What the Groundtech GR-3 Series Is
The Groundtech GR-3 Series 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 GR-3 app turns those readings into color 3D graphics. 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 the same four modes: Automatic and Manual ground scanning for walking a grid, Live Scan for free searching without a fixed pattern, and a Pinpointer function to fix a target's position on the surface before you dig.
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.
GR-3 and GR-3 PLUS: The Two Configurations
The GR-3 and GR-3 PLUS share the same body, weight, four scanning modes, battery, app and box contents in Groundtech's specification table. The difference Groundtech publishes is depth: up to 7 meters for the GR-3 and up to 15 meters for the GR-3 PLUS, both depending on the size of the target and the soil structure. These are Groundtech's maximum ratings, not depths you should expect on every target. Groundtech's own pages are not consistent on two points: the GR-3 PLUS page text gives the GR-3 up to 10 meters, while both specification tables say 7, and the page text describes a single sensor in the GR-3 and a dual sensor in the GR-3 PLUS while the table lists CN-D dual sensor technology for both.
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.
What Comes With a GR-3 Series Scanner, and What to Add
Groundtech lists the same box for both GR-3 Series models: the main unit, a 5 volt charging adapter and cable, a carrying case, the user manual and a warranty certificate. Groundtech gives a 2-year warranty. The battery is an internal 3.7 V lithium-ion pack rated at about 8 hours, it charges from 5 volt USB, and Groundtech says it can be charged from a portable power bank, which helps on a long day away from the truck.
You supply the display: an Android or iOS phone or tablet with Bluetooth 4.2 BLE for the GR-3 app. Groundtech lists no optional sensors, coils or other accessories for the GR-3 Series, and it publishes no water-resistance rating, so treat a GR-3 as a dry-ground tool. For recovering the target once you have dug down, a pinpointer saves a lot of hole widening; Groundtech's own IQ Pointer and IQ Detect pinpointers are here.
When the GR-4 Series or A2 Series Is the Better Buy
The Groundtech GR-4 Series is the step up when you would rather not depend on a phone in the field. The GR-4 has its own built-in color screen, a folding body with a removable sensor module, and the G-Portal app for 3D and 4D analysis afterward. Groundtech rates the GR-4 at up to 15 meters, the same figure as the GR-3 PLUS, so the extra money for a GR-4 buys the screen and the build rather than more rated depth. The GR-4 DUAL adds a pulse-induction metal detector for the upper soil layers.
The Groundtech A2 Series is Groundtech's deepest-rated line, up to 20 meters with a higher-range MFS-3 sensor, and it includes a pulse-induction detector with two coils. 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.
Before You Walk Your First GR-3 Grid
A Groundtech GR-3 Series scanner earns its keep when you already know where you want to look, such as an old homestead or the corner of a field. Mark out the area, walk it in Automatic or Manual Ground Scan, and use the 3D image in the app to pick where a hole is worth digging. Charge the phone as well as the wand, because the GR-3 has no display of its own. Groundtech's 7 and 15 meter figures are maximums that depend on target size and soil; our page on how deep metal detectors go explains why rated and real-world depth differ. Permission comes first on any ground, and our metal detecting laws and ethics page is a place to start.
Groundtech's site listed both the GR-3 and GR-3 PLUS as current models in October 2026.
