If a radio frequency identification device were installed on items located underground, at what depth could they be reasonably pinpointed?
3M offers an RFID-enabled solution for locating underground pipes and cables. The company reports that its Dynatel 2500 series can identify tags buried from 3 feet to 8 feet deep (see 3M Upgrades Dynatel Locators)
Berntsen International, a Madison, Wisc., manufacturer and supplier of survey and utility markers, as well as related accessories, has also developed an RFID system for tracking pipes. The firm reports that its tags can be read at about 2.5 feet underground (see RFID Helps Prevent Sewer Disasters).
And RYB, a utility piping and networks firm, developed an RFID system for tracking buried polyethylene pipes. The solution not only allows for the detection of pipes underground, but also enables users to write data to the tags in or on the pipes, at a distance of up to 1.5 meters (4.9 feet). It consists of RFID marker tags that can be attached to pipes already installed underground. In the future, RYB plans to offer a variety of dimensions of its own PE pipes with built-in RFID tags (see GDF Suez Tries RFID Underground).
One thing to remember is that it is not always necessary to place a tag directly on an object. You could bury an RFID marker 3 feet deep and put information on the tag indicating the type of pipe below that tag, as well as how far beneath the tag it is buried. In other words, data on the tag could reveal that a sewer pipe made of polyethylene was buried 8 feet below the tag, or 11 feet from the surface.
The Taiwanese city of Taipei is burying its manhole covers and fitting each cover with a passive UHF tag so that later on, utility workers can locate any manholes they need to access. EPC Solutions Taiwan, the company that provided the RFID solution, says that a worker with the handheld and specially designed wand antenna can interrogate tags at a depth up to 60 centimeters (see Taipei Buries Its Manhole Covers).
—Mark Roberti, Founder and Editor, RFID Journal
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