GR-4 or GR-4 DUAL: What the DUAL Adds
The Groundtech GR-4 and GR-4 DUAL use the same MFS-2 dual gradiometer sensor (plus or minus 2000 µT), the same 240 MHz processor and the same built-in color screen, and Groundtech rates the 3D scan on both at up to 15 meters. The GR-4 has three modes: 3D Ground Scanning, Live Scanning and the Pinpointer function. The GR-4 DUAL adds a 1 kHz pulse-induction metal detector with the PiD35 search coil in the box, plus Detector Fast Scanning, Detector Advanced Scanning and a 3D Ground Scanning Detector mode. Groundtech says the detector separates ferrous from non-ferrous metal and rates it to about 3 meters. Groundtech's own page lists five modes in one place and six in another for the DUAL; the difference is the 3D Ground Scanning Detector mode.
Our recommendation: buy the plain GR-4 if you already own a good detector and pinpointer for recovery, because the scanner is the part you are paying for. Buy the GR-4 DUAL if you want one unit that scans deep and then works the top layers of the same spot, with no second machine to carry.
Working From the Built-In Screen
The built-in screen is the main difference between a GR-4 Series unit and the phone-based Groundtech GR-3 Series. Settings, the active mode and the scan graphics show on the device, so you can run a survey without a phone in your hand. Pair over Bluetooth 4.2 BLE with the G-Portal app for Android and iOS when you want to save scans, look at them in 3D and 4D, and produce a survey report. The body folds, the grip angle adjusts and the sensor module is removable, which Groundtech highlights for transport.
In practice we tell customers to treat the screen as the field tool and G-Portal as the desk tool: scan and mark on site, then go over the saved scans before deciding where to dig.
Battery, Box and Accessories for the GR-4 Series
Both GR-4 Series units run on a rechargeable 3.7 V lithium-ion battery and charge over USB Type-C, with support for a 25 W adapter. Groundtech rates about 10 hours in 3D scanning; on the GR-4 DUAL the pulse-induction detector mode runs about 6 hours. Groundtech's box list for the GR-4 is the main unit, the MFS-2 dual sensor, a charging adapter, a carrying bag and the user manual; the GR-4 DUAL box adds the PiD35 detector coil. Groundtech gives a 2-year warranty.
Groundtech lists no optional coils, sensors or other accessories for the GR-4 Series, and it does not say whether a GR-4 can be converted to a GR-4 DUAL later, so decide on the detector before you buy. Groundtech publishes no water-resistance rating for either unit. A pinpointer still earns its place for the last few inches of the hole; see Groundtech pinpointers.
When the GR-3 Series or A2 Series Is the Better Buy
The Groundtech GR-3 Series is the cheaper route if a phone as the display does not bother you. Groundtech rates the GR-3 PLUS at the same up to 15 meters as the GR-4, in a 600 g one-piece wand, so you give up the built-in screen and the folding body but not rated depth.
The Groundtech A2 Series is the step up. Groundtech rates the A2 at up to 20 meters with the higher-range MFS-3 sensor (plus or minus 3000 µT), and the A2 includes a pulse-induction detector with both the PiD25 and PiD30 coils and a headset. The A2 GEO adds a geo-electric system for groundwater and deep cavities. If the GR-4 DUAL is already on your list and you expect to work deeper sites, compare it against the A2 before you decide.
Gradiometer Scan and Pulse Induction: Two Different Readings
On a GR-4 DUAL, the 3D scan and the pulse-induction detector answer different questions, and it helps to know which one you are reading. The MFS-2 gradiometer scan responds to magnetic disturbance in the ground, so Groundtech says it shows iron and steel differently from gold, silver and copper, and shows voids such as tunnels and rooms. The 1 kHz pulse-induction detector transmits into the ground and responds to any metal near the coil, which is why it suits checking a marked spot before and during the dig. The plain GR-4 gives you the first reading only. Our metal detector technologies explained page covers how pulse induction works, and how deep metal detectors go explains why rated depths are ceilings rather than typical results. Scan only where you have permission; see metal detecting laws and ethics.
The GR-4 and GR-4 DUAL were both on Groundtech's current lineup page in October 2026.
