Through making use of differing laser scanning technology and equipment, we can capture high accuracy laser scanning data and 3D models that give a full picture of the given area being surveyed. In this article, we will discuss recent examples of how the Merrett Survey Limited team made use of two different laser scanning devices, for underground assessments.
We’re constantly looking at how the latest technology can impact the speed, quality and consistency of our results. With this in mind, we recently utilised the Faro and Zeb-Revo laser scanners very effectively in two separate surveys. Whilst we work with aerial and ground based (terrestrial) lidar scanners, this article concentrates on the ground – or rather underground – based technology.
Merrett Survey Limited were recently asked to provide the orientation of underground mine workings to the surface. This was for a historic gold mine, which may be re-opened in the future. The purpose was to ensure that new exploration drilling from the surface would not hit old stopes and driveways, consequently resulting in expensive loss of drilling fluid and the need to install casing.
With only two outlets to surface through old adits, it was evident that the orientation of the ancient workings was going to prove difficult. However, we began by surveying a high accuracy traverse to obtain good control, with control ties at surface using GPS. The remote and high altitude location of the entrances made access very interesting too, where we required snowmobiles for the transportation of our equipment.
At this stage, we selected laser scanning to provide the highly detailed model of the workings, so that the 3D extent of all the accessible workings could be plotted accurately. This was achieved with a Faro laser scanner, which was selected for its compactness, ease of use and scan speed of up to 1 million points per second. Sufficient to see joint patterns and measure their dip and strike, which is a bonus for geologists, as well as recording the 3D orientation of the workings.
We recently trialled a different piece of laser scanning technology altogether, while mapping Exeter’s underground passages. Our mining team tested the use of a SLAM (Simultaneous Localisation and Mapping) based scanning system, and in particular the Zeb-Revo, on a test bed circuit in the historic Exeter passages. These tunnels were built in medieval times to enable a fresh water supply to be brought into the heart of Exeter City. They are open as a tourist attraction although we surveyed many of the routes not open to the public.
Throughout the course of testing this scanning system we proved that, with the right methods, we can scan hundreds of metres per day including down to sub-metre width passages. This is something the manufacturer, Geo Slam, claimed was not possible. We were delighted to have exemplified this feat and to discover the full potential of this laser scanning system.
Although the SLAM method is ideal for scanning narrow spaces and its phenomenal speed facilitates rapid assessments of passage/stope size and orientations, it does not provide the high scan density and high accuracy of the Faro method.
The testing of the latest, most technologically advanced laser scanning equipment results in our team knowing how to achieve the most intricate and thorough mining surveys.
These are just two recent examples of how we’ve used our industry experience and up to date knowledge of the most groundbreaking 3D laser scanners, to efficiently survey underground workings. Contact us to learn more about our underground laser scanning and mining survey methods, and discover how we can be of assistance in your current or next project.