sy

xvec=xx yvec=yy zvec=zz

To correct for the roll/pitch/yaw in compilation of 3D volumes (for multichannel datasets), the “vector” survey definition for the information file must be active.

Quick conversion of line objects to pipes for quick drawing

For drawing pipes in 3d can be time consuming to connect all the sections as the rotate and tilt keys need to be used. To help speed up the process, the user can draw the pipes quickly as a continuous line function in 3D, and then press the new L to P (line to pipe) button (Figure 4). The operation will read the current radius set in the OpenGL Draw menu and apply this to the current drawn pipe section. Before the button is pressed, the Section button will need to be toggled to get to the first desired drawn line section to apply the conversion.

Figure 4. Location of the quick button L_to_P in the OpenGL Volume Draw menu which converts line functions to a pipe functions. The desired radius should be set before running this operation.

Auto hyperbola detection with a 5 point vertical search help button

To extend options for searching hyperbola for bridgedeck licenses, a vertical search of 5 points at the apex of the hyperbola is provided (Figure 5). The Help_5pt_Vert button will take 5 points along the vertical axis of the hyperbola. The delta distance between the 5 points is decided by the hyperbola width. After the mouse is clicked on top of the hyperbola (after clicking the Help_5pt _Vert button) the software will take the 5 points and amplitudes and place them into the slots in the menu. The dx values are all 0 and indicates that a single scan is being search in vertical; the dy values shown are the number of samples in the vertical that are to be assigned for the search along the pulse; the amplitudes at the 5 points have been automatically reduced from the actual values at those chosen locations so that thresholds below those found are searched. The user can also manually adjust any of the dx, dy and amplitudes to make a more customized search in case the set searches do not perform well. This may require some trial and error to get the best detection performance.

Figure 5. The Help_5pt_Vert button in the Hyperbola Search menu will automatically set search parameters for threshold detection along the vertical scan at a hyperbola apex.

Negative/opposite isosurfaces

Isosurface displays in GPR-SLICE have typically been used to render the 3D surface of the strongest amplitude thresholds in a volume. Sometimes, the low amplitude surface has more pertinent subsurface information that is needed than just the strong amplitude portion. For this reason, the isosurface displays have been extended to render the weak reflection portion of the volume. To implement this option, a negative value for the isosurface percent threshold in the OpenGL Volume menu can be set (Figure 6). An example for the Nutubaru burial mound is shown. A weak circular reflection is seen which represents a subsurface moat. The moat reflections are weak at this level since the radar waves have not yet encountered the bottom of the moat and are just transmitting through the homogenous soil fill within the moat. Using a negative isosurface, the weak – blue portion of the volume and the moat can be illuminated. In this example, the top portion and surface reflection in the volume are removed by setting the top time z level at 15ns to remove all reflections to this level (see upper left hand menu slot items in the OpenGL Volume screen shot).

Figure 6. Negative isolevels can now be used to render the low amplitude side surfaces in OpenGL Volume.

Customized trajectory animations

Trajectory animations can be customized by launching the new set menu in OpenGL Volume (Figure 7). The start and end angles over the z, x and y axis can be individually set. In addition the angle step in degrees to output the jpg frames in the animation and the number of junctures can be manually set. For a very fine animation a small angle step can be used. The lowest value is 1 degree. The junctures option tells the animation sequence how many times to divide the rotations along each. For instance, if the juncture is set to 1 then the animation will start by rotation the volume display from the z start angle to halfway, then the x axis rotation by half, followed by the y axis rotation if this set. Then, after the y axis rotation is halfway finished, the z axis rotation will finish, followed by the other axis. The order is z, x and y axis rotation in the animation. Default settings are

used if the Set menu is not launched prior to running the trajectory animation.

Figure 7. Customized trajectory animation menu can be launched in OpenGL Volume.

Radargram differencing

The radargram differencing option in GPR-SLICE has been improved to look at any two folders, which can be processed or raw (\radar) folders to compute the difference between radargrams. The input directory folder and the list of folders next to the Rad1-Rad2 button should be selected before running the operation. Radargram differencing is useful to see just the noise content that is being removed from the chosen filtering process. The output from radargram differencing is written to the \work\ folder. Radargram is also an important operation to examine 4D measurements over the same profile. An example of differencing a raw radargram with a background filtered radargram is shown in Figure 8.

Figure 8. Radargram differencing now has options to examine user set folders in the Filter menu. The differenced radargram is written to the \work\ folder.

Other features and options added to GPR-SLICE include:

All convert menus added with z+/- graphic scaling on the vertical axis

SEG2 formats combined under a single SEGY equipment and conversion menu

Time slice + radar2D + OpenGL volume split screen option Background median filter added to RSP batch menu

Upcoming Events

  A 2 day GPR-SLICE workshop is scheduled for February 11-12, 2015. The workshop will closely follow the Advanced Users Notebook with several additions and will include project folders covering:

GPR/GPS imaging folders for all the major manufacturers Signal processing Image processing Ons offset radargram editing

Concrete imaging Historic cemetery imaging Open GL operations Automatic topographic corrections (regular surveys and GPS) Horizon imaging and layer detection (road layer imaging) Vector imaging (tunnel imaging) Auto-hyperbola detection and amplitude mapping (bridgedeck imaging

The workshop is limited to 15 and there are currently 5 slots still available. Please reserve your spaceif you have an interest for additional training.

Recently, we began placing answers to support questions that will be useful to the entire GPR-SLICE community on our Facebook page. The Facebook page can serve as a valuable forum for software users. 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/

_________________________________Dean GoodmanGeophysicist, PhdGPR-SLICE SoftwareGeophysical Archaeometry Laboratory20014 Gypsy LnWoodland Hills, California, 91364  USA818-716-6957    818-434-9932 cellgal_usa_goodman@msn.comdean@gpr-survey.comwww.GPR-SURVEY.com

*This newsletters is available in *.doc form on the Subscribers Only page of the website