Groundtech GR-3 Series Overview
The Groundtech GR-3 and GR-3 PLUS are gradiometer ground scanners. Instead of transmitting into the ground like a coil detector, a GR-3 measures small changes in the magnetic field as you walk, and the Conrad GR-3 app turns those readings into color 3D graphics in real time and stores them for later analysis. Groundtech says the graphics separate magnetic metals such as iron and steel from non-magnetic metals such as gold, silver and copper, and show empty spaces such as tunnels and chambers. Both models have four modes, run up to 10 hours on an internal 3.7 V 3.2 Ah lithium-ion battery that charges over USB Type-C, connect over Bluetooth 4.2 BLE and carry Groundtech's 2-year warranty. Groundtech lists them for sandy, rocky and clay soil.
Our practical advice: a 3D scan shows you an anomaly, its rough size and depth, not a coin-style target ID. What it is gets settled with a shovel, so the GR-3 Series suits people who are prepared to dig on a scan result.
Groundtech GR-3 vs GR-3 PLUS: Which Should You Buy?
The GR-3 and GR-3 PLUS share the same body, modes, battery, app and box. The difference is the sensor and the depth it gives: the GR-3 uses Single CN-D sensor technology and is rated up to 7 meters (23 ft), and the GR-3 PLUS uses Dual CN-D sensor technology and is rated up to 15 meters (49 ft). Both are maximum ratings that depend on target size and soil.
Our recommendation: if what you are looking for was buried by hand, the GR-3 rating is usually enough and the plain GR-3 is the simpler buy. Choose the GR-3 PLUS when you are searching for something you believe sits deeper, such as structures or voids under fill, and the extra rated depth is the reason you are buying a scanner at all.
Groundtech GR-3, Best For:
- A first 3D scanner for caches and relics
- Running a survey from the phone or tablet you already own
- Carrying a one-piece wand with no cables on long walks to the site
Groundtech GR-3 PLUS, Best For:
- Looking for structures, tunnels or voids under fill
- Buyers who want the GR-3 way of working with more rated depth
Key Features in the Field
The four GR-3 modes cover a survey from start to finish. Automatic and Manual ground scanning build the 3D image as you walk a grid. Live Scan gives immediate feedback as you walk freely, and we like it for a first look at a site before you mark out a grid. The Pinpointer function fixes a target's position on the surface so you know exactly where to put the shovel. The Conrad GR-3 app runs in 23 languages. Consistent scanning matters more than any setting: walk every line of the grid at the same pace, in the pattern the Groundtech manual sets out, because a line walked slowly next to one walked quickly makes the data hard to read and a real anomaly can look like noise. We would learn that pattern on known ground before the first real survey.
Where the GR-3 Series Works Best and Its Limits
A Groundtech GR-3 Series scanner earns its keep when you already know where you want to look, such as an old homestead, a cellar hole or the corner of a field. Mark out the area, walk it in Automatic or Manual mode, and use the 3D image to pick where a hole is worth digging. In our experience it is most interesting for possible buried structures, large ferrous objects and unusual ground.
The limits are worth knowing before you buy. A GR-3 has no screen of its own, so charge the phone as well as the wand. Groundtech publishes no waterproof rating, so treat both models as dry-ground tools, and Groundtech rates them for use from minus 10 to 60 °C (14 to 140 °F). Our page on how deep metal detectors go explains why rated depth and real depth differ.
GR-3 Series, GR-4 Series or A2 Series
The Groundtech GR-4 Series is the step up when you would rather not depend on a phone in the field. Groundtech gives the GR-4 the same rated depth as the GR-3 PLUS, so the extra money buys a built-in screen and the newer interface rather than more rated depth, and we would pick the GR-4 over the GR-3 for that interface and the G-Portal software. The GR-4 DUAL adds a pulse-induction metal detector.
The Groundtech A2 Series is Groundtech's deepest-rated line, with a pulse-induction detector and three coils, and the A2 GEO adds a geo-electric system for groundwater and deep cavities. Buy into the A2 Series only if you need that depth or those instruments; for a first scanner on known ground, a GR-3 Series model is the lower-cost way in.
What Comes in the Box and What to Add
Groundtech's standard contents are the same for both GR-3 Series models: the main unit, a 25 W charging adapter and USB-C charging cable, a carrying case and the user manual.
For recovering the target once you have dug down, a pinpointer saves a lot of hole widening; Groundtech's own IQ Pointer pinpointer and IQ Detect underwater detector are here.
Groundtech 3D Scanner Comparison
All six Groundtech scanners use a plus or minus 2000 µT gradiometer sensor and differ in rated depth, extra instruments, display and battery.
| Feature | Groundtech GR-3 | Groundtech GR-3 PLUS | Groundtech GR-4 | Groundtech GR-4 DUAL | Groundtech A2 | Groundtech A2 GEO |
|---|
| Instruments | 3D scanner | 3D scanner | 3D scanner | 3D scanner and PI detector | 3D scanner and PI detector | 3D scanner, PI detector and geo-electric system |
| Rated 3D scan depth | Up to 7 m (23 ft) | Up to 15 m (49 ft) | Up to 15 m (49 ft) | Up to 15 m (49 ft) | Up to 20 m (66 ft) | Up to 20 m (66 ft) |
| Scanner sensor | Single CN-D gradiometer, ±2000 µT | Dual CN-D gradiometer, ±2000 µT | MFS-2 dual gradiometer, ±2000 µT | MFS-2 dual gradiometer, ±2000 µT | MFS-3 dual gradiometer, ±2000 µT | MFS-3 dual gradiometer, ±2000 µT |
| PI metal detector | None | None | None | 404 Hz, PiD35 coil | 500 Hz, three coils: 9.5 x 6.5, 11.75 x 8 and 14.5 x 10 inch | 500 Hz, three coils: 9.5 x 6.5, 11.75 x 8 and 14.5 x 10 inch |
| Rated detector depth | None | None | None | Up to 3 m (10 ft) | Up to 1.5 m (5 ft) | Up to 1.5 m (5 ft) |
| Geo-electric system | None | None | None | None | None | 4-line resistivity, 4 probes on 25 m (82 ft) cables |
| Scanning modes | 4 | 4 | 3 | 5 | 6 | 8 |
| Display | Your phone or tablet | Your phone or tablet | Built-in, 240 x 280 px, 850 cd/m² | Built-in, 240 x 280 px, 850 cd/m² | Built-in, 480 x 320 px, 180 cd/m² | Built-in, 480 x 320 px, 180 cd/m² |
| App and Bluetooth | Conrad GR-3 app, Bluetooth 4.2 BLE | Conrad GR-3 app, Bluetooth 4.2 BLE | G-Portal 3D and 4D, Bluetooth 5 (LE) | G-Portal 3D and 4D, Bluetooth 5 (LE) | G-Portal 3D and 4D, Bluetooth 5 (LE) | G-Portal 3D and 4D, Bluetooth 5 (LE) |
| Scans saved on the unit | In the app | In the app | 10 | 10 | 5 | 5 |
| Battery and runtime | 3.7 V 3.2 Ah, up to 10 hours | 3.7 V 3.2 Ah, up to 10 hours | 7.2 V 3.2 Ah, up to 10 hours | 7.2 V 3.2 Ah, up to 10 hours scanning, 6 hours PI | 3.6 V 9.6 Ah, up to 10 hours scanning, 6 hours PI | 3.6 V 9.6 Ah, up to 10 hours scanning and geo-electric, 6 hours PI |
| Weight | 600 g (21.2 oz) | 605 g (21.3 oz) | 760 g (1.7 lb) | 1,364 g (3.0 lb) | 1,135 to 1,696 g (2.5 to 3.7 lb) by sensor or coil | 1,180 to 1,742 g (2.6 to 3.8 lb) by sensor or coil |
| Waterproof rating | None published | None published | None published | None published | None published | None published |
| Warranty | 2 years | 2 years | 2 years | 2 years | 2 years | 2 years |
Our Groundtech buyer's guide compares the full Groundtech range. Scan only where you have permission; our metal detecting laws and ethics page is a place to start.
Why Buy the Groundtech GR-3 Series from Serious Detecting?
- Free Shipping on Orders Over $99: Your Groundtech GR-3 or GR-3 PLUS ships at no extra cost across the continental US.
- Authorized Groundtech Dealer: Showroom in Ypsilanti, Michigan, full 2-year manufacturer warranty and product registration support.
- Help Before and After You Buy: Our staff answer setup, app and GR-3 Series questions by phone or email.
GroundtechSale Price $1,300.00 Regular Price
GroundtechSale Price $1,600.00 Regular Price
