Burying RFID tags can prove challenging, because moisture in soil can absorb radio waves at higher frequencies, thereby preventing the tags from being read. What’s more, moisture can detune a tag’s antenna if that tag is buried in wet soil.
But it is possible.
The U.S. Federal Aviation Administration (FAA) has buried more than 1,000 RFID-enabled marker balls around a new runway at the Hartsfield-Jackson Atlanta International Airport. The marker balls, supplied by 3M’s Communication Markets Division, allow the FAA, airport employees and contractors to use handheld RFID interrogators to locate utility cables and pipes buried 5 feet underground, as well as determine the type of infrastructure they represent, and who owns that infrastructure.
3M’s Dynatel 2200MiD Series Locating and Marking system employs 4-inch-wide, high-density polyethylene plastic marker balls, each containing a coil antenna and a passive RFID transponder floating in a liquid combining water and biodegradable propylene glycol. This ensures that the liquid does not freeze. Since the RFID tag floats, it can automatically align itself in the best orientation for receiving and transmitting RF signals. The RFID chip’s 256-bit memory includes the ball’s unique serial number, and also allows users to program additional data onto the chip. The FAA is utilizing that feature to program each marker ball with details regarding which type of cable is located at which particular spot, as well as whose cable it is and whether it is composed of fiber, copper or another material. The ball can be positioned up to 5 feet underground. The FAA deployed the marker balls approximately every 200 feet along cables—every 10 feet in more congested areas—with multiple cables in close proximity, or with cable bends.
This is the only off-the-shelf system of which I am aware that is designed for tracking buried cables and pipes. If our readers are aware of any other solutions, please post information about them below.
—Mark Roberti, Founder and Editor, RFID Journal
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