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EnviroPhysics, Inc.
Ground-Penetrating Radar (GPR) Surveys
GPR advantages:
1.) Fast data collection
2.) Able to detect voids and trenches
3.) Able to determine depths and lengths of targets

GPR disadvantages:
1.) Terrain must be flat and even
2.) Doesn't work well in clay
Typical GPR data showing three pipes
Some targets can only be found by ground-penetrating radar (GPR). These include graves,voids, foundations, trenches, and other structures often associated with archaeological, police or scientific research projects. Of course, GPR can also be used to help define more common targets like pipes and tanks.

GPR works by transmitting a high frequency electromagnetic pulse into the ground, and then graphically recording the portion of that signal that is reflected back to the transmitting antenna from subsurface structures. When the buried structure has a definite shape (like a tank, for example), then the radar image that is reflected back from it can be identified. GPR is also good at defining areas where natural sedimentary layering has been disturbed (formerly excavated areas like trenches and graves).

Penetration of radar energy into the ground varies from site to site. In general, sandy dry areas are best for radar, with useable data down to a depth of ten feet or more. Where the soils are clay-rich and the water table is high, useable radar data may not be seen more than a foot or two into the ground.
GPR survey to detect voids at McGuire air base
GSSI-SIR-2000 GSSI-SIR-3000
GSSI-SIR-2000 is a third generation digital single channel radar system equipped with integral car and GPS capability. The GSSI-SIR-3000 is the fourth generation radar system capable of 3-dimesional data collection. Both systems are carried to all sites to ensure completion of the project in case one system fails for any reason.
US Radar 500 mhz
This British-designed, NJ manufactured radar system is considered as one of the best of its kind for work in tight quarters and silt/clay soil conditions. The electronics in this unit were completely upgraded at the factory with the newest design in 2008. Software updates are installed as soon as they are available.
200 mhz GSSI SIR-3000
This cart-based system allows for one-person operation. It is designed to detect deep targers or targets in areas with clay-rich soils. The modified Vermeer cart system makes the use of this powerful antenna as efficient as the 500 mhz systems and ensures thorough radar coverage of any site.
GSSI SIR-3 (right) with 300 and 500 mhz antennas (left and center)
A first generation digital Subsurface Interface Radar (SIR) designed for a broad range of environmental, geotechnical, geological, and engineering applications. This is EnviroPhysics' original GPR and while it's no longer used, it provides a good contrast to the current digital systems. When EnviroPhysics bought it new in 1992, it was state of the art.
Buried pipes 1 to 4 feet deep
Tank void (excavated area)