Low-cost thermal and panoramic imaging systems for drone-based architectural surveys

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As well as the "Virtual Apartment" visualisation test bed we've been developing as our key input into the EPSRC-sponsored eViz project, with evaluations under way with our colleagues within the School of Psychology at the University of Plymouth, we've been looking at other technologies, particularly with regard to how we might capture basic environmental data from more complex sites that will support us in developing future Virtual Reality models and simulations. Over the past couple of months, we've been particularly interested in new portable and low-cost image capture technologies that might be capable of being flown on board small unmanned air vehicles (sUAVs) or "drones" as they are popularly referred to. Over the summer, we were lucky enough to acquire one of the new FLIR ONE thermal cameras, together with two of the latest Ricoh Theta spherical panoramic imaging systems.

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The FLIR ONE is an infra-red (IR) camera add-on for the iPhone 5 and 5s. Costing around £260, the performance of the FLIR ONE does not even come close to some of its more professional (and more expensive) counterparts, but the impressive feature of the camera is the way the system takes the output of the IR sensor (which has a resolution of only 80x 60 pixels) and combines it with the output of the visual camera (at 640 x 480 pixels). Using what FLIR calls Multi-Spectral Dynamic Imaging (or MSX blending), the system uses an edge and texture detection process to enhance the thermal picture in real-time (at a final resolution of 528 x 396 pixels).

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The Ricoh Theta camera is one of a new breed of devices stimulated by initiatives such as Google Street View. The camera uses a proprietary dual-lens "folded" optical system, in which a prism, located at the centre of the optics, channels incoming light to a pair of sensors. This means that the camera is capable of capturing spherical panoramic images of a scene and allowing those images to be manipulated in real-time (e.g. pan and zoom) using a bespoke and freely-downloadable viewing package. The 5-megapixel resolution is not as good as many mid-to-high-end Smartphones,but for proof-of-concept purposes, the images are acceptable. More recently,Ricoh has launched the M15 version of the Theta product (costing around £270), which adds an impressive (if rather grainy) spherical video capability, allowing clips of up to three minutes to be recorded.

Our first trial to assess how well these devices might stand up to being flown on board a hexacopter took place within the grounds of the School of Electronic, Electrical and Systems Engineering at the University of Birmingham. The hexacopter has been developed by one of our PhD students (and only reliable pilot!), Chris Bibb. Adhering to the usual safety standards associated with sUAV flying, we were able to capture some early panoramic and thermal images of the front of the School and were impressed with how they performed, even in the presence of considerable vibration of the hexacopter platform. The MSX blending certainly made all the difference to the images we captured - without that, it would have been impossible to associate the thermal images with the architectural features of the School building.

Our second and more recent trial took place on a very windy morning at the end of November 2014, at the Eden Project in Cornwall. Flying time was limited, as we had to take advantage of any lulls in the wind (the bowl-like topography of the Eden Project can generate some very interesting turbulence, even in light wind conditions!). We were also limited in the areas over which we could fly, and were under strict instructions to avoid the pens housing Santa's reindeers at all costs! On this occasion, we also flew the new Theta M15, in order to test the spherical video capability in flight. Again, both systems performed well, although this time, the FLIR ONE output suffered from considerable image "blooming", brought about by the effects of wind gusts on the stability of the hexacopter and the frequent exposure of the thermal sensor to large areas of sky. Images from our normal GoPro camera, which is gimbal-stabilised, were, however, fine. The results of this trial suggested that a second attempt should be made during periods of better weather and we are now looking to design a 3D-printed mounting for the FLIR ONE so that it, too, can be attached to an appropriate gimbal mechanism.

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Another aim of ours is to fly a small Geiger Counter as a precursor to a more in-depth PhD research project which will address how best to visualise data from this kind of sensor, fused with the output of others, including these described above and future models and variations. For early trials, we will be using a bGeigie Nano Geiger Counter and the project will be undertaken in collaboration with colleagues from the Birmingham Centre of Nuclear Education and Research. The original bGeigie device was developed by Safecast, an organisation that evolved following the March 112011 earthquake and Fukushima nuclear power plant incident in Japan, and as a result of securing start-up funds via pledges made during a Kickstarter crowd-funding initiative. The bGeige Nano is a powerful integrated radiation sensing system, consisting of a GPS receiver, a micro-SD card, data logger, Arduino microcontroller, OLED display, and Pancake Geiger Mueller tube with mica window, all housed within a small (14.9 x10.3 x 5.4 cm) waterproof Peli case. Our ultimate aim is to feed the fused sensory information into a virtual topographical (and geo-specific) model of the site under study for both real-time and offline data evaluation.

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Professor Bob Stone
Director

Human Interface Technologies Team
School of Electronic, Electrical and Systems Engineering
University of Birmingham
www.birmingham.ac.uk/stone