Basic information

A simple, quick introduction to... Ground Penetrating Radar.

What is GPR?

Ground penetrating radar (GPR) is an advanced, non-invasive sub-surface imaging technique that typically uses short pulses of electromagnetic energy to ‘see’ into the ground.  GPR can image through soil, concrete, tarmac, rock, wood, ice and even water.  It is quick, easy to use and inexpensive in comparison to other investigation methods.  It is capable of probing down to a few tens of metres (depending on the system type & ground conditions) and provides the user with a ‘cross-sectional’ image of the sub-surface.

GPR is very good at determining the shape, size, extent and depth of a buried object.  It can be used to find pipes, foundations, voids, trenches, geological layers, re-inforcing bars, etc.  It works best in dry ground environments but can also work well in wet, saturated materials.  It does not work very well in saline conditions and through dense clays.

GPR is used by a wide range of people including:

  • Civil Engineers & NDT Archaeologists
  • Geologists
  • Geotechnical Engineers
  • Glaciologists
  • Forensic Investigators
  • Environmental Scientists
  • Hydrologists

In fact, anyone who needs to investigate buried features.  It is particularly popular for utility detection and roadway evaluation.

GPR in action

As the GPR system is moved across the surface, pulses of electromagnetic energy are directed into the ground from a transmitting antenna.  The energy travels though the ground where buried objects reflect/scatter part of the energy back to the surface, which is picked up by the GPR’s receiving antenna.  These returning signals are converted in to a GPR section (or radargram) which is displayed on a computer screen in real-time.  The operator then uses knowledge, skill and experience to assess the data and interpret the features seen in the section.

Antenna centre frequency (MHz)Approximate imaging depth in soil (metres)Approximate target size in soil (metres)
1500 0.3 0.03
1000 1 0.1
500 2 0.2
250 3 0.3
100 5 0.5
50 10 1
20 20 2

Surveys are usually conducted along profile lines (to produce 2D sections). However, any number of closely spaced lines can be combined to create a 3D volume of data.  GPR systems are designed to use different antenna frequencies (typically 20-1500MHz).

Low frequency systems (20-250MHz) penetrate the deepest, but only image larger objects.  These tend to be used for hydrological, glacial and geological work.  Higher frequency systems (>250MHz) see smaller objects but don’t penetrate as deep. These are more commonly used for civil engineering and NDT applications.

GPR is perfectly safe to use but, as with any site technique, appropriate heath and safety risk assessments must be made before carrying out an investigation.  To use a GPR system in the EU, operators need to have an appropriate and up-to-date licence, be adequately trained, responsible and follow a code of practice.  Operators must ensure that their surveys do not interfere with any vital telecommunications systems (e.g., aircraft, hospitals, defense, etc).

 

Guidelines for the use of GPR equipment

EuroGPR is committed to the adoption of best practices for the use of GPR technology in all applications. At present there are no recognized International Standards but a number of guidances and recommendations are used in different countries and across different GPR applications. EuroGPR provides some facts sheets for guidance in GPR surveys on different applications. For completeness , this page includes also references originated by other entities. EuroGPR takes no responsibility for their content nor endorses them but simply acknowledge their existence.

Members EuroGPR and visitors of this website are encouraged to report to the This email address is being protected from spambots. You need JavaScript enabled to view it.should they feel a relevant document should be added to the following list.

Guidelines for utilities

Utilities detection is certainly the biggest commercial application for GPR. EuroGPR statement below is the official recommendation of the association. Guidelines to the use of GPR, usually embedded into more general guidelines from utilities mapping, are listed below in an attempt to give members the widest possible picture; however. EuroGPR does not endorse such guidelines.

  • EuroGPR policy statement on utilities detection and mapping.
  • Association pour la qualité en Géophysique Appliquée non Pétrolière (AGAP), Guide d'adéquation des méthodes et techniques géophysiques aux applications concernant le sol et le sous-sol (guideline for the update of geophysical methods and techniques for soil and sub-soil applications), 1992.
  • American Society of Testing and Materials (ASTM), Standard Guide for Using the Surface Ground Penetrating Radar Method for Subsurface Investigation, ASTM D 6432-99, 1999
  • American Society of Civil Engineers (ASCE) Standard Guideline for the Collection and Depiction of Subsurface Utility Data, CI/ASCE 38-02, 2002
  • Comitato Elettotecnico Italiano (CEI) Norma per l’impiego del radar per introspezione del suolo per prospezioni preliminari ad opere di posa di servizi ed infrastrutture sotterranee (Regulations for performing preliminary surveys with ground probing radar before laying underground utilities and infrastructures), CEI 306-08, 2004
  • Fondazione Politecnico di Milano, Sistemi geognostici per la mappatura dei sottoservizi (Mapping subsurface utility networks using geognostic investigations)
  • The Survey Association Guidance Note, “Utilities Surveys, detailed guidance notes for specifying a utility survey”, Issue 1, November 2009. Available in low and high resolution from TSA website at http://www.tsa-uk.org.uk/guidance.php

Guidelines for archaeology

As a rapidly growing sector, the archaeological industry has come to consider GPR as a standard extension of the more established geophysical techniques, rather than a novel addition. The wide range of targets, and thus scope of responses which may need to be identified, means that survey strategies will vary greatly from one project design to another. However, for any given situation, the basic considerations and controlling physical limitations that are key to defining the "best" approach will typically remain the same. In a similar way to utility mapping, the current guidelines tend to be part of documents with a far wider scope, the primary examples of which have been listed below. Again, inclusion on this list does not necessarily imply EuroGPR endorsement of the document.

Guidelines for pavements

This document aims to provide guidance to EuroGPR association members to ensure they undertake GPR surveys on pavements in a safe and responsible manner.  It is not meant to provide a specification of how every variation of pavement GPR survey should be performed.  EuroGPR members are required to conform to any local or national specification for these surveys that may be already in place.

Guidelines for crime scene investigation

EuroGPR worked with the UK Government's Forensic Science Regulator (FSR) to ensure that Association Members are fully aware of the current developments of Quality Standards in scene of crime investigations and that these same standards are appropriate for our technology and methodology, based on Members' experience. This has led to the document here below.

Guidelines for other applications

Hints and tips for international GPR shipping

 

Glossary of common GPR terms

The EuroGPR Association Glossary of GPR terms - click to open PDF

EuroGPR is pleased to make this expanded glossary of GPR terms available for general release on the EuroGPR Association website. It has been produced by a collaboration of a number of experts in the field of GPR.

In particular we would like to thank the contributions from Giovanni Alli, Michael Arvantis, Stefan van der Baan, Andy Kathage, Neil Linford, Elmar Strobach, Adam Szynkiewicz and Vincent Utsi.

There are a number of other contributors for whom we do not have details but equally wish to thank.

Where terms have been suggested but no definition provided we have turned to Wikipedia, there is a note in the right column where this has occurred.

Please note that this is a live document and we encourage users of the glossary to give us feedback on:

a) the accuracy of the definitions and if necessary suggest alternatives

b) offer definitions where none have be provided (cells marked in orange)

c) offer new terms which need adding and where possible how they should be defined.

Feedback should be sent to This email address is being protected from spambots. You need JavaScript enabled to view it.

Peter Barker

Glossary Editor