Groundtech A2 GEO 3D Ground Scanner & Metal Detector

The Groundtech A2 GEO adds a geo-electric resistivity system to the A2's 3D ground scanner and 500 Hz pulse induction metal detector, for survey work where you are looking for underground water, cavities and deep structures as well as metal. Groundtech gives the 3D scanner up to 20 meters (66 feet), depending on the target and the soil, and says the geo-electric system detects groundwater, tunnels, tombs and caves at greater depths. Four conductive probes and four 25 meter (82 foot) conductor cables come in the box.

What is in the box with the Groundtech A2 GEO

Groundtech's standard contents for the A2 GEO

• Groundtech A2 GEO main unit
• MFS-3 Dual Sensor module
• PiD25 detector search coil
• PiD30 detector search coil
• 4 conductive probes
• 4 conductor cables, 25 m (82 feet) each
• Headset
• Charging adapter
• Carrying bag
• User manual

The geo-electric resistivity system

Groundtech lists the A2 GEO's resistivity system at 100 V DC and 66 mA output, 62 Hz, with a 50 sample interval. The four conductive probes go into the ground, the four 25 meter (82 foot) cables connect them, and the system runs in Resistivity Automatic Scanning or Resistivity Manual Scanning. Groundtech says it detects groundwater, tunnels, tombs and caves at greater depths, and the results are analyzed in 3D and 4D in the G-Portal app. Groundtech gives no depth figure for the resistivity system, so we would not quote one.

MFS-3 dual sensors and 20 meter 3D scanning

The MFS-3 dual sensor gradiometer has a measurement range of plus or minus 2000 microtesla and works with a 240 MHz processor and a 12-bit A/D converter, and Groundtech gives up to 20 meters (66 feet) for 3D scanning and up to 1.5 meters (4.9 feet) for the detector system. Groundtech's maximum depth figure depends on the target's size and the soil structure, so we would expect small objects to read at much shallower depths than the headline figure.

Eight scanning modes

• 3D Ground Scanning: Groundtech says it detects, measures and locates buried metals, magnetic objects, graves, rooms and cavities such as tunnels.
• Live Scanning: graphically shows underground objects without a fixed search pattern.
• Pinpointer: helps locate the exact position of an object.
• Detector Fast Scan: separates ferrous from non-ferrous metals as you search.
• Detector Advanced Scan: detailed settings and deeper detection, with ferrous and non-ferrous discrimination.
• 3D Detector Scan: detects soil and metals with the detector and analyzes the results in 3D.
• Resistivity Automatic Scanning and Resistivity Manual Scanning: the two geo-electric modes, run with the probes and cables.

Screen, app and battery

Settings and results show on the built-in 480 x 320 pixel screen, the A2 GEO stores five 3D scans on the device, and over Bluetooth 5 (LE) the G-Portal app for Android and iOS adds 3D and 4D analysis. Groundtech lists 11 languages on the device and 25 languages in the app. The 3.6 V, 9.6 Ah rechargeable lithium-ion battery runs up to 6 hours with the pulse induction detector and up to 10 hours with the 3D scanning and geo-electric systems, charged over USB Type-C with a 25 W charging adapter. Groundtech gives an operating temperature range of minus 10 to 60 °C (14 to 140 °F).

Without the resistivity system, the same scanner and detector come in the Groundtech A2.

Who the Groundtech A2 GEO suits

The A2 GEO suits buyers who want several geophysical investigation methods in one system. It adds a third method to the A2 platform: alongside magnetic scanning and pulse induction detection, it has a geo-electrical resistivity system. We would recommend it when you specifically need resistivity measurements on top of the other A2 functions. If your focus is metal detection and magnetic anomalies, the standard A2 may be enough. Its strongest point is magnetic, pulse induction and geo-electrical measurement in one unit.

What resistivity measures

Picture a site where you suspect an underground cavity or a moisture-related anomaly. Electrical resistivity measurements show differences in how the ground below conducts electricity, which can point to areas worth investigating further.

Three systems, three properties

The A2 GEO combines magnetic scanning, pulse induction metal detection and electrical resistivity measurement. We like that each system investigates a different physical property. You get the most from it when you understand what each method actually measures.

One mistake to avoid with the A2 GEO

The biggest mistake is reading a resistivity anomaly without knowing the ground. Different soils, moisture levels and geological formations change the readings, so we would learn the site before deciding what an anomaly is.

Permission and protected sites

We would get the landowner's permission before any survey and check the laws that protect historic sites, archaeological sites and burials where you plan to scan. A Groundtech scanner can show where something is different underground; it does not tell you whether you may dig there.

Groundtech A2 GEO specifications

Groundtech covers the A2 GEO with a 2-year warranty.

Both A2 models are in our Groundtech A2 collection, and our Groundtech buyer's guide compares the full Groundtech range.