SSEN Case Study

Access Tracks Topographical Surveys using UAV

PROJECT NAME: SSEN Access Track Surveys

AREA: Scotland

SERVICES: Topographical Survey using UAV and ground techniques of 21 sub-station access tracks

CLIENT: Scottish and Southern Electricity Networks

Background Information:

June 2020 GeoAccess was awarded a framework contract, along with 2 other suppliers, with SSEN for 4 years providing UAV services across their portfolio.

In January 2021 we were successful on a mini tender as part of this framework for the topographical survey of 21 sub-station access tracks across the Scottish region.

The remit was to undertake baseline surveys of the access tracks using UAVs, picking up; track position, dimensions, condition, any structures, bridges, culverts, water courses etc; Condition assessments in line with Highways standard CS454, with outputs as tagged shape files, DXF, DWG, LAS and LAZ, as well as a rendered 3D mesh and 2D orthomosaic.

As previous base knowledge of the access tracks was lacking, we undertook a desk study and land registry search for land ownership and contact details. Access tracks ranged in length from a few hundred meters to 16.8Km.

Site checks and RAMS completed our operatives established a safe system of work on each site, sometimes liaising and working with other onsite contractors.

GeoAccess Services:

We decided to undertake the flights with our DJI M210 rtk UAV and X4S payload. A suitable flight height was chosen to match our required Ground Sampling Distance, with flight areas established suitable for battery duration and terrain. Ground Control was setup in the form of Propeller Aeropoints.

Propeller Aeropoints were chosen for the ground control over more traditional methods due to the quick deployment, accuracy levels and improvement in overall workflow that they provided. GCPs typically had a global accuracy of +-20mm in the XYZ.

Before leaving site, the operatives undertook Quality Assurance on the data and any issues were rectified before moving to the next area or leaving site.

To complement the aerial work, our highly experienced site crews (also geotechnical and structural engineers) undertook a ground survey of the points of interest. A baseline condition assessment was conducted on bridges, earthworks, culverts, watercourses etc and a report produced to compliment the data set.

Results:

UAV and GCP images were processed using Pix4D Mapper with some of the GCPs used as check points for accuracy. Processed in Pix4D Mapper the orthomosaic, point cloud, 3D mesh, DTM, DSM and contour plan were produced. Accuracy reports were checked for errors in processing and if required the data was re-processed. Data accuracy was also checked against known checkpoints within the model.

Following Pix4D Mapper processing the data was further processed in Pix4D Surveyor to produce the GIS Shape Files of all of the features on site. Pix4D Surveyor is an excellent halfway house between GIS and CAD software platforms. The software uses the point cloud data along with the georeferenced, orthorectified photographs to enable the operative to efficiently markup points, lines, and polygons of interest with 3D spatial coordinates. These layers are then saved as shape files and dxf / dwg ready for upload into GIS packages.

Working in Scotland undertaking UAV Photogrammetry work in the winter required some careful planning, but with good communication with the client and landowners we were able to undertake the project in a timely manner.

GEOACCESS LTD

The Old Dairy
Pessall Lane
Tamworth
Staffordshire
B79 9JL

T: 0333 772 2315

E: info@geoaccess.co.uk

SERVICES

Asset Inspections
Access Solutions
Ground Investigation
Enabling Works