By Bill McNeil
Over the last several decades, great strides have been made with respect to camera and lens combinations, sensor technology and image processing software, yet, until recently, remote sensing has remained expensive and complex. Thanks to the confluence of three different technologies — inexpensive unmanned aerial vehicles, lightweight action cameras and powerful new photomosaic software — the process has gotten less expensive and easier to use.
Solo UAVs
For years, much of the data collected for remote sensing has been gathered from cameras or other sensing devices carried by expensive manned aircraft. Now, new drones from the likes of 3D Robotics, DJI and others can perform many of the same tasks at less than a third of the cost.
3DR’s Solo with a GoPro Camera
One of the many features of Solo is the ability to fly autonomously or “hands-free”. This is an invaluable tool for remote sensing because once an area to be mapped is selected, Solo computes the flight path and while in flight, onboard software automatically communicates with the GoPro camera, capturing and geotagging photos. The combination of HD streaming and autonomous flight means data processing for remote sensing can begin while Solo is still airborne.
An autonomous flight plan created by 3D Robotics UAV
The Solo gimbal with a GoPro Hero4 camera
GoPro is a U.S. corporation that develops, manufactures and sells small, high-definition, battery powered, lightweight, portable cameras often used to create action videos. Their waterproof cameras can take 12MP pictures at 30 frames per second and 240 frames per second slow motion video.
Although GoPros are extremely popular, they’ve had limited use in remote sensing applications because it wasn’t possible to access the camera controls remotely. In other words, you couldn’t take individual shots, start and stop recording, or change the settings during flight. Another issue was that the wide-angle view, created by the fisheye lens, distorted images and made them difficult to use for mapping or terrestrial 3D modeling.
GoPro’s latest cameras, the Hero3 and Hero4, now provide access to the controls via Wi-Fi and Bluetooth. Their Smart Remote technology also allows the control of multiple GoPro cameras from distances of up to 600 feet. Solo, through the use of their attached gimbal, is one of the first companies to access these controls. Without this capability it would be difficult for Solo, or any UAV, to collect useful data for remote sensing applications.
Pix4D processes terrestrial and aerial imagery
Despite the advances 3DR and GoPro bring to the industry, there is still one more component: data processing software. The images that are captured during an automated flight need to be processed into a photomosaic map. Think of it as a huge jigsaw puzzle with many pieces that don’t exactly fit. They don’t always fit because some images may have a slight oblique angle, vary by color, which is often caused by cloud shadows, have lens distortion, or some or all of the above.
Pix4D, based in Lausanne, Switzerland, has the problem figured out. TheirPix4Dmapper software is an elegant solution that automatically processes terrestrial and aerial imagery acquired by GoPro cameras. Not only can their application remove fisheye lens distortion, they can also process input from any lens or angle, and optionally include geotags and ground control points.
GoPro data processed by Pix4Dmapper can be used to measure volume extractions, generate contour lines and build precise maps and models for construction, cultural heritage or archaeology sites. The 3D images below are of a fountain created from GoPro data that were processed by Pix4Dmapper.
Together, 3DR’s Solo, GoPro cameras and Pix4Dmapper are making remote sensing easier and less costly, and as a result, more available for widespread use.
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