This guide explains how to import topographic data (e.g. from LiDAR, total station, or GPS) that was collected separately to your GPR data and then use that data to perform topographic corrections of GPR radargrams in GPR-SLICE.
The guide assumes you have already processed your GPR data and just need to perform the topographic corrections. If you have not reached this point and need help getting started, please refer to the GPR-SLICE training videos.
This can be achieved by following these steps:
Export your topographic data into a comma-delimited XYZ CSV file. This is a three-column file, with eastings, northings, and elevation readings in each row.
Name this topographic data file “Topography.dat” (ensure you have a capital T at the start), and save it inside your GPR-SLICE project folder, within the \dat\ folder.
In GPR-SLICE, first ensure you have done a hyperbola search in the Filter menu in order to create an appropriate velocity model. You will also need to have done any filtering you desire before proceeding with topographic corrections.
Open the static menu, and choose Topography (or static-topography).
Choose your GPR data input folder from the options on the far left, and then click the “Import \dat\Topography.dat” button on the right.
Click OK on the message that appears.
Click on the “GridTopo1.dat” button, which is immediately beneath the “Import \dat\Topography.dat” button used a moment ago.
On the gridding menu that appears, ensure the Xstart, Xend, Ystart, and Yend values encompass the GPR data (i.e. the extent of your topo data gridding needs to be larger than the extent of your GPR data grids). Click the grid button to actually perform the topo gridding. Close this menu and get back to the static topography menu.
If you are just displaying your topographically-corrected radargrams in the OpenGL 3D environment, that’s all you need to do. You can then go to the OpenGL + topo warp screen for displaying the topographically-corrected radargrams.
However, if you need to create topographically-corrected radargrams for further processing or e.g. for drawing horizons on, you will then need to do the following:
On the topo menu, you will need to enter a larger value for the “New Samples/scan” in the lower-left corner. The exact value you need will vary from site to site depending on the total topographic relief present at the site. The aim is to tell GPR-SLICE to create radargrams that are deep enough to encompass all GPR data, once topographic corrections are applied. Side note: in the following steps, you may see the lower edges of radargrams being cut-off. This means that the New samples/scan value you used was too low. If that happens, just return here, enter a larger number, and continue with the following steps again…
Click the “create infotopo” button in the lower-left corner.
Click the “Extract Topo” button. This button takes the topographic data from the topography grid file (created in step 8, above) and extracts the topographic data required for each radar line, based on the GPR’s GPS data log.
Click the “Correct” button, immediately below the “Extract Topo” button.
A new window will open. Click the “import topo” button at the top of the screen to load and plot the topographic data.
You may wish to apply topographic smoothing. This is explained on page 292 of the 2017 version of the GPR-SLICE user manual.
Click the “Batch Topo Cor.” button to apply the topographic corrections to the radar data. This will create new radargram files in the \topo\ folder of your GPR-SLICE project directory. You may have noticed while topographic corrections were being performed that the bottoms of radargrams were being cut-off on the display. If so, return to step 11 and enter a larger “New Samples/scan” value. If not, then continue to the next step.
Close all windows except the main GPR-SLICE window.
Open the edit info file menu, and choose infotopo.dat from the info file selection menu. Close the edit info menu.
In whatever step you need to do next, ensure you use the \topo\ data as the input directory.
These operations are also explained on pages 287-292 of the 2017 GPR-SLICE user manual. This manual can be downloaded here.
This video explains how GPR-SLICE updates are installed. Please note that the method described in this video is only applicable to Hunter Geophysics customers; if you purchased GPR-SLICE from another source, you will need to contact your supplier directly for updates.
Hunter Geophysics is currently developing the iOnTheSky aurora-monitoring camera network. Each camera in the network automatically takes a photograph every five minutes and allows Aurora Australis photographers to see what the Aurora Australis, light pollution, and weather conditions are like at any given moment.
There are currently five cameras installed throughout Tasmania (although one was offline for maintenance on the 31st August). We eventually hope to install dozens of cameras around the world. The footage from these cameras will be made available to the general public via iPhone and Android apps, which will hopefully be released in late 2017.
The below video shows the camera footage from the four operational cameras from 10am 31st August 2017 to 10am 1st September 2017 (from 00:00 to 23:55 on the 31st August 2017, UTC).
The four cameras are situated in Barrington (north Tasmania), Campbell Town (mid-northeast Tasmania), Bothwell (central Tasmania), and Ranelagh (southwest of Hobart, southern Tasmania). The fifth camera (which was offline that day) is based in Abels Bay (slightly further southeast from Ranelagh).
Some GPR manufacturers produce radargram files with identical filenames across different projects or survey grids. Some users like to process multiple projects or survey grids in the one GPR-SLICE project. This means there will be conflicts due to identical filenames. This video explains how to get around this problem.
This video goes for 2.5hrs and should be the first thing ANY new GPR-SLICE user watches. It introduces almost everything you need to know in order to get started with GPR-SLICE.
This video assumes you are using either GPS or robotic total station navigation for your GPR data. If you aren’t using these methods, please consult the user manual (available via your user Dropbox folder; the first few minutes of the below video shows where to find the user manual), or contact us for face-to-face training via Skype (which is included in the price of your GPR-SLICE licence).
After watching this video, we strongly recommend you check out the following tutorial videos:
Hyperbola detection in GPR-SLICE (this requires the BridgeDeck module for GPR-SLICE and allows semi-automatic detection of hyperbolic reflectors in radargrams, which is useful for those doing ground-penetrating radar surveys on concrete slabs in order to map re-enforcing bars (“reo”)).
A full list of all GPR-SLICE training videos is available here.
This video is a few years old; the installation and update processes shown in the video are no longer correct. The rest of the video is correct, though.You will receive an email explaining how to install GPR-SLICE when you purchase the software (or a demo licence). To update GPR-SLICE, please watch the “How to update GPR-SLICE” training video.
If you use anti-virus software, you may have troubles opening or updating GPR-SLICE. We have observed problems with AVG Anti-Virus, Kaspersky Anti-Virus, and BitDefender. You will need to add the C:\slice\v7.0\gprslicev7.exe file and/or the entire directory at C:\slice\ into your anti-virus software’s white-list to override the anti-virus software.