Since its inception in the 1960s, wildlife radio telemetry has become a valuable tool to track the movement and behavior of animals. This technique uses the transmission of radio signals to locate a transmitter attached to the animal of interest. It is often used to obtain location data on the animal's preferred habitat, home range, and to understand population dynamics.The different types of radio telemetry techniques include very high frequency (VHF) transmitters, global positioning system (GPS) tracking, and satellite tracking. Recent advances in technology have improved radio telemetry techniques by increasing the efficacy of data collection. However, studies involving radio telemetry should be reviewed in order to determine if newer techniques, such as collars that transmit the location to the operator via satellites, are actually required to accomplish the goals of the study.
The operator attaches a transmitter to an animal that gives off unique electromagnetic radio signals, which allows the animal to be located. Transmitters are available in a variety of forms and consist of an antenna, a power source, and the electronics required to produce a signal. Transmitters are chosen based on the behavior, size, and life history of the specific species being studied. In order to reduce the impact of the transmitter on the animal's behavior and quality of life, transmitters typically weigh no more than five percent of the animal's body weight.Unfortunately, the smaller the transmitter, the weaker and shorter-lived it is. Transmitters are often designed to fall off the animal at the conclusion of the study due to the unlikelihood of recapturing the tagged animals. Large animals require transmitters in the form of collars, which leave room for the animal to grow without falling off. Ear tag transmitters are commonly attached to the ear of large animals that have changing neck sizes. Lightweight, adhesive transmitters are glued to the backs of smaller animals, such as bats. Necklace packs are transmitters that fit around the neck of upland game birds. Subcutaneous transmitters are applied to aquatic animals, which allows them to freely navigate underwater. In some species of fish that have ceased feeding, transmitters are inserted inside the animals body cavity as a means to minimize the stress of tagging . Whip antennas are an omni-directional transmitter design that produces more signal over a greater distance. A harness loop antenna design, implemented for small birds, involves a transmitter being wrapped around the body.
The operator uses an antenna that is attached to a receiver, which is programmed to the transmitter's frequency, to pick up the electromagnetic signals given off by the transmitter affixed to the target animal.Receiver antennas may be hand-held or mounted on an object, and they are available in a variety of forms and functions. These antennas are also tuned to the proper frequency for the transmitter. The receiver produces a tone that increases in loudness or has a visual signal strength indicator that pulses as the operator approaches the transmitter. Omnidirectional antennas have no additional elements and are used to determine the presence or absence of a signal, not its exact location. Elements are added segments of an antenna to increase the range of detectability of the receiver. Adcock antennas consist of two elements and are used to locate the direction of the signal. Loop antennas are small and useful for locating low frequency transmitters. The Yagi antenna contains 3 or 4 elements and is a strong, directional antenna commonly used to determine the location of a transmitter. Antennas can also be affixed to towers. This allows the antenna to be positioned higher, avoiding interference from buildings and trees. Boat, aircraft, and vehicle-mounted antennas allow the operator to exploit a larger area while tracking.
Direct tracking and triangulation methods allow the operator to locate a tagged animal. Direct or VHF tracking involves using a directional antenna to follow the signal given off by the transmitter to the exact location of the tagged animal.The operator rotates the antenna until the loudest signal is found. The operator follows the signal, checking the direction of the signal frequently until he or she reaches the tagged animal. Triangulation is often used when an animal is on private or inaccessible property because it allows the operator to remotely determine the location of the tagged animal. The operator obtains three or more azimuths or bearings from locations around the signal and calculates the intersection of the azimuths to estimate the location of the transmitted animal. Global positioning tracking involves a receiver that picks up signals from satellites to determine the location of a transmitted animal over time. The GPS transmitter is attached to an animal and records the location of the animal on the device by estimating the time taken for radio signals from at least three satellites to travel to the GPS transmitter. The data is collected by recapturing the animal to remove the GPS transmitter or remotely downloading the data off the transmitter. These units are often heavier and shorter-lived than the ones used for VHF tracking. Global positioning tracking is useful for migrating animals because their locations can accurately be determined, regardless of the distance they are from the operator. Satellite tracking is similar to GPS tracking and allows animal movement to be tracked globally. This form of tracking is useful for remote or inaccessible areas. Many of these systems implement platform terminal transmitters (PTT) that send electromagnetic signals to Argos equipment found on satellites. The Argos receivers estimate the distance to the transmitter to determine its location. This data is received by the Argos data collection relay system. The PTT transmitters require larger batteries, causing them to be heavier than VHF transmitters. Satellite tracking is more accurate at locating larger animals that are more exposed to the sky, such as birds or animals living in prairies, open deserts, or savannas.
Wildlife radio telemetry has advanced the research opportunities available for studying animal populations. It can be applied to many areas of management and research to determine the habitat use of tagged animals, such as roost and foraging habitat preferences.Radio telemetry has been used to study the home range and movement of populations. Specific migratory routes and dispersal behavior can be followed through radio tracking. Survivorship is often monitored with radio telemetry by studying age and mortality rates.
It is important that any negative effects of attaching radio-transmitters to animals are reported to improve methods and reduce harm to individuals in future studies.
Telemetry is the collection of measurements or other data at remote points and their automatic transmission to receiving equipment for monitoring. The word is derived from the Greek roots tele, "remote", and metron, "measure". Systems that need external instructions and data to operate require the counterpart of telemetry, telecommand.
The Transit system, also known as NAVSAT or NNSS, was the first satellite navigation system to be used operationally. The system was primarily used by the U.S. Navy to provide accurate location information to its Polaris ballistic missile submarines, and it was also used as a navigation system by the Navy's surface ships, as well as for hydrographic survey and geodetic surveying. Transit provided continuous navigation satellite service from 1964, initially for Polaris submarines and later for civilian use as well.
Radio navigation or radionavigation is the application of radio frequencies to determine a position of an object on the Earth. Like radiolocation, it is a type of radiodetermination.
A radio direction finder (RDF) is a device for finding the direction, or bearing, to a radio source. The act of measuring the direction is known as radio direction finding or sometimes simply direction finding (DF). Using two or more measurements from different locations, the location of an unknown transmitter can be determined; alternately, using two or more measurements of known transmitters, the location of a vehicle can be determined. RDF is widely used as a radio navigation system, especially with boats and aircraft.
Automatic vehicle location is a means for automatically determining and transmitting the geographic location of a vehicle. This vehicle location data, from one or more vehicles, may then be collected by a vehicle tracking system to manage an overview of vehicle travel. As of 2017, GPS technology has reached the point of having the transmitting device be smaller than the size of a human thumb, able to run 6 months or more between battery charges, easy to communicate with smartphones — all for less than $20 USD.
Automatic Packet Reporting System (APRS) is an amateur radio-based system for real time digital communications of information of immediate value in the local area. Data can include object Global Positioning System (GPS) coordinates, weather station telemetry, text messages, announcements, queries, and other telemetry. APRS data can be displayed on a map, which can show stations, objects, tracks of moving objects, weather stations, search and rescue data, and direction finding data.
Direction finding (DF), or radio direction finding (RDF), is the measurement of the direction from which a received signal was transmitted. This can refer to radio or other forms of wireless communication, including radar signals detection and monitoring (ELINT/ESM). By combining the direction information from two or more suitably spaced receivers, the source of a transmission may be located via triangulation. Radio direction finding is used in the navigation of ships and aircraft, to locate emergency transmitters for search and rescue, for tracking wildlife, and to locate illegal or interfering transmitters. RDF was important in combating German threats during both the World War II Battle of Britain and the long running Battle of the Atlantic. In the former, the Air Ministry also used RDF to locate its own fighter groups and vector them to detected German raids.
Argos is a satellite-based system which collects, processes and disseminates environmental data from fixed and mobile platforms worldwide. What makes Argos unique is the ability to clearly geographically locate the source of the data anywhere on the Earth utilizing the Doppler effect.
Radiolocating is the process of finding the location of something through the use of radio waves. It generally refers to passive uses, particularly radar—as well as detecting buried cables, water mains, and other public utilities. It is similar to radionavigation, but radiolocation usually refers to passively finding a distant object rather than actively one's own position. Both are types of radiodetermination. Radiolocation is also used in real-time locating systems (RTLS) for tracking valuable assets.
Transmitter hunting, is an activity wherein participants use radio direction finding techniques to locate one or more radio transmitters hidden within a designated search area. This activity is most popular among amateur radio enthusiasts, and one organized sport variation is known as amateur radio direction finding.
Animal migration tracking is used in wildlife biology, conservation biology, ecology, and wildlife management to study animals' behavior in the wild. One of the first techniques was bird banding, placing passive ID tags on birds legs, to identify the bird in a future catch-and-release. Radio tracking involves attaching a small radio transmitter to the animal and following the signal with a RDF receiver. Sophisticated modern techniques use satellites to track tagged animals, and GPS tags which keep a log of the animal's location. One of the many goals of animal migration research has been to determine where the animals are going; however, researchers also want to know why they are going "there". Researchers not only look at the animals' migration but also what is between the migration endpoints to determine if a species is moving to new locations based on food density, a change in water temperature, or other stimulus, and the animal's ability to adapt to these changes. Migration tracking is a vital tool in efforts to control the impact of human civilization on populations of wild animals, and prevent or mitigate the ongoing extinction of endangered species.
Acoustic tags are small sound-emitting devices that allow the detection and/or remote tracking of organisms in aquatic ecosystems. Acoustic tags are commonly used to monitor the behavior of fish. Studies can be conducted in lakes, rivers, tributaries, estuaries or at sea. Acoustic tag technology allows researchers to obtain locational data of tagged fish: depending on tag and receiver array configurations, researchers can receive simple presence/absence data, 2D positional data, or even 3D fish tracks in real-time with sub-meter resolution.
GPS wildlife tracking is a process whereby biologists, scientific researchers or conservation agencies can remotely observe relatively fine-scale movement or migratory patterns in a free-ranging wild animal using the Global Positioning System and optional environmental sensors or automated data-retrieval technologies such as Argos satellite uplink, mobile data telephony or GPRS and a range of analytical software tools.
In navigation, a radio beacon is a kind of beacon, a device that marks a fixed location and allows direction-finding equipment to find relative bearing. Radio beacons transmit a radio signal that is picked up by radio direction-finding systems on ships, aircraft and vehicles to determine the direction to the beacon.
Global Navigation Satellite System (GNSS) receivers, using the GPS, GLONASS, Galileo or BeiDou system, are used in many applications. The first systems were developed in the 20th century, mainly to help military personnel find their way, but location awareness soon found many civilian applications.
Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connected to an antenna which radiates the waves, and received by a radio receiver connected to another antenna. Radio is very widely used in modern technology, in radio communication, radar, radio navigation, remote control, remote sensing and other applications.
Formation Autonomy Spacecraft with Thrust, Relnav, Attitude and Crosslink is a pair of nanosatellites developed and built by students at The University of Texas at Austin. The project is part of a program sponsored by the Air Force Research Laboratory (AFRL), whose goal is to lead the development of affordable space technology. The FASTRAC mission will specifically investigate technologies that facilitate the operation of multiple satellites in formation. These enabling technologies include relative navigation, cross-link communications, attitude determination, and thrust. Due to the high cost of lifting mass into orbit, there is a strong initiative to miniaturize the overall weight of spacecraft. The utilization of formations of satellites, in place of large single satellites, reduces the risk of single point failure and allows for the use of low-cost hardware.
Pop-up satellite archival tags (PSATs) that use the Argos system, which is managed by CLS in Toulouse, France and CLS America in Lanham, Maryland, US, are used to track movements of marine animals. A PSAT is an archival tag that is equipped with a means to transmit the collected data via the Argos satellite system. Though the data are physically stored on the tag, its major advantage is that it does not have to be physically retrieved like an archival tag for the data to be available making it a viable, fishery independent tool for animal behavior and migration studies. They have been used to track movements of ocean sunfish, marlin, blue sharks, bluefin tuna, swordfish and sea turtles to name a few species. Location, depth, temperature, oxygen levels, and body movement data are used to answer questions about migratory patterns, seasonal feeding movements, daily habits, and survival after catch and release, for examples.
The Unified S-band (USB) system is a tracking and communication system developed for the Apollo program by NASA and the Jet Propulsion Laboratory (JPL). It operated in the S band portion of the microwave spectrum, unifying voice communications, television, telemetry, command, tracking and ranging into a single system to save size and weight and simplify operations. The USB ground network was managed by the Goddard Space Flight Center (GSFC). Commercial contractors included Collins Radio, Blaw-Knox, Motorola and Energy Systems.
The history of wildlife tracking technology involves the evolution of technologies that have been used to monitor, track, and locate many different types of wildlife. Many individuals have an interest in tracking wildlife, including biologists, scientific researchers, and conservationists. Biotelemetry is "the instrumental technique for gaining and transmitting information from a living organism and its environment to a remote observer".