How to Survey with a CAT and Genny — Checks, Signal Methods and the Sweep

A survey runs in a set order: check the kit, apply a signal to the services you want to trace, then sweep the ground methodically. Knowing that shape helps you judge what the job takes — and why it's a trained task. For the why and when, start with the cable avoidance guide; for what the tools are, see what a CAT and Genny is.

A full CAT and Genny training walkthrough — pre-use checks, the signal-application methods and the sweep. Source: Sygma Solutions Training (a UK training provider — not a kit seller). It shows the workflow this page describes; the competence still comes from doing the training, not watching it.

Before You Start — Checks and Tests

A survey begins before you scan anything. The routine is a short sequence of confidence checks: a visual inspection for damage and that the unit is within its service/calibration date; battery checks on both the CAT and the Genny (and if batteries need changing, that's done in a gas-free location); a function check that the CAT picks up the Genny at the expected distance; and a known-source test — passing the CAT in power mode over a known live cable to confirm it responds as it should.

The point of all of this is simple: a locator that isn't working, isn't calibrated, or isn't set up right will quietly tell you the ground is clear when it isn't. The checks are how you trust the result. The exact steps and how often you do each one follow the manufacturer's instructions and your training.

Applying a Signal with the Genny

The CAT's passive modes only find what's already radiating. To trace a specific pipe or cable reliably, you apply a signal to it with the Genny, then follow it in Genny mode. There are a few ways to do that, traded off by how much access you have:

• Direct connection — clip the Genny onto an accessible part of the service: a meter, a street-lighting column, an external tap, a hydrant. It's the most precise method. You test the point with a volt stick first, and you never remove casing to make a connection.
• Signal clamp — a clamp placed around an accessible cable or pipe, used where you can reach the line but can't connect to it directly. The jaws must be fully closed and the CAT kept a few metres away.
• Induction — the Genny sits on the ground above the assumed route and induces a signal without any contact. It's the least selective method, used after the others are exhausted, and needs the generator set well away from where you're tracing.

Whichever method, the Genny is earthed properly and set up away from the area you're marking, and the signal is confirmed before you trust it. These are the steps where technique matters most and where training earns its place — a signal applied or earthed badly gives misleading results.

The Sweep — Surveying the Ground

With the kit checked and a signal applied, the survey itself is methodical, not a quick wave-over. The recognised approach is to work the excavation or staking area from each of its four sides in turn: scan across the area, follow any signal you pick up across and out of the area, mark it, then move the Genny and repeat from the next side. Scanning from one direction only is how a line running across your approach gets missed.

You also scan in every mode the CAT offers — power, radio and Genny — and check for airborne signals that can mislead, before committing. For how this maps onto a marquee footprint specifically, see scanning a marquee site before you stake. And remember the limit that no sweep removes: plastic and rubber services carry no signal unless one is induced — covered in finding plastic and non-metallic pipes.

Calibration, Service and Records

Cable locators are typically on an annual service and calibration cycle, and many display the service-due date on the unit itself. Alongside that factory cycle sits the user routine — the daily and weekly checks above. Modern locators also log usage and can produce survey records, which matter where you need to demonstrate that cable avoidance was carried out. An out-of-calibration or unchecked locator is not something to rely on for a safety-critical decision.

Talk It Through

We're adding a CAT and Genny to the Hogan range for the crews who drive our stakes. If you want to talk through what's involved, or which kit suits how you work, get in touch — and pair it with proper training before you rely on it on site.

Email: hoganuk [at] hoganstakes.co.uk
Contact form: hoganstakes.co.uk/contact

Safety note — this is an overview, not training. Cable avoidance is safety-critical work. This guide describes the shape of a survey so buyers understand what the equipment requires; it does not qualify anyone to operate a cable locator. Follow the manufacturer's instructions, HSE HSG47, and your own competent-person and training requirements. If a location cannot be established as safe, do not break ground.

Background drawn from HSE HSG47 and publicly available CAT & Genny training material (Paragon, Sygma Solutions, Proper DIY). Used as reference; adapted for UK practice.