What Is an HDD Locator and Why Is It Important?

About 1.2 million miles of pipes run under American soil to supply drinking water. Around, besides, over, and under them, you’ll find gas lines, fiber optic cable, and electric lines.

It’s a bit crowded down there these days. Any utility company or housing developer has to dig with care to install or replace pipes and cables to ensure they don’t hit any existing ones.

Guiding the drill head with precision is an HDD locator's job, which looks a bit like a metal detector on steroids. The locator tracks the drill bit to ensure it follows a planned path that avoids hitting any other conduits underground.

Let’s look at how an HDD locator works and its important role in horizontal directional drilling projects today. To help you with drilling terminology and expressions, read our Directional Drilling Glossary and Terminology.

How an HDD Locator Works

Horizontal directional drilling is a way of installing pipes, cables, and conduits underground along a planned path to not impact the surrounding area much. It’s a type of trenchless technology that allows you to avoid digging up the ground to put the pipe in.

It’s commonly used to install underground utilities, and an HDD locater serves as an electronic tracking and guidance system to ensure you dig where you mean to.

The locator is part of the first phase of a dig, where a small pilot hole is drilled from one surface point to another. That small hole is later enlarged to your pipe's size, which is then pulled through the hole. You can install a continuous piece of pipe that only disturbs the surface in two places, saving time and is more environmentally friendly.

By using a locating system, you can speed up the amount of time needed for a dig. You end up spending most of the time for a dig in the planning process rather than digging.

Parts of an HDD Locator System

Regardless of type, nearly every HDD locating system consists of three parts — transmitter, receiver, and display. Each variety's abilities and complexity are key parts of choosing the right one for a particular job.

Transmitter

Located just behind the drill head, a sonde transmitter is a slender tube about 15 inches long that collects and relays location information. Knowing the data strength and signal strength allows the operator to calculate the drill bit's clock position — which way it is pointing — the depth of the bit in the bore.

There are different types of transmitters to deal with different types of interference, like rebar or power lines. These days, most can also offer different signal strengths to provide more accuracy at deep depths and frequency options.

The nature of HDD work means transmitters tend to be a part that breaks and needs replacing or repairing. You want to check your housing regularly to ensure it’s providing adequate protection for the transmitter. If you start having problems like no data coming back, overheating, loss of pressure, or visible damage, it’s time to fix or change the transmitter.

Repairing a transmitter can take as long as 10 days, so you might consider replacement to avoid expensive downtime. A refurbished or used transmitter can reduce costs and makes an affordable option to have on hand as a backup during a job.

Receiver

A receiver is a handheld unit that receives the data the transmitter sends. The operator — sometimes called the locator — holds the unit near the drill head's bore location. The receiver is moved along with the head and transmitter to gather real-time location information continuously.

Display

The receiver's screen is the display, which shows the data the receiver gets from the transmitter. It allows the operator to see the drill's location and orientation to know if things are going according to the bore plan.

The operator can use the display to make adjustments to the drill head's pitch, direction, and depth to correct any drift from the planned path.

Types of HDD Locators

With the drilling head deep underground, you need a locator of some type, and there are three basic kinds to choose from. Which one you need is based on what is right for a particular job. The tech ranges from basic to advanced, allowing for differences in how deep and far you can dig and still communicate with the drill head.

Walk-Over

The sonde transmitter behind the bore head registers the angle, rotation, direction, and temperature. It sends the information through the ground to the surface, where this type of locator picks it up. The receiver is manually positioned over the sonde to decode the signal and send steering directions to the drill operator.

You’ll find this type of job that uses smaller drill rigs, which is the majority. Because it uses an electromagnetic signal to relay data, it’s best in locations where there aren’t many obstructions to block the signal.

Walk-overs are efficient for shallow bores and easy to set up. The more advanced versions give you real-time remote guidance and can work on multiple frequencies. However, they are limited by the depth at which you can dig and the amount of interference they can overcome.

Wire-Line

This magnetic guidance system uses wire grids laid on the ground surface. Information comes through the wire-line fitted with a drill string to verify the location of the drill.

These are best when there are significant interference issues in an area because it uses wire to transmit data. You’re able to monitor the HDD drill head from a greater distance and confirm its exact position underground, which gives you high accuracy when locating and steering.

This type of locating system is more costly and time-consuming to implement, so its value comes down to factors like the location of your job site, length of the project, and soil conditions.

Gyro-Based

This locator type gives you one of the most accurate readings because it is not susceptible to magnetic interference. It works well over long distances, but it is sensitive and prone to drift.

It’s a good choice to have at least 600 feet of clearance and need to cover a long distance with your bore. It’s more costly and not appropriate for the majority of jobs but perfect for certain types.

Track Your Drill Head With an HDD Locator

A locating system is a serious investment, but one pays off through improved efficiency and targeting on a job. Being able to guide and position the drill head allows your drill operator to keep the hole running along your planned bore path to keep a project moving.

If you’re interested in learning more about locating systems or need to replace parts of your current system, contact us to get the best parts match. Our catalog of refurbished sonde transmitters includes models for DigiTrak and Subsite systems, each backed by our 180-day warranty.