Twenty-five years ago, GPS technology began to be extended from military systems navigation to use in flight testing for aircraft attitude determination as well as civilian applications.

Jump ahead to today with the proliferation of microprocessor and computing power advances in consumer electronics, and GPS is almost a commodity feature.

One expanding use of the technology is in unmanned aircraft, or drones, both for commercial and recreational purposes. As a one-time flight test engineer, I looked forward to borrowing a Parrot Bebop drone to explore its operation and the technology behind it.

Out of the Box

Upon unpacking the Bebop, its simplicity of design is striking. The only moving parts are the four prop motors. The fixed 14 megapixel camera needs no moving gimbals to control it, which would add complexity, weight and be subject to damage from impacts. Instead, the image sensor field of view is wider than that recorded for video or low-resolution images. Electronic image stabilization algorithms maintain a stabilized recorded image within that field of view when the drone is subject to turbulence. The wide image sensor field also allows the recorded/imaged area to slew without having to tilt or pivot the drone itself.

Low-res image taken during a video recording. Image source: Rick DeMeisThe camera, GPS antenna and electronics are contained within a foam upper body that sits on a magnesium plate, which serves as a heat sink and "EMI shield," according to Parrot. The plate is connected by four flexible vibration dampers to a fiberglass-reinforced ABS plastic frame that supports the four brushless electric motors and landing legs. At the rear of the body shelf is the lithium polymer battery, the same type that powers the separate flight controller (Skycontroller). On the underside, a small imager tracks the ground at low altitude to determine speed. An ultrasound sensor determines altitude below 8m (26 ft); above that level a pressure sensor takes over.

Parrot engineers point to their proprietary chipset, system integration and software (image stabilization with anti-vibration algorithms) as the Bebop's technology enablers. Included is a single chip in the inertial measurement unit that contains the three-axis accelerometer and three-axis gyro for attitude control. In addition, a magnetometer serves as a heading reference to avoid heading drift and aid the return-to-home feature when activated.

Into the Air

Flying the Bebop is done by either a smartphone, tablet computer or the dedicated Skycontroller unit with twin joysticks. The company's Freeflight 3 app must first be downloaded onto the device used. This app provides the user with a pilot's eye view from the camera as well as system cues and settings.

(Downloads are also issued periodically to update firmware.) Even when using the Skycontroller (a $400 list-price purchase that is separate from the $499.99 list price of the Bebop), a phone or tablet with the app mounted to the controller can serve as an information and video display.

Vital to flying, relatively trouble free is first viewing several videos within the app or on YouTube for informative preflight briefings. (Also helpful may be Internet videos from various drone gurus, but these vary in quality and usefulness.) For initial flights, or when the drone is operating against a background darker than the sky, a person acting as a spotter can keep the vehicle in view and aid in avoiding obstacles, especially if the pilot is concentrating on the camera's view.

High-resolution, full-frame image with the fisheye lens. Image source: Rick DeMeisI tried using all three devices to evaluate their relative utility for controlling the drone. First off, control range with the phone and tablet is limited to roughly 300m (1,000 ft). The Skycontroller with large antennas can reach out to 2 km (1.25 miles). Of note are current U.S. Federal Aviation Administration rules for drone flying that require the vehicle be kept in view and below 400 ft altitude. With the Bebop's fairly compact size, if flown out to 2 km, it will not be visible without the aid of binoculars. In addition, its programmed altitude limit is 200m, nearly 650 ft.

Using an iPhone, I found the control was intermittent and not very precise. The former was probably exacerbated by the film over the touch screen, which makes up part of my phone's protective case. The latter came about from having large fingers on the relative small phone screen. Using a larger iPad without a protective film was an improvement, but using fingers on a screen still was not precise enough in controlling drone movement to my liking.

The two-stick Skycontroller is worth its cost, not just for added range, but also for precise, intuitive controllability. The left stick movements control altitude (stick up and down) and yaw rotation (stick left and right). The right stick governs flight direction (stick up, forward; stick down, backward; stick left and right, flight left and right).

Some of my first flights were indoors with a set of detachable protective bumpers the Bebop comes with for safeguarding objects, as well as the props. For outdoors, I first used these bumpers for prop protection, but found that they could act as sails. Indeed, the bumper-clad props were caught by the wind on a couple of flights when the drone cleared the height of some trees that were not all that close. Perhaps the turbulence streaming from the treeline was enough to overcome the flight control software and power, resulting in a tumble back to earth. Bumpers were never used again outdoors.

Up and Away

With several flights completed, control and imaging becomes relatively intuitive. The HD video (30 frames/sec) is extremely stable. The Bebop can be seen to hold position in the sky, but bounces around by air currents and turbulence. However, image stabilization produces an exceptionally smooth video—the only hint of any unwanted motion comes from the periodic appearance of a prop or sensor edge in the video, indicating drone movement around the constantly held image direction.

Recording in the video mode, it is possible to take still images, but these are low-res at only 0.5 MB. A separate higher-resolution still image mode takes 8 MB RAW images and a 1.5-2.0 JPEG image simultaneously. These files are circular fisheye images that require correction in image-editing software to avoid excessive distortion.

As for control utility, a “return home” button will take the Bebop up to 10m (30 ft), or it will remain at a higher altitude, and the vehicle will be GPS guided back to the initial takeoff point. A landing button brings the drone down for a smooth landing. (An emergency button stops the motors altogether, but results in the drone dropping to the ground.)

Image correction software allows removing lens distortion from full-frame images. Image source: Rick DeMeisWhat might be considered design shortcomings include the lack of an SD or microSD card slot to record and transfer image/video files. The Bebop uses a cable to download this information into a computer for permanent storage and manipulation. Configuration-wise, the camera lens is out front on the vehicle and susceptible to damage and scratches, as happened after a tumble. A replaceable lens protective cover glass or peel-off film would avoid permanent damage.

On one flight, the Parrot entered a left yaw at 30°- 40° per second and would not respond to yaw control inputs—so a landing was commanded. The next day, normal control returned, but when left in the sun on a hot day like the previous one, the problem returned. Placing the drone in the shade cured the fault. Parrot engineers said the problem was in the magnetometer that serves as a heading reference to avoid heading drift.

All in all, the Parrot Bebop is a good first drone that comes equipped with video and imaging that are a step above a beginner system.