Last month, we covered the basics of RC telemetry systems – including how they work and why they're useful. Despite the apparent benefits, telemetry is not for every modeler or every RC aircraft. In fact, many hobbyists feel that only large, high-dollar models warrant the expense and added complexity of telemetry components. That opinion is debatable, but there are alternatives for those who would like the benefits of in-flight performance data without the overhead of telemetry. One way is to use a GPS recorder.
There are numerous GPS recording devices available, and many are tailored for the demands of specific activities such as hiking or driving. The Hobbico Big 5 GPS Meter ($90) is intended for use in RC airplanes. It collects time, location, altitude (present and peak values), and speed (present/average/peak) data. Following a flight, you can scroll to read selected parameters on the Big 5's LCD screen. Or, you can upload the data to a computer and plot out the entire flight on Google Earth.
The Big 5 unit measures 2.56" x 1.57" x 0.82" (65mm x 40mm x 21mm) and weighs 1.4 ounces (40 gr). To invoke a common yardstick, it is very nearly the same physical size as a GoPro Hero 3 (but lighter). This size and weight make the Big 5 unit compatible with a wide array of RC airplanes. I'd say that most models weighing at least 12 ounces are fair game.
Power for the Big 5 comes from a built in 200mAh LiPo battery that is recharged via USB. You can expect up to 150 minutes of operating time. This is adequate for any RC application that I can think of. It may fall short, however, if you want to repurpose the Big 5 for something else, such as a long bike ride. In any event, you can operate the unit with external power via the USB port or the 3-pin RC-style plug.
Up to six hours of data can be saved to the built-in flash memory. There is no provision to expand the storage capacity.
This GPS unit can be attached to your model using whatever method you like. I use self-adhesive Velcro. The prime consideration when mounting the device is to avoid placing it such that electrically conductive material (metals, carbon fiber) are blocking the signal path up to the orbiting GPS satellites. You will also want to ensure that the Big 5 does not upset the model's center of gravity.