What is a Magnetic Locator?

Magnetic locators are devices that are used to locate buried or hidden ferromagnetic objects. These devices are often confused for metal detectors, however, they operate very differently and can often outperform traditional metal detectors for some tasks. In this article, we will cover what magnetic locators are, how they work, and what they are used for.

For the purposes of this article, ferromagnetic items will be defined as any item that can become magnetized. This includes items made from iron, cast iron, steel, and stainless steel. The terms magnetic and ferromagnetic will be used interchangeably throughout the article.

How Do Magnetic Locators Work?

Each magnetic locator has two magnetic sensors. One near the handle and one near the tip. The sensor in the handle reads the magnetic field of the earth within the work area. This field is generally fairly weak and stable. The sensor near the tip reads the magnetic field of the ground in front of the operator.

If an iron or steel item is buried in the ground below the locator’s tip, it will have its own magnetic field as a result of magnetic induction from the Earth. When the locator detects a difference in fields read by the two sensors, it will alert the operator with audio or visual signals.

How Deep will a Magnetic Locator Detect?

Since magnetic locators work by detecting small variances in magnetic fields, they are extremely sensitive. This means that very small and very deep items can easily be detected. It also means that a skilled operator can use a magnetic locator to identify the size, shape, and depth of an item before beginning excavation. This allows operators to concentrate only on signals that match the expected target profile which in turn can prevent unnecessary digging.

The diagram below gives a rough estimate of depths at which a magnetic locator can find common ferromagnetic items under normal searching conditions. These depths can vary depending on soil type, soil moisture, ambient electromagnetic interference, operator skill, and the brand of magnetic locator.

What are Magnetic Locators Used for?

Magnetic locators are used in many industries for a variety of purposes. The list below contains a representative selection of fields where magnetic locators are used and descriptions of how professionals in those industries might use magnetic locators during the course of their jobs.

Magnetic Locators in the Utility Industries

Utility workers use magnetic locators to find underground pipelines, valves, septic tanks, and buried manhole covers. Although these devices will not work on pipelines made of plastic, ceramic, or concrete, those made of steel or cast iron can easily be located by a magnetic locator. On non-ferrous pipelines, the presence of steel valves or cast-iron pipe joints and fixtures can be used to locate unmarked pipelines.

Magnetic Locators on Construction Sites

Construction and demolition crews use magnetic locators when searching for rebar locations or steel structural beams that might be hidden in foundations or behind walls. They can also be used to locate nails and PK nails which may have been used to mark important reference points on architectural features.

Magnetic Locators in the Timber and Lumber Industries

Items such as nails and wire hidden inside tree trunks and timber pose a significant danger to lumberjacks, sawmill operators, and wildland firefighters. Workers in these industries can use magnetic locators to scan tree trunks before using a chainsaw to reduce the chance of kickback from hidden metal objects in the wood. At the lumber mill, magnetic locators can be used to identify logs with nails and wire before they are fed into the mill, reducing the chance of costly damage to the mill’s machinery.

Magnetic Locators in Unexploded Ordinance (UXO) Surveys

UXO operators are tasked with the identification and removal of unexploded military ordinance from battlefields and military training facilities. Magnetic locators are an essential tool for these workers as they perform UXO surveys. Some magnetic locators, such as the ML-3L by Subsurface Instruments, have been designed with extra-long shafts to put as much distance as possible between the UXO operator and the munitions that they are locating.

Magnetic Locators in Law Enforcement

Magnetic locators are ideal tools for members of law enforcement searching for hidden firearms or steel shell casings at crime scenes. Some locators such as the ML-3 by Subsurface Instruments are designed for underwater use and are perfect for police divers working to recover evidence that has been hidden in ponds and rivers.

Magnetic Locators for Surveying

Survey crews commonly use magnetic locators to find iron survey pins, PK nails, steel pipe corner markers, or old fence lines. Magnetic locators allow surveyors to locate these markers even in dense undergrowth or when they have become buried underground.

Is a Magnetic Locator Right for Your Project?

Magnetic location devices can be useful tools for a variety of location projects. If you are considering purchasing a magnetic location device, we encourage you to reach out to us through our Contact Us page. We will be glad to answer any questions you have and to help you find the magnetic locator that best fits your location needs.

If you would like to know more about magnetic locators, we have another article, The Ultimate Guide to Magnetic Locators that may be helpful.

-Precision Outdoor Tech.