This document provides information about using ground penetrating radar (GPR) to locate underground utilities and services. It discusses the GPR equipment and frequencies used, including 250MHz and 750MHz antennas, and how they impact resolution and depth of detection. It also outlines ideal ground conditions for GPR use, including dry soils with low conductivity. The document describes some common applications of GPR like locating buried pipes and tanks, and measuring pavement and concrete thickness. It cautions that GPR interpretations are based on judgments and Geotechnics does not guarantee accuracy.

1. Marking Underground Services
using Ground Penetrating
Radar (GPR)
To enable us to provide an efficient
service, we require the following:
• HS documentation
• Clear work brief
• Your test location to be accessible and
clear of debris
• Service plans for the following utilities:
- Power
- 3 Waters (City Council)
- Gas
- Telecommunication (including fibre optic).
If you are unable to provide service plans,
we are able to obtain them on your behalf,
however a period of 3 days notice may be
required. Additional cost will apply.
For rates or additional information please
feel free to get in touch.
Marking Standards Guide for
GPR (SCIRT regulations)
Our fully trained team provides a one stop shop for all your service location needs.
We can obtain service plans, provide on-site marking and provide service depth
measurements (accurate to 50mm). Coupled with our Cable Avoidance Tool (C.A.T
genny), this comprehensive service is designed to give you confidence before you dig.
If you require rates or additional information, please feel free to contact us.
Power (PWR)
Waste water (WW or SS)
Water (H20)
Storm water (SW)
Gas (GAS)
Telecommunication (T/COM)
Fibre optic (FBR)
Unidentified service (??)
Example
GEOTECHNICS LTD
45A Parkhouse Road, Wigram Christchurch 8042 | PO Box 13055, Christchurch 8141, New Zealand
p. +64 3 361 0300 | e. christchurch@geotechnics.co.nz | www.geotechnics.co.nz

2. General GPR information
Use GPR for:
- Location underground utilities
- Locate burst water pipes
- Measure pavement thickness
- Locate bedrock down to 6m (ideal conditions)
- GPR surveys
- Factual reports
- Measure concrete slab thickness
- Identifying geological or man made
anomalies
- Identify rebar in concrete
- Locate Underground Storage Tanks (UST’s)
- Locate human remains
- Locate unexploded ordnance
- Identify underground tunnels.
GPR performance summary
250 MHz
Lower frequency Longer wavelength Bigger antenna Lower resolution, lower senility, greater
depth, less ground clutter
750 MHz
Higher frequency Shorter wavelength Smaller antenna Higher resolution, Higher senility,
shallower depth, more ground, clutter
Low conductivity
(Excellent radar conditions)
- air
- dry granite,dry limestone
- concrete,asphalt
Medium conductivity
(Medium radar conditions)
- freshwater, ice, snow
- sand, silt, dry clay, basalt,
seawater ice
High conductivity
(Poor radar conditions)
- wet clay, wet shale
- seawater.
Ideal ground conditions
for GPR
GEOTECHNICS LTD
45A Parkhouse Road, Wigram Christchurch 8042 | PO Box 13055, Christchurch 8141, New Zealand
p. +64 3 361 0300 | f. +64 3 341 0219 | e. christchurch@geotechnics.co.nz | www.geotechnics.co.nz
Specifications
At Geotechnics we use a combination of relevant Service Plans, Ground Penetrating Radar and Digital Service locators
to assist us to minimize your risk of striking underground services while digging, drilling or probing into the ground. Depth
of exploration is dependent on the electrical properties of the material(s) inspected. Our interpretations are based on
judgments made from the acquired radar signals and/or data. Geotechnics does not guarantee the accuracy or
correctness of interpretations. Geotechnics will not accept liability or responsibility for any loss, damage or expense
that may be incurred or sustained by any services as a result of interpretations performed by us.
Depth (m) Xmin: -0.21; Xmax:
Move start time
Background removal
Vertical bandpass filter
Linear gain
Smoothed gain
0.50
1.00
1.50
2.00
2.50
3.00
3.50
250 MHz
Depth (m)
0.50
1.00
1.50
2.00
2.50
3.00
3.50
750 MHz