Utility locating GPR systems provide developers, builders and contractors with a way to confirm building plans and to locate utilities underground. The system allows users to identify pipes, electrical cables and other ground features ensuring that any work done will be minimally disruptive. These systems can be invaluable for people who are looking to perform major works, especially in older cities where the layout of the building and any utilities may be unpredictable.
It is not uncommon for workmen to deviate massively from the plans when they are expanding or adding services to a property. With older buildings, especially ones that predate strict records, it can be difficult to be confident in what areas can be dug up.
How GPR Works
Utility locating GPR systems work by using waves directed into the ground, and a device that measures the length of time the waves take to ‘bounce back’. Based on knowledge of the type of soil and its density and what is supposed to be under the ground, the system can create images that will highlight areas of denser material (which could be solid bricks or metal), or voids (which could be gaps in the soil, or pipes).
GPR is not perfect. It may not be able to pick up on a pipe full of water, or it may give unusual readings in certain types of soil. It is, however, far more reliable than most alternatives and it is vastly preferred to the idea of just digging lots of holes in the ground.
There are two main ways of using GPR. One is to use a locator device and mark the ground as you go. This is good for small site scans. The other is to collect the results into a computer readout for analysis at a later date. This can be handy for very large sites or where you are not sure what to expect from the scan and you want to be able to get an expert to look at it for you.
The readouts will give you a clear idea of where there are voids or changes in density in the ground, and these can help you to understand the features underground. However, in areas where there may have been older buildings or archaeological sites of interest, or in areas with underground rivers or unusual soil, it may not be as simple as just looking at a blip and knowing it is a sewer or a pipe.
Even so, GPR gives you that initial idea of what to look at, which can be invaluable. The locate and mark technique, especially when combined with metal detection or current detecting systems for metal pipes, can be an effective method of tracing utilities, especially if you know where they start. The technique can tell you where the utilities are, and also roughly how deep they are so that you have some idea of what you can and cannot move safely. This is a good starting point for planning your work.