Radio frequency identification is a short-range identification and tracking technology. There are two basic types of RFID: passive and active. Passive tags receive energy from an interrogator and reflect back a signal, whereas active tags have a power source (usually a battery) and broadcast a signal. Active tags have a longer read range—up to 1,000 feet or so. Passive tags, because they have no power source, have a shorter read range—usually within 20 to 30 feet, though some systems can read passive tags at longer range.
Given these limitations, it would be difficult to track cattle in a large open field. It would be better to track the animals as they move though a gate into the field. GPS is far better for tracking over large spaces. Companies such as Identec Solutions and Numerex have introduced tags with dual RFID-GPS capability. These tend to be expensive, however, which means they might be fine on a cargo container holding $1 million worth of luxury goods, but a little pricy for tracking cattle or goats (depending on the number of animals you want to track, of course).
I think the best solution is to set up chokepoints and identify the animals as they pass through these areas. I don’t think RFID will work to simply indicate an animal’s location over many acres.
—Mark Roberti, Editor, RFID Journal
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