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THE eBee UNMANNED AERIAL VEHICLE In May 2015, McIntosh Perry and UKKO agreed to perform a comprehensive test to compare the accuracies, timing and cost of an aerial survey performed by UKKO’s eBee RTK fixed wing UAV with the more conventional ground RTK GPS topographic survey completed in 2014. The eBee RTK flying wing carries an on-board Sony 18 Megapixel camera and operates much like conventional aerial photography platforms, with two notable differences: the eBee is an unmanned aircraft weighing only 850 grams, and the on-board camera is an inexpensive point-and-shoot camera. The eBee achieves its high photo resolution by flying at altitudes of less than 120 metres, where 1 pixel on the photograph is equivalent to 3 cm on the ground. The light weight and strong safety profile of this aircraft can exempt it under specific conditions from Transport Canada regulations which would otherwise require acquisition of a Special Flight Operating Certificate (SFOC) for each flight. The UAV is controlled by software called eMotion2, which allows the operator to use a laptop in the field to prepare the flight plan, monitor the aircraft’s exact position at all times, and control the unit while in the air. The software also acts as an interface between the UAV and the GPS base station. THE eBee AERIAL SURVEY A Trimble R10 RTK GPS unit set on a point with known coordinates was used as the base station for this survey. The GPS unit was provided by Cansel to use specifically for this test. The known latitude, longitude and ellipsoid height for the base were entered through the eMotion software on the laptop controller, and the base was connected to the UAV through the laptop, where real time RTK corrections could be pushed to the UAV during the flight. The onboard RTK GPS receiver in the aircraft constantly updated the laptop with the calculated deviation of its ‘fix’ from the base station, a value which averaged <2 cm throughout the flight. For accuracy comparisons, McIntosh Perry had previously set 6 targeted ground control points (GCP). These GCPs were not used in processing the final data, but only as a check on the accuracy of the positioning determined by processing the data acquired by the UAV. The mission plan was entered into the laptop; the photo- graphs would be taken with a lateral overlap of 70% and a longitudinal overlap of 85%. The maximum altitude for the mission was 100 metres, providing a ground resolution of 3cm/pixel. Setup required about 10 minutes. The eBee was hand-launched and flew a predetermined pattern of flight lines as preprogrammed in the mission plan- ning software, acquiring 314 photographs in just over 28 minutes. During the mission, winds peaked at 18 km/hour, and the UAV was able to adjust its track using the onboard RTK GPS unit and its attitude (correcting for yaw, pitch and roll) using the on-board accelerometer. The proximity to the airport required the operator to be aware of air traffic at all times, both visually and with the use of a radio tuned to the advisory frequency of the airport. The Ontario Professional Surveyor, Summer 2015 Flight Lines and Photo-Centres UAV was diverted on one occasion to ensure good separation from an aircraft climbing out on the aerodrome circuit. The diversion instruction to the UAV was performed quickly, the UAV moved to a ‘hold and orbit’ location, and the survey resumed as soon as the airspace was clear. RESULTS The post-processing software supplied with this unit, known as PostFlight Terra 3D, provides the aerotriangulation function for the photographs, configures the coordinate system to the one used in the original topographic ground survey (in this case NAD83CSRS MTM Zone 9), and the adjustment of the geoid separation of the base to orthometric elevations. Surface Model cont’d on page 18 17