C+S February 2020 Vol. 6 Issue 2 (web)

Houston’s job was to collect information on topography and soils for use in planning and design of the temporary facilities. “In addition to the workplaces, we needed to find sites for pens and medical facilities to keep the buntings and moorhens contained so they don’t eat the poi- soned bait,” he said. Houston explained that the island-wide mitigation would be conducted during the southern winter while the other sea- birds’ migration and feeding patterns took them away from the island. Precise Mapping in Remote Locations In order to conduct the design work, Taylor & Boyd needed accurate information on the terrain and existing structures. Adding a surveyor to the team was cost prohibitive, so Houston performed double duty by handling tasks in both surveying and engineering. With only two weeks to complete his work, RTK GNSS seemed to be an ideal solu- tion for the treeless locale. But Houston’s lack of survey experience and the absence of geodetic control or cellular service on the island combined to make RTK unfeasible. Instead, he used a Trimble® R10 GNSS receiver in conjunction with Trimble CenterPoint® RTX cor- rection service. CenterPoint RTX uses a global network of GNSS reference stations combined with satellite communications to enable users to achieve real-time, centimeter-level positioning accuracy, even in the most remote locations in the world. Using a Trimble TSC3 controller and Trimble Access™ field software with the R10, Houston collected hundreds of 3D points around the project site. He captured the location of existing structures and features, test pits for soil evaluation, and ground points for use in topographic modeling. Using the display on the TSC3 he could follow his progress and make sure he covered the necessary ground. In spite of working more than a thousand kilometers from the nearest GNSS reference station, Houston achieved centimeter accuracy on all survey points; typically 3 to 5cm in both the horizontal and vertical components. A typical workday lasted 10 hours or more. “The weather and terrain made life miserable,” Houston recalled. “It’s cold and windy and we needed to wear waterproof clothing. The area is overgrown with brush

from Gough Island. The work involves distributing poisoned bait that will attract and kill the voracious rodents. It’s not the first time that an entire island has undergone mouse eradication. Similar projects on South Georgia Island and Antipodes Island have successfully removed populations of introduced rodents and restored a more natural balance to bird populations in those sub-Antarctic locations. And in the warmer waters north of Hawaii, Midway Island has also received the anti- rodent treatment. With the Gough Island eradication project planned to take place in 2020, RSPB began planning for facilities needed to support the work. They received permission to establish temporary infrastructure to house, feed, and support the taskforce. Because most of the bait will be spread using helicopters, planning also included landing pads and fuel and maintenance installations. The overall goal is to guide installation of the temporary structures with minimal impact on Gough Island’s native flora and fauna. The TSC3 displayed all the points captured with GNSS. The data were later transferred to CAD software for mapping and design.

Amendment Rev

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ConsultingStructuralandCivilEngineers www.taylor-boyd.co.uk

Belfast: (028) 9066 7951

Derry: (028) 7126 7115

Project:

DwgName: RSPBPROJECT GOUGH ISLAND 3DVIEWOF TOPOGRAPHICALSURVEY

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RSPB

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Not toScale FEB2019

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A 3D model of the work area on Gough Island. Points were captured with accuracy of 3 to 5 cm.

Taylor & Boyd developed a 2D drawing of existing facilities. They also produced proposed locations for temporary structures for the mouse eradication project.

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