Christ Church Cathedral, Christchurch, New Zealand

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Christ Church Cathedral, Christchurch, New Zealand

Christ Church Cathedral Reinstatement – creating a digital eye on the inside

On February 22nd, the Christ Church Cathedral, officially known as the Christ Church Anglican Cathedral, was one of many buildings damaged in the 2011 earthquakes that hit the heart of city. As reinstatement works of the historical building get underway, clearing the internal debris in a highly risky and unstable environment was always going to be a challenging problem to solve.

To avoid sending manned excavators into the cathedral, civil construction company Protranz partnered with Aurecon to adapt their innovative unmanned excavators to clear the debris from inside.

Losing the line of sight

The task of removing the debris presented such a significant health and safety risk that sending manned excavators into the damaged cathedral posed an avoidable threat to the lives of anyone entering the cathedral. Further complexity was added with heritage teams desperate to save as much as practicable, including pieces of the cathedral's famous rose stained-glass window.

The problem was the existing unmanned excavator needed an operator to have line of sight on the area where it is working. Once the machine disappears into the cathedral, the operator would be working blindly with no visibility of what was being picking up. Protranz wanted a solution that would allow them to have eyes on the inside to protect and track the location of any salvageable heritage items and to prevent the excavator from causing more damage.

Protranz and Aurecon have successfully partnered before on the remediation of Dean's Head following the significant cliff collapse that occurred after the 2011 earthquake. This previous partnership has meant Aurecon were already familiar with the unmanned excavators and this made it easier to build a digital solution for a dangerous and complex situation.

Giving operators eyes on the prize

Aurecon proposed a remote camera system of five individual cameras fitted at different points on the excavator to relay real-time video back to the operations centre outside. A sixth camera, located inside the cathedral, will give the operator a bird’s eye view of the location of the excavator. According to the excavator operator, the number one priority was for the live video feed to have zero latency.

After constant experimentation, Aurecon has been able to get the latency down to 1 millisecond or virtually undetectable. To put this into perspective, the average human reaction speed is 190 milliseconds.

Other important features include:

  • A camera on the front and back, left and right sides, and one located on the boom, giving the operator an almost 360-degree view of the inside of the cathedral. A sixth camera, located inside the cathedral, will provide a bird’s eye view.
  • All six cameras can record simultaneously, allowing teams to go back and review the work that had already been completed. The heritage team can also identify debris and which bin that debris went into to find salvageable items.
  • The camera system has Live Stream capabilities so team members who are not on site can check in and view the excavators progress, reducing the number of people needed on site.
  • The camera system can function up to one kilometre away, and again, reducing the number of people needed on site and their proximity to falling debris.
  • The camera on the boom has a zoom capability, allowing the operator to manoeuvre close to the columns and walls of the cathedral without causing further damage.
  • The entire system is designed to fit within a standard hard pelican case so it can be easily transported and set up on site.
By partnering with Aurecon, Protranz now has an innovative kitset system ready to use whenever a site becomes unsafe and visibility is impaired. Meanwhile, solving a significant Health and Safety and programme problem for Naylor Love and Christ Church Reinstatement Limited in the reinstatement of this significant structure.

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