Delivering Better Surveying Outcomes on the Rail Network Growth Impact Management (RNGIM) Project

Sam Hackett staff photo
Associate Surveyor Mobile Mapping

Surveying 40 kilometres of the rail corridor is quite an onerous task. Read on to see how Woods’ surveying team created cost and time savings while improving health and safety on the KiwiRail RNGIM project.

At Woods, we are always optimizing and refining our field and office processes and our methodologies to enhance the accuracy and the quality of the products we deliver. So when KiwiRail needed 40 kilometres of rail corridor surveyed over three different Auckland Metro rail lines, we jumped at the challenge to design a solution that could deliver above and beyond what most standard solutions and conventional technology could provide.


The Rail Network Growth Impact Management (RNGIM) is a KiwiRail project that consists of a collection of fairly major supporting works across the Auckland rail network. This project is designed to help build more resilience into the rail network and mitigate the impacts of the increased train number of trains running through the network once the City Rail Link (CRL) opens in late 2024.

As part of the RNGIM project, KiwiRail needed a survey of about 40 kilometres of the rail corridor spanning three different rail lines. They also needed this survey to be done fairly promptly in order for the design works and planning to get underway.

The challenge of rail corridor access limitations

Surveying 40 kilometres of the rail corridor is quite an onerous task with the main challenges being access and health and safety. With all the areas to be surveyed located within the Auckland metro network, no real work within the rail corridor could be carried out during the day as trains are running every 20-30 minutes (or 15 minutes at peak times). The only time work can safely be completed is at night outside of the metro train timetables.

We estimated that completing the survey with a conventional method would amount to about 1500 worker hours in the rail corridor and roughly three months to carry out the fieldwork because of the limited access. The only way to make this solution cost-effective would have been to postpone the fieldwork to the Christmas shutdown period, and use a very large crew to complete the task over the three weeks trains are shut down for Christmas.

We weren’t too happy with that being the outcome, so we set about designing a new methodology to create a better outcome for the client.

Designing and delivering a new methodology

By combining many of our surveying technologies (mobile laser scanning, terrestrial laser scanning, and GPS surveying), we were able to reduce the worker hours required in the rail corridor by about 90%. This was not only a cost-saving for KiwiRail but also a massive health and safety improvement for our team.

Using mobile laser scanning as the key tool for data collection, we were able to survey the rail corridor while driving along the rail track after the last metro trains had run, between midnight and 4am.

This meant that instead of 1500 worker hours in the rail corridor, we only needed five shifts with the rail vehicle to capture the laser data.  These work hours plus other related survey tasks accumulated roughly 120 worker hours in the corridor.

Creating a solution that sets us apart and delivers higher value

The outcome of this project epitomizes our mission and our drive at Woods to not only optimise the solutions we deliver but also optimise how we can do it safely. Using our in-house state of the art technology and extensive knowledge of surveying principles and methodologies, we were able to carry out the work in a way that would otherwise not have been available to our client and with reduced health and safety risk.

The new methodology achieves all the standard outcomes that a conventional survey methodology would, but with additional value. Because we used mobile laser scanning, we were capturing very feature-rich raw data that KiwiRail can load into their digital engineering platforms to create a digital twin - a highly accurate 3D detailed picture of the rail corridor with laser point clouds and 3D models.

This enables KiwiRail to apply very modern workflows within their data management. Major contractors can log in to KiwiRail’s digital data platforms and interact with comprehensive data, leading to increased efficiencies and accuracy. Often, if we view a presentation from KiwiRail, we can actually recognize the data because it came from us. It’s something we are always very proud of.

Staying at the forefront of surveying

While we have carried out surveying projects like this previously, we are always learning new little tricks of how we can enhance, optimize, and make our workflows more efficient, or ways that we can redesign processes in the field to be safer. This gives us the capability to design and deliver surveying and spatial solutions that are quite set apart from what most other technologies can provide.

Sam Hackett - Associate Surveyor, Mobile Mapping

Contact us to find out how we can help with your project or visit the Surveying & Spatial page of our website for more information on Woods’ surveying capabilities and offerings.