Complex integrated survey of Bristol Harbour

In one of our most significant and complex projects to date, Glanville Geospatial Services has undertaken a full survey of Bristol Harbour, above and below the waterline.  Our work has contributed to a quay wall condition survey, commissioned by Bristol City Council.

• Multi-Beam Echo Soundings (MBES) of the quay wall below the waterline, providing a 5cm resolution dataset
• colour LiDAR surveys of the harbour wall above the waterline, and surrounding area, providing a 5mm resolution colour dataset
• georeferenced still photography every 2m covering over 15km of quay wall
• 2m grid of depth soundings across the entire harbour bed

Bristol Harbour is a long, thin, winding body of water, with several inlets and bridges, surrounded by a dense urban environment.  It extends for five kilometres from the River Avon at Cumberland Basin in the west and runs through the heart of the city, connecting back into the River Avon at Netham Lock in the east.  To make this complex task more manageable, the harbour was divided by Bristol City Council into six zones.  Within each zone short sections of wall were assigned an ID or sub set reference – this would enable the planning, execution and delivery to be split into bite-sized chunks.

An initial survey was conducted in the summer to provide a baseline dataset that would assist with planning the more challenging detailed survey in winter. A Leica Pegasus mobile mapping system was deployed on a boat in the summer months for the baseline LiDAR dataset collection.

Following this, and working closely with the Harbour Master’s office, each subset of quay wall had moored boats removed in sequence, with the survey teams following in behind to complete terrestrial laser scanning, MBES and photography during the detailed survey in winter.

Georeferenced still photography was shot from a RIB using a DSLR camera, retro fitted with high precision GPS, enabling centimetre grade geotagging.

Multibeam Echo Sounding of quay wall and toe was acquired using a small unmanned vessel (USV) that with its size and manoeuvrability increased data coverage by 15-20% over a traditional manned survey vessel, accessing areas behind pontoons and shallow zones a bigger vessel could not have entered. In addition data coverage and quality was maximised through the custom fabrication of a tilted MBES head, designed to optimise data collection on wall face and toe/bed simultaneously.

The final dataset was huge. The management and transfer of data between stakeholders was only one of the challenges on this project – the logistical challenge of moving all boats out of a major harbour whilst synchronizing multiple survey teams made the fading winter light and challenging weather seem easy!

Many months of planning and execution has created what must be one of the largest and most comprehensive survey datasets in the country.