Ground Penetrating Radar vs. Exploratory Dig - What's the Difference?

If you're in the process of buying a home, and possibly located an oil tank, you may have heard the terms "ground penetrating radar" (GPR) and "exploratory dig." So, what's the difference between the two? Keep reading to find out!

Example of GPR image of buried UST

How Ground Penetrating Radar Works

Ground penetrating radar is a non-destructive testing (NDT) method that uses electromagnetic waves to create an image of the area being inspected. A GPR machine emits waves that penetrate the ground and bounce back off of objects in the soil. The waves that bounce back are then received by sensors on the GPR machine and converted into an image that can be interpreted by a trained technician.

The main advantage of GPR is that it is nondestructive, meaning that it does not require any excavation or damage to the property being inspected. GPR can be used to inspect both reinforced concrete slabs, driveways and also penetrate soil to obtain images of buried UST's. It can detect a variety of potential problems, including abandoned oil and septic tanks, void spaces, rebar location, and pipe routes.

GPR image of tank lengthwise

Same image in thermal detection mode

Exploratory Dig

An exploratory dig is exactly what it sounds like - digging a hole or trench in order to explore what's beneath the surface. This method is often used to confirm the results of a magnetometer or metal detector. Metal detection is a very important tool in locating underground storage tanks, however it can be inconclusive at times. In this case you need to further examine the area of concern with either GPR or an exploratory dig.

Of course, since this method involves digging, it is destructive and can be quite disruptive (not to mention messy!)


Which method should you use? If you're looking for a non-destructive way to survey an area, GPR is your best bet. However, if you need to further confirm the results of a GPR survey or locate buried utilities that aren't showing up on radar data, an exploratory dig may be necessary. So, which is better—GPR or exploratory digs? The answer depends on your specific needs and situation. If you're looking for a quick and relatively non-invasive way to check for buried utilities and other features, GPR is probably your best bet. Both ground penetrating radar and exploratory digs have their own advantages and disadvantages. Ultimately, the decision of which method to use depends on factors such as the area your surveying and property owners desire to allow destructive digging.

We believe GPR is the best avenue of action in most cases and should be used before invasive procedures. An exploratory dig while very useful at times , should be a last resort and only used after other non-destructive methods fail. A trained professional will be able to recommend the best course of action for your particular situation.

Have questions about GPR and why its used? See our other blog posts on this topic.

GPR image of oil tank under rebar reinforced driveway.
Same image as above in thermal detection mode, highlighting the metal rebar at the surface.

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