New Zealand Certified Locator Program

The four key features of an EMF Locator:

  1. Manual Gain
  2. Separate Peak and Null
  3. A range of Frequencies
  4. Be able to read Current

These features are required to enable us to provide a reliable electronic location.

The four steps to a reliable location:

  1. Connect. Direct or clamp
  2. Confirm. Sweep, determine signal point and identify target by current
  3. Trace. Minimise gain adjustments and check Peak/Null
  4. Sanity Check. Trace to known end

AS-5488 Quality Levels:

  1. QL-A Verified Potholed +/- 50mm
  2. QL-B Reliable electronic location. 300mm Horizontal, 500mm Vertical
  3. QL-C Identify buried assets by surface features but not able to achieve QL-B
  4. QL-D Identify asset in the vicinity by plans but not able to achieve QL-B


  1. Gain must be manual, not automatic.
  2. Set to 50-60%
  3. When gain changes it is telling you something.
  4. Change of direction or depth.
  5. A split or tee in the target.

Peak / Null:

  1. Allows us to determine if we have a round signal or a distorted signal.
  2. Tells us if we can give an accurate depth.
  3. If Peak and Null do not align we have a distorted signal and should not give a depth.
  4. Allows us to determine true location of the target. Half the distance between the Peak and Null and transfer outside the Peak.
  5. ALWAYS check Peak and Null before placing a mark.

Signal Trace Frequencies:

  1. Low Frequency – Typically 8 kHz and lower - Low frequencies are best for Direct Connection.
  2. Medium Frequency – Typically 33kHz - Medium frequencies are best for Induction Method of Connection.
  3. High Frequency – Typically 65kHz and higher - High frequencies are best for Induction and the Inductive Clamping method of Connection.


  1. We read it in milli amps mA
  2. It is used to determine the target. Highest mA.
  3. Used to identify branch line or tees.
  4. We want to achieve Maximum current for best signal flow.

To increase CURRENT:

  1. Reduce resistance - e.g. water on earth stake, use bigger earth stake, connect bigger target (largest cable size)
  2. Increase voltage - Increase transmitter output

 Active Methods of Locating:

  1. Why? Because we apply the signal using the transmitter
  2. They are:
    1. Direct Connect
    2. Clamp
    3. Induction

Passive Methods of Locating:

  1. We use only the receiver
  2. We detect naturally occurring noise.
  3. We can only determine conductive assets
  4. We can not identify them.

Caution! Power Passive does not necessarily identify power cables.


Work to a process:

  1. Where is the job site
  2. Obtain DBYD (essential) and any other plans or anecdotal information
  3. Clarify work area with client
  4. Walk and inspect work area looking for signs of buried assets.
  5. Check all plans and prioritise them
  6. Locate everything you can to QL-B
  7. Identify that which is QL-D
  8. Complete active and passive sweeps
  9. Complete site report and go over with client

Plans are not 100% accurate:

  1. Never take plans as the truth. They are a guide.
  2. Always compare what the plan says to what you see and let your locator discover the truth.
  3. Open every pit.