Wildlife Radio Telemetry Methods

In this seminar students were able to use a receiver, antenna, compass, and GPS to get bearings to a radio transmitter collar from established locations. They learned two methods for deriving the coordinates of an animal’s location. They first used triangulation to establish the coordinates of a remote target from known locations and the second involved calculating the coordinates of the target if it could be approached.

Here OLC student/trainer Adam Heriba takes notes as Val Charging Eagle, Patty Apple, Gwen Foote, Jeff Laubach, and Lyle Iron Horn locate our radio collared “animal”, actually just a radio transmitter collar positioned in the field.

Sighting through their compasses down the line of the directional antenna, they establish a bearing from this position out to the transmitter.

From 3 such bearings and GPS coordinates for these locations, they will learn how to compute the coordinates of the collared animal. This technique is used if the study animal is not approachable, such as is the case with turkey, deer, and many other wildlife.

We also measure the distance and angle from a known point out to the transmitter and compute the new coordinates using simpler methods than those required for triangulation. We can use this technique when the animal is not disturbed by direct approach of the researcher, such as a turtle or flying squirrel.

Back in the lab, Adam shows the class how to go about doing the math to take our GPS coordinates for known locations and azimuths to the target animal, and use those to calculate the coordinates of the animal.

Then he demonstrates the simpler method of finding the new coordinates when we can use one known location and the azimuth and measured distance to the animal.

This seminar presented several concepts and methods used in zoological field research, use of the GPS, the various uses of the compass for orientation and mapping, use of a radio telemetry receiver and hand-held directional antenna, and calculations using geometry and trigonometry.

If you are interested in learning more about these field methods and computational techniques, contact me at jtaulman@olc.edu. I can provide you with diagrams of sample triangulations and spreadsheets with computational formulas for automatic calculations.

General telemetry procedures.

In field:

1. Take 3 azimuths at target beacon from different locations, capturing UTM location in meters of each telemetry origin point with GPS.

2. Estimate azimuths as nearly as possible using compass as antenna is pointed at target.

3. Plot these 3 azimuths on graph paper and estimate center of error triangle formed by intersection of azimuth lines.

4. Redo the 2 azimuths farthest apart, getting new azimuth from origin to new estimated target position. Use these 2 azimuths for further calculations.

Back in lab:

1. Calculate the hypotenuse of a right triangle drawn between origin locations, using legs between them, with Pythagorean theorem.

2. Get both acute angles of that right triangle using arcsin functions and known leg lengths.

3. Get both angles of main triangle between origins and target location using appropriate calculation depending on positions of origins and target.

4. Get angle of main triangle at target, 180º - the other angles.

5. Get leg distance of main triangle using formula A/sin a = B/sin b, with angles of main triangle and the one known leg length.

6. Make right triangle using new leg between one origin and target as hypotenuse, deriving other legs by sin and cos functions.

7. Add leg lengths of right triangle to origin x and y values to achieve new target coordinates.