The basic components of a GPR system

Ground Penetrating Radar equipment is usually modular and generally comprises two main components:

A control unit, usually with a rechargeable battery to power the system. An antenna, comprising a transmitter and receiver to transmit and receive the reflected signal pulse.

Compact all-in-one systems are also available; however, as they are fixed, they cannot be modified to suit different types of surveys.

For a successful GPR site survey, we firmly believe that the survey must be conducted by a suitably trained and experienced surveyor using the most appropriate GPR equipment available.

The core of our equipment pool that we use daily includes, but is not limited to, the following:

GPR Control units

The control unit contains the electronics that generate and control the GPR pulse of electromagnetic energy waves that the system’s antenna sends into the sub-surface.

The control unit also includes an in-built computer, although some systems use an external laptop. This saves the GPR data generated by the antenna’s receiver on a hard drive or solid-state memory.

Most control units include an integral display unit, which enables a visual means of configuring the system for the survey. It also displays the GPR data in real-time, enabling preliminary interpretation on-site. This helps to ensure that the survey objectives are being met. More detailed analysis is undertaken off-site by uploading the saved data files and using specialist software to process and interpret the data.

GSSI SIR 4000 control unit

The GSSI SIR 4000 control unit

The SIR4000 is a GPR data acquisition system and control unit from GSSI designed to operate with analogue and digital antennas, including the latest dual frequency antennas. Other improvements over the SIR3000, which it replaces, include advanced display modes and filtering capabilities for ‘in the field’ processing and imaging.

GSSI SIR 3000 control unit

The GSSI SIR 3000 control unit

The SIR-3000 is a small, lightweight control unit compatible with all GSSI antennas and offers a flexible option for multi-application users.

  • Lightweight and portable
  • Rugged and weather-resistant construction
  • Windows-based user interface
  • High-resolution colour screen
  • Use handheld or mounted on a cart
  • Removable, rechargeable batteries
  • Compatible with all GSSI antennas
  • GPS integration
  • Internal data storage and removable compact flash card memory

GSSI SIR 30 multi-channel control unit

The GSSI SIR 30 control unit

The SIR-30 from GSSI is a multi-channel GPR system offering a number of advantages over single-channel systems such as the SIR-3000. As the name suggests, multi-channel allows several antennas to be used simultaneously; in the case of the SIR-30, up to 4 (although you can piggyback two units, giving a total of 8 channels). The SIR-30 also offers real-time data processing, including migration, surface positioning, signal floor tracking and adaptive background removal.

It is ideal for high-speed data collection to measure pavement layer thickness, detect cavities, assess airport runways, detect fouled/clean ballast, and detect utilities.

GPR antennas

The antenna is the system’s second key Ground Penetrating Radar equipment component. It comprises a transmitter and receiver. The receiver sends the GPR signal from the control unit into the subsurface as a series of pulses. Changes and features within the subsurface produce reflections. The receiver receives these reflections, together with amplitude information and time-travel information. The data is sent back to the control unit, where it is saved electronically and, for most systems, displayed on an integral screen.

GPR scans can be undertaken using antennas with different central frequencies. The resolution and detail of GPR data increase with higher antenna frequencies; however, the depth of penetration decreases. As a general rule, it is desirable to use the highest frequency possible while still meeting the objectives of the survey. When undertaking site surveys, we carry a range of antennas that may be suitable for the conditions likely to be encountered. This enables us to select the most suitable antenna for the survey. We often scan using multiple frequencies to ensure the best possible data is recorded.

GSSI 2600 MHz high-resolution antenna

The GSSI 2600 MHz high-resolution antenna

The 2600 MHz antenna is an ultra-high resolution antenna suitable for inspecting concrete structures, the location of embedded rebar, post-tension cables and conduits.

Specification

  • Centre Frequency: 2600 MHz
  • Depth Range: 0-0.4 m (0-12 in)
  • Weight: 1.8 kg (4 lbs)
  • Dimensions: 38x10x165 mm (1.5x4x6.5 in)
  • Model 52600S
  • Manufactured by: GSSI

Uses

Typical applications for the 2.6 GHz antennae include:

  • Concrete floor slab surveys
  • Locating services and conduits in concrete slabs
  • Locating Tendon Ducts in Post-Tensioned Concrete
  • Locating underfloor heating pipes
  • On-site rebar location and mark-up surveys
  • Rebar mapping and concrete imaging
  • Void location in construction and below slabs

GSSI 2000 MHz palm antenna

The GSSI 2000 MHz palm antenna

The Palm Antenna is the most compact GSSI antenna available to date. It measures only 104.5×91.5 x 154.7 mm, enabling it to be used in tight and confined spaces. It is particularly good at scanning into corners, against walls and around obstructions (it can scan to within 45 mm of an obstruction).

The antenna includes a dedicated survey wheel (located to the rear of the antenna, a replaceable skid plate, and a removable handle to reduce antenna height, if necessary.

Specification

  • Centre Frequency: 2000 MHz
  • Penetration Depth: up to 400 mm
  • Uses: rebar location/mapping and concrete investigation
  • Manufactured by: GSSI

Uses

On-site, the main benefit of this antenna over others of a similar frequency is its compact size. This makes it very useful for scanning areas where access is restricted or obstructions, such as pipes, ornate mouldings, etc., are present. Typical applications for the GSSI 2000 MHz Palm antennae include:

  • Locating embedded metal in masonry
  • Locating Tendon Ducts in Post-Tensioned Concrete
  • On-site rebar location and mark-up surveys
  • Rebar mapping and concrete imaging

GSSI 1600 MHz antenna

The GSSI 1600 MHz antenna

The 1600 MHz antenna is a high-resolution, all-purpose antenna suitable for inspecting concrete structures and locating/mapping rebar, post-tensioned tendons, and conduits. It is typically used for general investigation works, including floor slabs, walls, bridge decks, and shallow void detection.

Specification

  • Centre Frequency: 1600 MHz
  • Penetration Depth: up to 500 mm (in concrete)
  • Uses: Rebar location/mapping, concrete investigation and shallow void detection
  • Manufactured by: GSSI

Uses

Typical applications for the 600 MHz antennae include:

  • Chimney flue location
  • Concrete floor slab surveys
  • Locating services and conduits in concrete slabs
  • Locating embedded metal in masonry
  • Locating Tendon Ducts in Post-Tensioned Concrete
  • Locating underfloor heating pipes
  • On-site rebar location and mark-up surveys
  • Rebar mapping and concrete imaging
  • Retaining wall surveys
  • Void location in construction and below slabs
  • Wall and slab thickness measurement

GSSI 900 MHz antenna

The GSSI 900 MHz antenna

The 900 MHz antenna is suitable for numerous applications requiring shallow penetration down to 0.9 m, including void detection, concrete/construction thickness measurement and shallow utility location. It can also be used for the location of deeper rebar.

Specification

  • Centre Frequency: 900 MHz
  • Penetration Depth: up to 900 mm
  • Uses: deeper rebar location/mapping, void detection, shallow utility
  • Manufactured by: GSSI

Uses

Typical applications for the 900 MHz antennae include:

  • Chimney flue location
  • Locating embedded metal in masonry
  • Retaining wall surveys
  • Void location in construction and below slabs
  • Wall and slab thickness measurement
  • Railway ballast thickness and evaluation

GSSI 400 MHz antenna

The GSSI 400 MHz antenna

The 400 MHz antenna is most commonly used for detecting and mapping utilities, as well as shallow engineering and environmental applications.

Specification

  • Centre Frequency: 400 MHz
  • Penetration Depth: up to 2m
  • Uses: Utility, engineering, environmental, void detection
  • Manufactured by: GSSI

Uses

Typical applications for the 400 MHz antennae include:

  • Retaining wall surveys
  • Void location in construction and below slabs
  • Wall and slab thickness measurement
  • Railway ballast thickness and evaluation

GSSI 300/800 MHz dual-frequency antenna

The GSSI 300/800 MHz dual-frequency antenna

The 300/800 MHz dual-frequency (DF) antenna records two sets of data (one for each antenna frequency), enabling shallow and deeper targets to be detected at optimum resolution. The resolution and detail of GPR scan data decrease with lower antenna frequencies; it is, therefore, desirable to use the highest frequency possible while still meeting the survey objectives. The data can be merged using Radan software to display both sets of data in a merged file, making data analysis and interpretation easier and more efficient.

Specification

  • Centre Frequencies: 300 and 800 MHz
  • Penetration Depth: up to 4m
  • Uses: utility surveys, archaeology, deep construction detail
  • Manufactured by: GSSI

Uses

Typical applications for the 300/800 MHz dual-frequency antenna include:

  • Retaining wall surveys
  • Void location in construction and below slabs
  • Wall and slab thickness measurement
  • Railway ballast thickness and evaluation

GSSI 270 MHz antenna

The GSSI 270 MHz antenna

The 270 MHz is suitable for the detection and mapping of deeper utilities, as well as shallow engineering and environmental applications.

Specification

  • Centre Frequency: 270 MHz
  • Penetration Depth: up to 6m
  • Uses: Utility, engineering, geotechnical
  • Manufactured by: GSSI

All-in-one GPR systems

There is an increasing number of all-in-one GPR systems available. These typically house the control unit, antenna and power supply all in one unit. Because the component parts are all fixed, the main advantage of these systems is that they are mostly pre-configured and, hence, simple to use. They are, however, also very limiting. As the component parts are fixed, they lack versatility, and components can’t be interchanged to suit site and survey conditions. For this reason, they tend to be one-trick ponies and are designed for a specific survey type.

GSSI UtilityScan DF

The GSSI UtilityScan DF

The GSSI UtilityScan DF is a dual-frequency GPR system designed for utility location. It features a digital dual-frequency antenna (300 and 800 MHz), allowing shallow and deep targets to be detected simultaneously with a single pass of the antenna. This reduces time on site whilst at the same time improving utility detection rate.

Data Display

The UtilityScan DF has several modes to view the data in real-time during data collection:

  • Split View – allows the two channels to be viewed simultaneously, aligned one above the other.
  • Blend Mode: This displays a multi-frequency data fusion in real-time, combining the high-resolution near-surface data (800 MHz) with the lower depth detail (300 MHz) in a single view

Flexibility

Although the UtilityScan DF is primarily designed for utility surveys, we are finding it useful for other GPR surveys, such as:

  • Detection of underground obstructions
  • Locating underground voids, especially under concrete or asphalt pavements
  • Burial sites
  • Geological investigation
  • Archaeology

GSSI StructureScan Mini 3D

The GSSI StructureScan Mini 3D

The StructureScan Mini is an all-in-one GPR system for concrete inspection. With a 1.5 GHz antenna, this handheld system is useful for rebar detection to depths of up to 400 mm. Integral software on the 3D model provides a plan view of reinforcement (an x-ray-like image). Our unit is mainly used by our Building Inspection department for rebar detection prior to coring, for which it is ideally suited.

Specification

  • Centre Frequency: 1.5 GHz
  • Penetration Depth: up to 400 mm
  • Uses: detection of rebar, conduits and post-tension cables
  • Manufactured by: GSSI

GSSI StructureScan Mini XT

The GSSI StructureScan Mini XT

The StructureScan Mini XT is an all-in-one GPR system for concrete inspection. With a 2700 MHz antenna, this handheld system is useful for rebar detection to depths of up to 400 mm. Integral software on the 3D model provides a plan view of reinforcement. The system can also be used with the following accessories: Palm XT external antenna, LineTrac XT, and an extension pole.

Specification

  • Centre Frequency: 2700 MHz
  • Penetration Depth: up to 350 mm in concrete
  • Uses: detection of rebar, conduits and post-tension cables, voids and slab thickness measurement
  • Manufactured by: GSSI