Utilizing Unmanned Aircraft System (UAS) Technology without the need for Ground Control Points Mike Gilkey and Tom Hughes 3DAerial Solutions LLC 2015 Ohio GIS Conference September , 2015 | Hyatt Regency Columbus| Columbus, Ohio

Overview UAS technology effectively complements existing techniques, fitting between large-area satellite/manned aircraft imagery and smaller coverage, time-consuming, but highly accurate terrestrial approaches The standard senseFly eBee can achieve 3 cm Orthomosaic (horizontal) and 5 cm Digital Elevation Model (vertical) accuracy. This provides an expected level of accuracy of between 1-3x Ground Sample Distance (GSD), but requires use of Ground Control Points (GCPs) The senseFly eBee RTK can achieve 3 cm horizontal and 5 cm vertical accuracy with an expected level of accuracy of between 1-3x GSD without using GCPs 9/22/15Ohio GIS Conference 2

3D Aerial Solutions 3D Aerial is an Unmanned Aircraft System (UAS) technology company ▫ Based in Dayton, OH. We provide commercial UAS flying services with the eBee. ▫ Received FAA Section 333 exemption and blanket COA in March 2015 ▫ FAA aircraft registration complete in May 2015 ▫ Over 150 flights, > 37 flight hours since June We also provide UAS consulting services and are a sales representative for senseFly products. 9/22/15Ohio GIS Conference 3

senseFly eBee eBee ~1.5 pound take off weight 38 inch wingspan EPP foam and composite construction 160 W brushless DC motor ~50 minutes of flight mph cruise speed operates in winds up to 28 mph Radio link to 1.8 miles Sony WX 18.2 MP camera (others available) GSD: down to 0.6 inch DEM accuracy: ~1-3x GSD (with GCP) Accuracy (with GCP): 1.2 in (hort), 2.0 in (vert) Accuracy (no GCP): ft (hort & vert) 9/22/15Ohio GIS Conference 4

senseFly eBee RTK (Real Time Kinematic) eBee ~1.6 pound take off weight 38 inch wingspan EPP foam and composite construction 160 W brushless DC motor ~40 minutes of flight mph cruise speed operates in winds up to 28 mph Radio link to 1.8 miles Sony WX 18.2 MP camera (others available) L1/L2, GPS & GLONAS RTK receiver GSD: down to 0.6 inch DEM accuracy: ~1-3x GSD Accuracy (no GCP): 1.2 in (hort), 2.0 in (vert) 9/22/15Ohio GIS Conference 5

Bundled Software The eBee comes with the following software ▫ eMotion 2: Flight planning and control application for precision image collection  Produces geotagged images with selected resolution and overlap to support desired GIS products ▫ Postflight Terra 3D (Pix4D Product): Photogrammetry application to create 2-D orthomosaics and 3-D DSM  Outputs are compatible with most major GIS packages including erdas, ArcGIS, Global Mapper and Quantum GIS There are no additional subscription fees with either package and software updates are provided for the life of the product. 9/22/15Ohio GIS Conference 6

Postflight Terra 3D 9/22/15Ohio GIS Conference 7

Postflight Terra 3D 9/22/15Ohio GIS Conference 8

9/22/15Ohio GIS Conference 9 Process Flow Generate Products Pre-Mission Planning Pre-Flight Checklist Fly Mission Post Flight Checklist Data Merge Data Processing

3 Methods to use eBee RTK Virtual Reference Station (Base Station not required) ▫ Create DSMs and orthomosaics using reference station networks to achieve highly accurate absolute geotags. ▫ Useful when you want to benefit from the high absolute accuracy achievable using an Ntrip networks, or when surveying equipment is unavailable or inconvenient. Unknown point (Post process) ▫ Geotag relative to an approximate base station position, then post-process GNSS data to reach high absolute coordinate accuracy. ▫ Useful for green-field surveying when no GCPs have been set, when in-field time is limited, or it is impractical to survey beforehand. Known point (Use base station) ▫ Obtain high absolute coordinate accuracy using your precisely measured base station position as a GCP. ▫ Useful when a survey has already been completed and reference points are already marked out. No post-processing is needed to achieve RTK-level geotag accuracy. 9/22/15Ohio GIS Conference 10

A study of point cloud accuracy Two experiments were conducted 9/22/15Ohio GIS Conference 11 Flight OneFlight 2 Assess maximum accuracy of eBee RTK Assess impact of adverse lighting and weather on accuracy RTK using VRS Area: 49.4 acres GSD:.98 inch Imaging altitude: 266 ftImaging altitude: 531 ft Overlap: 80% Perpendicular flightsNo perpendicular flights Bright sunny dayCloudy (low light) and windy (20 mph)

Accuracy Measurements Accuracy was calculated using Root Mean Square Error 9/22/15Ohio GIS Conference 12 n is the number of points Xdata is the X coordinate of the dataset Xcheck is the X coordinate of a reference point

Results 9/22/15Ohio GIS Conference 13 Verification Points in the Point Cloud Orthomosaic and DSM Accuracy Conclusions: With high overlap and high resolution (2.5cm), we can see that, in these ideal lighting and weather condition, the 3Bee RTK can achieve a very high level of accuracy, both horizontally (2.6cm) and vertically (3.1cm) Conclusions: As both the DSM and orthomosaic are based on the point cloud, the final accuracy is clearly slightly lower, horizontally (3.3cm) and vertically (3.5cm)

Results continued 9/22/15Ohio GIS Conference 14 Inaccurate Geotags Low light, windy conditions Conclusions: Even with inaccurate geotags in 10% of the images, the accuracy of the entire dataset is maintained, thanks to the capabilities of Postflight Terra 3D Conclusions: Flights over the same zone during windy and low light level conditions demonstrated that the eBee RTK has no difficulty achieving one to three times GSD accuracy, in line with senseFly’s claims

Conclusions The eBee RTK offers a convenient and efficient method to to create accurate DSM without the need for ground control points Under ideal conditions, accuracy of 2.6 cm horizontally and 3.1 cm vertically was obtained Performance degrades gracefully under deteriorated environmental conditions, with demonstrated accuracy of 8.9 cm horizontally and 7 cm vertically. 9/22/15Ohio GIS Conference 15

References eBee RTK Accuracy Assessment A. Roze 1, J-C. Zufferey 2, A. Beyeler 3, A. McClellan 4 1 Application Engineer, senseFly, 2 CEO, senseFly, 3 CTO, senseFly, 4 Technical Writer, senseFly eBee RTK Extended Users Manual, Revision 1 / September 2014, senseFly Ltd. 9/22/15Ohio GIS Conference 16

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Virtual Reference System (VRS) VRS is a system of hardware and software designed to facilitate real-time GPS/GNSS positioning based on a set of reference stations Ohio Dept Of Transportation (ODOT) utilizes its CORS (Continuously Operating Reference Station) network (Trimble) to perform the role of the reference stations Eliminates the need for a separate base station 9/22/15Ohio GIS Conference 18

ODOT VRS RTK Network 9/22/15Ohio GIS Conference 19