EM Line Locating · Power · radio frequency
Passive Sweep Locating by EM.
Sweep an area for the signals buried metal already carries — live power at 50/60 Hz and re-radiated radio energy — to catch energised and conductive lines before a dig, without connecting to anything. The fast first pass that makes sure nothing live gets missed.
Free phone consult · No pressure · Mon–Sat 8am–6pm PT
Best suited for
Why it's used
- No access point needed — detects what's already broadcasting
- Power mode flags the most dangerous lines first
- Fast area coverage as the locate's opening move
- Pairs with active + GPR to close the gaps it can't
How it works
- 1
Power-mode sweep
The receiver is set to 50/60 Hz and swept across the area — energised power cables and any metal carrying stray power current announce themselves first, because they're the lines you least want to find with a shovel.
- 2
Radio-mode sweep
Switching to the radio band catches long conductive lines re-radiating ambient radio energy — adding pipes and cables that aren't energised but are still detectable passively.
- 3
Flag the field
Everything the passive sweep finds is flagged. Passive can't identify which line is which, so flags mark presence, not identity — the cue for where active tracing and GPR go next.
- 4
Hand off to active + GPR
Active locating then traces each known target precisely and GPR images the non-conductive lines passive can't see. Passive opens the locate; it never closes it alone.
Frequently asked
Why run a passive sweep if it can't identify lines?
Because its job is safety-first discovery, not identification. The power-mode sweep flags energised cables — the highest-consequence strike risk — before anyone applies a signal or breaks ground, and the radio sweep catches conductive lines you didn't know were there. It's the fast opening pass that tells the active-locating and GPR work where to concentrate.
Does passive locating find plastic pipe?
No — passive detection needs the line to carry or re-radiate a signal, and bare plastic carries nothing. Plastic water mains, PVC/clay sewer, and similar non-conductive utilities are invisible to every EM mode; they're found by GPR imaging or by tracing a tracer wire or sonde. A passive 'all clear' is never a real all-clear on its own, which is exactly why we never stop there.
Can passive locating miss an energised cable?
It can, if the cable is carrying little or no current at that moment, is shielded, or runs deep — which is precisely why a responsible locate doesn't rely on passive alone. Active tracing of known power feeds, GPR imaging, and (before any dig) hand-exposure or vacuum potholing at the dig point are the layers that turn 'probably clear' into 'safe to excavate'.
Is passive locating enough for a small backyard dig?
It's a start, not a finish. Even a fence-post or deck-footing dig deserves at least a passive power sweep plus active tracing of the known services and a GPR pass — because the cost of a passive-only miss (a struck gas or power line) dwarfs the cost of a proper locate. For pros and homeowners alike, the dual-method clearance survey is the right small-job answer.
Related EM methods
Active EM Line Locating
Apply a known frequency to a target line and trace only that line — the precise, unambiguous core of electromagnetic locating. Direct connection or signal clamp puts a traceable signal on a specific conductive utility so it stands out from everything else in the ground.
ViewInductive EM Locating
When there's no valve, riser, or bare conductor to connect to, the transmitter induces a locating signal into buried lines from the surface — letting a crew trace conductive utilities in areas where direct connection simply isn't available.
ViewEM + GPR Utility Clearance Survey
The complete pre-dig clearance: passive sweep, active EM tracing of every conductive line, GPR imaging for non-conductive lines and confirmation, sonde tracing for drains, and depths at the dig point. The single survey that makes breaking ground safe — and the everyday private locate done right.
ViewDepth Estimation & Utility Mapping
Add the third dimension and a permanent record: estimated burial depth at every point of interest, and a marked, measured map of what's underground — the deliverable that turns a one-day locate into a lasting site asset.
View← EM line locating hub·For contractors & pros·Utility locating applications·GPR services
Passive EM Sweep Locating across BC
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