Airborne (aerial) animal or fish tracking in a single-engine Cessna can be a gut-wrenching, if not scenic, experience. But as a researcher, you may be faced with a project in which the best, maybe only way to collect your data, is via low and slow flying aircraft. It's more expensive than ground tracking, and an order of magnitude more dangerous. Aerial tracking can be utilized to track from one to hundreds of animals, terrestrial or aquatic, but usually is beneficial when tracking long-ranged animals, or fish in inaccessible river locations.

At ATS, we have Biologist Consultants on staff who are experienced in aerial tracking. They know the equipment requirements and are familiar with aerial tracking procedures. Make sure to tap their expertise whether this will be your first or fiftieth aerial tracking flight.

Tracking in an aircraft is performed essentially just as homing is on the ground, except that the tracking equipment is loaded into and mounted on small aircraft. Either fixed or rotary-wing aircraft can be employed for aerial tracking. Normally, a yagi-type directional antenna like ATS' Model 138XX Series 4 Element Yagi Antenna is used for aerial tracking. The antennas are mounted onto the wing strut on either or both sides of a high wing single-engine aircraft, such as a Cessna or Helio-Courier (chartering a helicopter is typically triple the hourly operating cost of fixed-wing aircraft). The antennas should be mounted on the aircrafts wing strut, pointing at an angle of about 15-30 degrees beneath the horizon, and about 25-40 cm forward of the aircraft's wing edge. Antenna mounting kits are available from ATS, Model 14114. The aircraft operator should check with the local FAA Flight Standards District Office to insure approval of the antenna and appurtenances.

The antennas are connected to a scanning receiver, such as the ATS R4500 series Scientific Receiver. If a dual antenna configuration is used, a 2-way antenna switching box is used, such as the Model 14115, which is available from ATS. The switching box is installed between the antennas and the receiver. The tracker monitors the receiver using a headset plugged into the receiver's phone jack. He also directs the pilot as to the direction he wishes the aircraft to proceed.

Just as there are a number of different antenna configurations used on the ground, so too in aerial tracking. The methodologies used will differ depending on the particular species being tracked and the objectives of the study. For more details, a paper "Choosing an Antenna for Animal Tracking" is available on this site.

If multiple individuals are being tracked in an area, the R4500 can be set to automatically scan multiple frequencies. Usually a dwell time of 0.5 to 2 seconds is used, i.e. each frequency is "listened to" by the receiver for a very short time, before moving on to the next frequency in the scanning table (a list of frequencies that are to be monitored, or scanned, by the receiver). This allows the researcher to track many targets over a short period of time. If aerial tracking will take place in different geographic locations, the R4500 allows for up to four frequency scanning tables to be stored in its memory. The researcher can easily switch to the appropriate table when changing locations or if tracking specific animal populations.

Now we'll examine a basic tracking scenario in which we want to locate an individual animal, such as a deer, elk, or similar species. Usually the researcher will have some knowledge of approximately where the animal is located. Assuming we are using high wing aircraft with side-looking antennas installed (forward-looking antenna configurations are more easily mounted on a helicopter), the first step is to direct the pilot to fly in the direction the animal is believed to be. Aircraft altitude will usually be between 600-2000 ft. above ground level. One of the advantages of aerial tracking is the increased signal range; as a rule, the higher you are in the aircraft, up to about 3000 feet, the better the range. Also, the problems associated with signal attenuation near the ground are minimized (since VHF

waves are line-of-sight, anything between your antenna and an animals transmitter, such as vegetation and brush, or a rise in contour, will "deflect" and weaken the signal.

Here is where the antenna switching box comes in. You'll want to have the switch in the "both" position until a signal from the tagged animal is heard. Now, you'll need to determine from which side of the aircraft the signal is strongest, by momentarily switching the antennas between left and right, and closely listening for the differences in volume level. Ask the pilot to turn 90 degrees in the direction you've determined the strongest signal is coming from. Once established on the new heading, you can then switch back to "both" antenna inputs going to the receiver, and repeat the process. As you home in more closely on the animal's signal, you can begin circling maneuvers of 360 degrees, turning in the direction of highest signal strength. You can again use the switching method of left, right, left, right, in short successive intervals to determine whether the signal is coming from within, or outside of, the circle you are tracking.

Pay careful attention to ground reference points like streams, trees, etc. even if GPS equipped, in order to help direct the pilot. In some cases, as when tracking waterfowl or other nesting birds, a tracker may require a ground tracking crew in order to precisely and visually locate the individual, since the aircraft can only get so low and remain safe. Two-way radio can be used by the aerial tracker to relay approximate position of the animal to the ground crew, who can than pinpoint position.

The most important aspect of aerial tracking work to consider is safety. When choosing a charter provider, aircraft, and pilot, do the necessary homework. Although closely regulated by the FAA, all operators are not alike. Make sure to carefully check an operator's references. The operator should have on staff a pilot who is experienced in animal tracking operations. Take the time to discuss all aspects of the flight with the pilot before boarding the aircraft. The benefit of aerial tracking is it allows operations in remote, uninhabited country; be sure to plan for and include survival gear appropriate for the operation.

If your work will include aerial tracking operations, you can learn more about it from a paper entitled "Procedure for the Use of Aircraft in Wildlife Biotelemetry Studies" , available here on our site. Then, give one of the experienced trackers at ATS a call to discuss your project further.

Copyright © 2005 Advanced Telemetry Systems, Inc.