Panmure & Auckland Harbour Bridges

Date: 2014-15

Background

Bridges and other structures spanning waterways present their own challenges when it comes to asset management and maintenance. The life spans of these structures are typically measured in decades with both the surface and subsurface components subject to a number of stresses and strains over long periods of time.

Requirements

The Panmure bridges in Auckland, New Zealand, provide a key arterial link into the city and are used by 1000's of people per day. The bridges span the Tamaki River which is subject to tidal flows 24 hours per day. Understanding the extent and nature of any scouring around the main bridge piles is key to managing these assets. To aid in this process DML provided a high resolution MBES survey of the areas immediately above and below the bridge piles.

The Auckland Harbour Bridge is an eight-lane motorway bridge over the Waitemata Harbour, joining St Marys Bay in Auckland with Northcote on the Northshore. The bridge is part of State Highway 1 and the Auckland Northern Motorway. It is a primary transport corridor and allows ships to access the deep water wharf at the Chelsea Sugar Refinery. The bridge was chosen to be the subject of a trial to test the simultaneous use of a vessel mounted, Terrestrial Laser Scanner (TLS) and MBES echo sounder.

Challenges

Two key challenges arise when utilising high end sensors designed to gather large volumes of point cloud data.

Challenge 1: Managing and understanding the six degrees of vessel motion using a survey quality Inertial Navigation System (INS) to correct TLS and MBES data increases the quality and accuracy of your final data sets.

Challenge 2: The careful online acquisition, management and processing of large volumes of point cloud data in real time is key to reducing post processing effort and deriving accurate results. Daily data volumes range from the hundreds of Gigabytes to Terabytes of data.

Solution

The solution requires highly experienced survey personnel using MBES systems for hydrographic surveys and/or the integration of both MBES, TLS and INS data within hydrographic survey acquisition software to produce 3D surveys of structures above and below the waterline.

Outcome

Clients receive highly accurate surveys of structures above and below the waterline. Deliverables include self contained 3D fly throughs, 2D & 3D images, bathymetric and topographic surfaces, volume calculations, survey plans and reports.
In the case of the TLS and MBES trial, DML showed that a TLS can be successfully integrated to an MBES acquisition system in order to simultaneously survey structures above and below the water line from a vessel.
DML will continue to expand its multi platform survey capability using TLS, MBES, SBES and digital aerial cameras on vessels, vehicles, remotely operated vehicles and drones for all modes of transport including water, road and rail.