Comparison guide · 6-min read
GPR vs cover meter for rebar. Different tools, different jobs.
Both find rebar — but they answer different questions. A cover meter (pachometer) is a fast, cheap way to measure concrete cover over shallow bars; GPR images the whole subsurface, finding rebar, conduit, post-tension cable, and voids at real depth before you cut. Knowing which to reach for keeps a core clear and a survey honest.
TL;DR
Use a cover meter when the only question is concrete cover over the top mat of rebar — it's fast, inexpensive, and accurate at shallow depth. Use GPR for anything more: locating deeper bars, distinguishing rebar from conduit and post-tension cable, mapping a second mat, finding voids, and — critically — clearing a core or cut location, where a cover meter's blindness to non-rebar targets and limited depth makes it unsafe to rely on alone. For coring clearance, GPR isn't optional; a cover meter can't see the conduit or tendon that ends the job.
Side-by-side comparison
| Feature | Ground-Penetrating Radar Images everything in the slab | Cover Meter (Pachometer) Measures cover over shallow rebar |
|---|---|---|
Locates top-mat rebar | Plus everything else | Its core strength |
Measures concrete cover accurately (shallow) | Good | Excellent at shallow depth |
Detects conduit and embedded services | Distinguishes from rebar | Sees only ferrous rebar response |
Detects post-tension cable / ducts | Maps tendon drape | Cannot — dangerous gap for coring |
Sees a second/deeper reinforcement mat | To antenna depth | Limited, top-mat focused |
Useful depth in concrete | ~30–45 cm at 1.6 GHz | Shallow only (cover range) |
Detects voids and honeycombing | ||
Measures slab thickness | ||
Safe to clear a core / cut location alone | The clearance standard | Blind to conduit & PT — never alone |
Speed for a pure cover survey | Fast | Fastest for cover-only |
Equipment cost / simplicity | More capable, more skill | Cheap, simple |
Yes Partial / depends No
When to choose which
Choose Cover meter is enough when…
- The only question is cover depth over the top rebar mat
- A durability/condition survey measuring cover across an element
- Quick spot-checks where nothing will be drilled
- Verifying as-built cover against spec on shallow bars
Choose GPR is required when…
- Clearing a core, cut, or anchor location before drilling
- Post-tensioned slabs — a cover meter can't see tendons
- Distinguishing rebar from conduit and other embeds
- Mapping deeper bars, a second mat, voids, or slab thickness
- Any job where hitting a non-rebar target ends in a strike
Quick answers
Frequently asked
What's the difference between GPR and a cover meter?
A cover meter (pachometer) induces a magnetic field that responds to ferrous rebar near the surface, giving a fast, accurate measurement of concrete cover over the top mat. GPR sends a radar pulse that reflects off anything with a contrasting dielectric — rebar, conduit, post-tension cable, voids, the back wall — building a full subsurface picture to real depth. The cover meter answers one narrow question cheaply; GPR answers the whole 'what's in this slab' question.
Can a cover meter clear a core location?
No — and relying on one for that is how strikes happen. A cover meter responds essentially only to ferrous rebar near the surface; it is blind to embedded conduit and, crucially, to post-tension cable, the most dangerous and expensive thing to cut. It also can't see deep enough on thicker elements. Clearing a core or cut location requires GPR (or radiography where the slab demands it), full stop.
Is a cover meter more accurate than GPR for cover depth?
For shallow cover over the top rebar mat, a cover meter is excellent and arguably the purpose-built tool — that's exactly what it's designed to measure. GPR also reports cover well, but its advantage is breadth (depth, second mats, non-rebar targets, voids) rather than beating a pachometer at its one specialty. If cover over shallow bars is genuinely all you need and nothing will be drilled, a cover meter is a fine, fast choice.
Why can't a cover meter see post-tension cable?
Because it works by magnetic induction tuned to the response of ferrous reinforcing bar near the surface — post-tension tendons (often in ducts, at depth, following a draped profile) don't present the same shallow ferrous signature it's built to read, so they don't reliably show. GPR, by contrast, reflects off the tendon and its duct and maps the drape. In a post-tensioned slab — standard in BC towers and parkades since the 1970s — that difference is the difference between a safe core and a severed tendon.
Do you ever use both together?
Occasionally — on a detailed condition survey, GPR maps the reinforcement and embeds while a cover meter adds fast, dense cover readings over the bars GPR has located. But for the common job — clearing a penetration — GPR alone (read by a skilled operator) is the standard, because it's the only one of the two that sees everything a drill could hit. We pick the tool to the question and never substitute a cover meter where clearance is the goal.
Which is right for my project?
If you're measuring cover on shallow rebar and drilling nothing, a cover meter is cheap and quick. If you're drilling, coring, or cutting — or the slab is post-tensioned, congested, or thick — you need GPR. The honest test: 'could the drill hit anything a cover meter can't see?' On almost any real penetration the answer is yes, which is why our concrete scanning leads with GPR. A five-minute call sorts your specific job.
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GPR vs X-Ray
GPR vs Impact Echo (Slab)
Concrete Scanning Cost
Not sure which option fits your situation?
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