# Positioning Methods and the Use of Location and Activity Data in Forests
## 2 Types of Positioning Technologies
### RFID and Acoustic Positioning  
RFID entails communication between an antenna and electronic tags via radio waves. Passive RFID, primarily used for tracking objects, can operate only at very close ranges of 1-3 m [5], whereas active RFID used for positioning has a much greater range of 15 m to 1 km (Table 1) [124; 125; 126; 127]. RFID tagging is of increasing interest in precision forest management for tracking forest products through the supply chain [124]. By monitoring individual logs, companies gain a greater understanding of the quality and quantity of wood being processed from diverse sources [128]. RFID systems also help document product chain of custody to support sustainable forestry certification [129]. RFID technology is an important component of biotelemetry, which has been used to study and monitor fish at multiple spatial and temporal scales for decades [96; 130; 131; 132; 133]. Trends in miniaturization and reduced prices have led to rapid increases in application, spatial extent, and number of telemetered fishes, which has resulted in big data needs for data transmission, management, and analytics. Three technologies are widely used in fish telemetry: (1) passive radio telemetry with passive integrated transponder (PIT) tags (Figure 8) [134], (2) active radio telemetry (i.e., radio tags), and (3) active acoustic telemetry with tags producing ultrasonic signals that propagate through water and are received by hydrophones [132]. PIT tags are \"passive\" because they do not require a battery [134; 135; 136]. Two separate PIT technologies have been applied in fish monitoring. Full-duplex (FDX) antennas produce an electromagnetic field with an antenna coil, which powers the tag directly to transmit a coded radio signal back to the PIT antenna, with simultaneous charging and listening by the antenna. Half-duplex (HDX) PIT antennas create a field that charges a capacitor in the tag, which then transmits a stronger signal back to the PIT antenna, which alternates between charge and listen modes. HDX PIT tags thus have longer read ranges but are larger. FDX systems simultaneously transmit and receive signals at up to 1800 Hz whereas HDX alternate between transmit and receive modes at up to about 840 Hz. Biotelemetry studies have addressed questions of fish behavior, movement and migration, energetics and stress response, estimation of mortality and survival rate, habitat use, response to angling, and monitoring of invasive species (see recent reviews in [PERSON] et al. [132], [PERSON] et al. [135], [PERSON] et al. [96], and [PERSON] et al. [133]). Aquatic studies are not limited to economically important fishes (e.g., [PERSON] et al. [137]) and have also included larger aquatic invertebrates (e.g., crayfish [138] and freshwater mussels [139; 140]). Integration of depth sensors, temperature sensors, and accelerometers to telemetry tags promises a new wave of detailed studies [96]. For instance, [PERSON] et al. used a prototype commercial radio tag with accelerometers to develop protocols to quantify spawning behavior in steelhead trout in turbid rivers during snow-melt runoff [141]. Radio-telemetry tags use an onboard battery to actively transmit identity, and in some tags, data on depth, temperature, acceleration, or other parameters. Range is typically greater than 1000 m when tags are near the surface of freshwaters, but effectively zero below 10 m [135]. Commercially available acoustic tags also use battery power to actively transmit identity and may also transmit other parameters such as depth. These can be used effectively in deep habitats such as lakes and slow rivers but are limited in rapidly flowing waters (i.e., those with entrained air). Monitoring is primarily accomplished by either fixed sites or mobile tracking for PIT tags and both types of active tags [132; 135]. Fixed sites for radio receivers may be on alternating current (AC) hard power, solar, or battery. Received data can be manually downloaded or transmitted via cellular or satellite networks.