ground penetrating radar

What is Ground Penetrating Radar (GPR)?

Ground penetrating radar (GPR) is a technology that allows you to see objects underground. Used for locating utility lines, septic systems, underground storage tanks and voids, old building foundations, and other structures, it is superior to traditional electromagnetic locating in some conditions because it can detect both metallic and non-metallic objects up to 12 feet underground, or even much deeper in some soil conditions.

Numerous hazards lurk underground creating potential for serious accidents, injury to workers, construction delays and unanticipated expense.

It’s vital for utility locators to be able to “see” everything that’s underground. Traditional locating methods may not detect non-metallic and non-conductive objects such as PVC pipes, cables with broken or damaged tracer wires, abandoned utilities, conduits containing asbestos, concrete sewer and stormwater systems, and old burial sites.

GPR scanning is also beneficial in identifying different utilities that are buried close together. It can reliably estimate the depth of utility lines, allowing for better mapping of underground features. It is often used for planning the installation of new utilities.

In addition to identifying subsurface structures, ground penetrating radar can detect soil disturbances such as previous excavation sites and trenches.

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How does GPR scanning Work?

GPR scanning equipment resembles a lawnmower with a digital screen. A site to be scanned with ground penetrating radar is usually marked out in a rectangular grid prior to scanning. The scanner is rolled across the ground perpendicular to the anticipated location of the utility (as indicated on reference maps).

GPR systems direct electromagnetic/ radio waves in the 1 MHz – 1 GHz range down into the earth. Objects underground reflect the waves back to the surface, revealing location information to the scanner. This information is displayed in real time on the screen. Our GPR experts can choose among several different kinds of displays for the screen.

The presence of a utility is indicated by an inverted V, also called a hyperbola, on the screen. Horizontal positions of objects are reflected very accurately.

gpr hyperbola

The depth to the utility can be estimated from the data on the screen. Scanning the site systematically in the grid pattern reveals the alignment of the utility line. Depth slicing can reveal the orientation and depth of different utility lines and the orientation of structures such as vaults. It can also determine the slope of structures such as storm sewers.

GPR scanning is most successful in materials that do not conduct electricity well. For example, sandy soils can be scanned more easily and to greater depth than clay soils. Old concrete slabs are easier to scan than new concrete slabs that contain more moisture.

How Accurate is Ground Penetrating Radar?

GPR scanning is very accurate in identifying the horizontal positions of objects. While ground penetrating radar can determine the presence and location of objects underground, it cannot identify precisely what the object is. Characteristics such as shape and size can help identify what the structure is.

Challenges with GPR

GPR scanning can be difficult on uneven ground surfaces. Also, the radio signals do not penetrate effectively through highly conductive materials such as clay soil.

What GPR equipment does 2M Locating use?

2M Locating uses LMX200 ground penetrating radar scanner by Sensors & Software along with a TopCon external GPS/GNSS for even greater positioning accuracy. This feature allows position displays and image overlays in Google Earth and other geographical information system (GIS) formats. The data gathered can generate 3D depth slices

LMX200 GPR

What information can I get from a GPR scan?

High-resolution images are available immediately of:

  • Screen captures
  • Line data
  • Depth slices
  • Relative positions of multiple utility lines
  • Improperly design new utility routes.

2M Locating can bring these ground penetrating radar findings to life through integrating the data with CAD, Google Earth, GIS, and even 3D and Augmented Reality (AR). 2M Locating will archive your GPR data for future reference.

How Much Does Ground Penetrating Radar (GPR) Cost?

Each project has a number of variables, such as:

  • Type and number of utilities being located
  • The project size
  • Location and our travel costs
  • Complexity or uniqueness of the request
  • Deliverables requested (GPS maps, AutoCAD drawings, building measurements, photographs, etc.)
  • Additional requests

What is Included in the Price?

2M Locating can provide the following services:

  • 811 Coordination (optional, for a fee)
  • Utility locating using EM locating and GPR as appropriate
  • Mapping and documentation using field markings, AutoCAD and GPS/KMZ image overlays (optional, for a fee)
  • Photo records (drone and point of view) (optional, for a fee)

We will take these into consideration when determining a price.

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