Ground Penetration Radar (GPR) measures the signal strength of reflected electromagnetic pulses transmitted into the subsurface. A pulse is a travelling disturbance of the electromagnetic field in the sub-surface and is reflected at interfaces between contrasting mediums. As such GPR is often used to identify material changes not visible at surface. GPRplus is a ground scanning device that can image the subsurface at depths of a few metres up to 200 metres. Terravision’s systems can achieve this because they utilise low frequency signals and have a large dynamic range.
Dynamic range is the currency of penetration: the more you have the deeper you can see. Traditional GPR units typically have a dynamic range of c. 96dB, after signal amplification and pre-processing of the received signal.
Furthermore, they often operate at significantly higher centre frequencies meaning that they spend more currency per metre of penetration. GPRplus systems have a dynamic range of c. 126dB and use low frequency signals which results in less cost of energy per metre of penetration and greater spending power then traditional units.
How else is GPRplus™ different?
GPRplus systems have a greater bandwidth than traditional units. The unique transmitters produce signals that have a bandwidth between 0.5 – 1000 MHz, whereas traditional GPR units typically have a bandwidth that is 100% of the given centre frequency i.e. an antenna with a centre frequency of 500 MHz is sampling frequencies between 250 – 750 MHz. This means GPRplus is capable of capturing the same data as traditional GPR units as well as capture responses from a much greater depth.
You might hear about other systems reducing their signal to noise ratio (SNR) through methods such as hyper stacking. While this may achieve results in environments with low ambient background noise, it does not work in areas where the 'noise floor' is high. GPRplus overcomes this challenge by using signals that have a higher strength than most traditional GPR units. This means GPRplus gets results in environments considered too difficult for traditional GPR units.
Customisable GPRplus™ solutions
One of the greatest benefits of GPRplus is that it is not a fixed system. It is made up of a series of interchangeable parts. Terravision is able to select the right parts to put together the best solution for a given problem. The analogy to use, is that traditional GPR units are like wrenches: each system is designed for one particular nut. The problem is, GPR technology is expensive and no one has all the wrench sizes needed for a particular project. Therefore, they make the most of the tool they do have. GPRplus is like an adjustable wrench, it can be adjusted to best fit every nut on site.
Depending on the configuration of the device and the parameters of the subsurface, GPRplus is designed to study the soil subsurface structure to a depth from a few meters to hundreds of meters. GPRplus has a role to play in any sector where humans are interacting with the top 200m+ of the earth’s surface.