Radio Frequency Identification (RFID) is a wireless identification system able automatically to uniquely track, identify and locate individual particles. RFID systems contain three basic components: transponder (RF tag), antenna and transceiver (Figure 1). Data is generated and stored by a host computer. Often the antenna and the transceiver are packaged together as a ‘reader’. The RF tag houses an integrated circuit on which all information is stored. When the reader moves within operating range of the RF tag this detects an activation signal emitted by the antenna and starts transmitting information encoded in its integrated circuit. The reader decodes the information, which is passed to the host computer for processing. Basically an RFID tag can be attached to any ‘particle’ be this a tray of apples, an animal, vehicle, person or survey marker. The particle may move or have a fixed position. Today RF tags have been implemented in applications as diverse as cargo tracking, paying for petrol, retail, animal identification and toll-road access. RFID is also used for entrance checks on visitors to trade fairs such as the Intergeo.

RF tags may be active or passive. An active RF tag can contribute information to a process, such as machinery instructions, and contains a power supply. It also has read-write capabilities; these enable storage of information sent by the transceiver, greater memory capacity and larger operating range (up to 40 metres). Active tags are also bulkier (about the size of a coin) and more expensive than passive tags, and their lifespan is limited (up to ten years); to economise on power consumption they may operate at fixed intervals. Passive tags are generally read-only (similar to bar codes), have lower memory-storage capacity and their operating ranges vary from 2mm (ISO 14443) up to a few metres (ISO 18000-6) depending on the radio frequency. The incoming signal from the antenna provides just enough power to generate a response. Sized 0.15mm x 0.15mm and thin as paper (7.5 microns), they are virtually invisible (Figure 2).

RFID systems can operate at low frequency (30KHz to 500KHz) or high frequency (850MHz to 950MHz and 2.4GHz to 2.5GHz). High-frequency systems have high ranges and, with a response time of less than a hundred milliseconds, high scanning speeds. But they are expensive. Low-frequency systems pair short reading range and low scanning speed with lower cost. Because passive tags are cheap and have no battery they are produced in much higher quantities than active tags. High-volume production may reduce the cost of these tags to as little as €0.20 (US$0.25). As demand increases, the most likely scenario, these prices are expected to drop rapidly.

RFID technology has been around since the early 1920s. It was developed at MIT as a way for robots to ‘talk’ to one another. The technology was used extensively by the British in world war two as a way to track planes and other vehicles, the so-called Identify Friend or Foe (IFF) systems. The first trials of commercial applications began in the 1970s, but it was only in the late 1990s that RFID started to become available for widespread business use. RFID systems do not require direct contact or line-of-sight to operate well. Consistent results can be obtained under harsh environmental conditions, such as ice, snow, fog, paint and dirt. The new generation of readers has the ability to read multiple tags simultaneously.

Although RFID is a well-developed technology with a wide range of operational applications, introduction into the surveying arena has not yet got beyond the knock-on-the-door stage. Nevertheless, the potential geomatics applications of RFID technology are vast and diverse and include beacon-tracking and alternatives to physical markers. It may even be safe to say that future applications are almost limitless.