Sun Hill Surveying & Engineering - Scanning by road and river

Author: Simon Hall

Introduction

Opened in 1862, Westminster Bridge has played a key role in the growth and development of London for over 150 years. Since the removal of Rennie's New London Bridge in 1967, it is the oldest road structure which crosses the Thames in central London. A structure of such historical significance requires a great deal of resources to maintain, including topographical surveys.

Sun Hill Surveying and Engineering Ltd is a specialist Land Surveying and Engineering company with over 30 years’ experience, focussing on the civil engineering sector throughout the UK. With over 7 years experience surveying with the Leica Pegasus:Two mobile mapping system, Sun Hill brings a modern approach to surveying with a unique combination of traditional and state-of-the-art technology.

Topographical survey, elevations and point cloud

In 2022, Sun Hill was tasked to undertake a complete survey of Westminster Bridge. This required the combination of both vehicle and boat mounted scans, with the aim of producing a topographical survey for the top of the bridge, extracted elevations for the bridge faces, and the delivery of combined point clouds for the entirety of the bridge.

Minimising disruption

As one of the major river crossings in London, Westminster Bridge has a constant flow of traffic and pedestrians crossing on a daily basis, along with extensive river traffic travelling underneath it. This presented a challenge to survey the bridge whilst causing minimal disruption to day-to-day activities of the area.

Permanent as built record of the bridge

To meet this challenge, Sun Hill utilised the multi-platform Leica Pegasus:Two mobile mapping system.

The Leica Pegasus:Two uses a laser scanner in combination with GNSS receivers, an IMU and 360 cameras, enabling Sun Hill to acquire complete, accurate and precise spatial data.

In the boat configuration Sun Hill maintained survey-grade accuracy by using an additional antenna to counter the pitch and roll of the boat and collected all required data in a single site visit.

Ground control on the bridge was used to accurately align the vehicle and boat mounted scans. Each bridge arch was scanned at multiple angles using the Pegasus system to provide a dense and complete combined point cloud.

Using this methodology, Sun Hill successfully captured 3D point clouds of the entirety of Westminster Bridge. From this, the requested datasets were extracted, and the point clouds themselves provided a permanent as built record of the bridge.

Increase efficiency and safety

The use of the Pegasus:Two mobile mapping system allowed the survey to be undertaken without the disruption of road and underbridge closures, a major factor in a successfully survey in this key location in Central London. This methodology ensured that the survey was completed quickly, accurately and reduced the risk to the surveyors and the public, compared to traditional surveying methods.

The Pegasus:Two is completely vehicle-independent making it an excellent solution across multiple applications, whether it be road, rail or river. Sun Hill successfully utilised this flexibility of the system to capture all the required data using a single solution.