Is GPR a safe testing technique?
Yes. Ground-Penetrating Radar is extremely safe and emits less than 1% of the power of a cellular phone signal.
Can GPR distinguish between post-tension cables and rebar?
For the vast majority of operators, the answer is NO! Ground-Penetrating Radar alone cannot distinguish between types of subsurface items; that ability is entirely dependent on the skill and knowledge of the operator. As with all skilled trades, a degree of mastery is required to accurately identify sub-surface items. Without the correct training, it may be easy (and costly) to misidentify items.
However, whereas most GPR companies provide their customers with information of embedded items' locations, Structural Radar Imaging makes it a priority to train technicians to go further and identify the types of items, including cables, rebar and conduit.
How deep can radar penetrate?
The signal depth is dependent on the type of material being scanned and the selected radar antenna. For underground utility locating, Structural Radar Imaging technicians typically use a 400MHZ antenna that can penetrate to a depth of seven feet under ideal soil conditions. For concrete scanning, the 1600MHZ antenna may penetrate to a depth of 24 inches under ideal conditions, and our techs are often able to provide a more accurate image by scanning from multiple sides of a structure, if accessible.
Can I see non-metallic subsurface features with GPR?
Ground-Penetrating Radar is extremely accurate when it comes to locating metallic and non-metallic objects. GPR systems work by sending a pulse of energy into the ground from an antenna. An integrated computer records the strength and time required for the return of reflected signals. Any subsurface variations, metallic or non-metallic, will cause signals to bounce back. When this occurs, all detected items are revealed on a computer screen in real-time. Structural Radar Imaging GPR techs can often tell from the signal returned whether the feature in question is metallic or non-metallic.
Can GPR be used on vertical surfaces or on a ceiling?
Yes. We regularly use our equipment to scan for the location of embedded items in columns and walls. On occasion, we may also scan from the underside of a floor to mark out any reinforcing steel, post-tension cables or other embedded conduits that may be difficult to see from the top of the slab or deck, especially when a customer wants to set anchors into a floor for seismic bracing or to hang large piping.
Can GPR determine how deep an object is below the surface?
Yes. If there is another object embedded at a known depth, SRI technicians can provide a very precise depth calculation of other discovered items. If there are no other objects at previously known depths, we can still use Ground-Penetrating Radar to determine depths based on our radar signal. However, it is important to note that moisture hinders the strength of the radar signal, often lessening the depth of penetration, which may in turn affect the accuracy of depth readings.
Is GPR necessary if we need to use the "811 Call Before You Dig" service?
"Call Before You Dig" is a National Utility Notification agency, designed to safeguard our infrastructure of pipes, mains and lines that bring utilities to our communities. (See more at: http://www.callbeforeyoudig.org/)
While each state has its own regulations, local service personnel will often identify previously documented utilities belonging to utility companies. Ground-Penetrating Radar (GPR) becomes valuable when a construction company is concerned with utilities that may not have been well documented, in addition to being able to provide specific depth information.
What is GPR used to determine when scanning pavement?
Ground-Penetrating Radar can measure pavement thickness and reveal other conditions that are not visible from the surface. On concrete, GPR can be used to detect reinforcements, pour breaks and asphalt patches. On bridge decks, we can use the technology to assess delamination and freeze-thaw damage, to compute reinforcement depths, to evaluate deterioratio, to identify the amount and location of overlay unbonding, to measure overlay thickness and to provide quality control for placing reinforcement bar.
Can GPR tell me the size of a void or cavity below ground?
Ground-Penetrating Radar can determine the area or boundaries where a void is present, and at what depth it begins. The radar technology, which relies on returning signals from contact with surface area, cannot determine the overall depth of a void beyond where it begins.
How is the collected data recorded and presented?
Using state-of-the art equipment, our technicians can collect and present data onsite, in real-time. Depending on the surface type and whether it is finished, our technicians may use a variety of writing tools to clearly mark critical items and clear spaces. In fact, it is quite common for concrete contractors to penetrate or core immediately after our technicians have scanned and marked "OK" zones for them to proceed.
Can I use my cell phone around the equipment?
What is the cost of a typical GPR survey?
Cost is determined by the location, time and scope of each project. Structural Radar Imaging offers competitive pricing with a minimum rate for 2.5 hours of scanning, but we may offer a discount depending on the difficulty and time required to complete a job. For an accurate estimate, we recommend calling our scheduling line (253-796-5637) to request a quote specific to your GPR needs.