Groundtech GR-4 DUAL 3D Ground Scanner and Integrated Pulse Induction Metal Detector

The Groundtech GR-4 DUAL combines a 3D ground scanner and a 404 Hz pulse induction metal detector in one standalone unit, for treasure hunters and relic hunters who want to survey an area and then search it with a detector without changing machines. Groundtech gives a 3D scanning depth of up to 15 meters (49 feet) and a detector depth of up to 3 meters (10 feet), both depending on the target and the soil. The built-in screen runs everything in the field, and the G-Portal app on Android and iOS adds 3D and 4D analysis.

What is in the box with the Groundtech GR-4 DUAL

Groundtech's standard contents for the GR-4 DUAL

• Groundtech GR-4 DUAL main unit with built-in screen
• MFS-2 Dual Sensor module
• PiD35 detector search coil
• Charging adapter
• Carrying bag
• User manual

A 3D ground scanner and a pulse induction detector

Groundtech says the 3D Ground Scanning System detects, measures and locates buried metals, magnetic objects, graves, rooms and cavities such as tunnels, and that the results graphically show magnetic metals (iron or steel) and non-magnetic metals (gold, silver or copper). The MFS-2 dual sensor gradiometer has a measurement range of plus or minus 2000 microtesla and works with a 480 MHz processor and a 12-bit A/D converter. The integrated pulse induction detector runs at a 404 Hz pulse frequency with the PiD35 coil, and Groundtech gives up to 3 meters (10 feet) for the detector system and up to 15 meters (49 feet) for 3D scanning. 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.

Five scanning modes

• 3D Ground Scanning: a systematic survey that maps the area in three dimensions.
• Live Scanning: graphically shows underground objects without a fixed search pattern.
• Pinpointer: helps locate the exact position of an object.
• Detector Fast Scan: fast searching with the pulse induction detector.
• Detector Advanced Scan: Groundtech says it offers detailed settings, deeper detection and ferrous and non-ferrous discrimination.

How the two systems work together

Picture an old property. A magnetic scan picks out an unusual area, and you want to know whether metal is there. The pulse induction detector gives you a second way to check. We like that the two technologies give you different information, but combining them does not guarantee an accurate identification of the target.

Built-in screen and the G-Portal app

Settings, active modes and results show on the built-in screen, so no phone or tablet is needed to start, and the GR-4 DUAL stores up to ten 3D scans on the device. Over Bluetooth 5 (LE), the G-Portal (Groundtech Portal) app for Android and iOS saves scan data, shows 3D and 4D analyses and generates reports. Groundtech lists 11 languages on the device and 25 languages in the app.

Design and battery

The GR-4 platform has a foldable modular body, an adjustable grip angle and a removable sensor module. The 7.2 V, 3.2 Ah rechargeable lithium-ion battery runs up to 6 hours in pulse induction detector mode and up to 10 hours of 3D scanning, according to Groundtech, and charges over USB Type-C with a 25 W charging adapter. The GR-4 DUAL weighs 1364 grams (3.0 pounds), and Groundtech gives an operating temperature range of minus 10 to 60 °C (14 to 140 °F).

For 3D scanning without the detector, Groundtech makes the Groundtech GR-4; for deeper 3D scanning and two detector coils, see the Groundtech A2.

Who the Groundtech GR-4 DUAL suits

The GR-4 DUAL suits buyers who want more than magnetic anomaly scanning. It has the magnetic ground scanning of the GR-4 plus an integrated pulse induction metal detector, which makes it more versatile than the standard GR-4. We would recommend it when you specifically want both magnetic scanning and pulse induction detection. If you only need magnetic scanning, the standard GR-4 may be enough. Its strongest point is a 3D magnetic scanner and a pulse induction detector in one unit.

What the pulse induction detector adds

Pulse induction responds to conductive metal objects, non-ferrous metals included, and it works on a different principle from the magnetic scanner. The integrated detector does not necessarily give you conventional coin-style target identification.

One mistake to avoid with the GR-4 DUAL

The biggest mistake is assuming the two systems do the same job. They measure different physical properties, so a response from one system does not guarantee a matching response from the other.

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 GR-4 DUAL specifications

Groundtech covers the GR-4 DUAL with a 2-year warranty.

Every GR-4 model we carry is in our Groundtech GR-4 collection, and our Groundtech buyer's guide compares the full Groundtech range.