C-ALS® borehole deployable laser scanner for concealed cavity and void scanning

C-ALS® is a totally unique, specialist underground laser scanner.

With C-ALS, you can map the most inaccessible parts of mines, safely and quickly, with an accuracy never possible before.

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The C-ALS can be used in a huge range of applications, wherever an inaccessible void exists and accurate data is required to monitor excavations, assess risk or design solutions.

Once deployed, the C-ALS gives more detailed, accurate data than alternative technologies, such as ground penetrating-radar, and is the only borehole-deployable laser solution on the market.

  • Plan new projects: assess risk, design solutions based on accurate underground data, add C-ALS data to your existing maps and devise new programmes of work.
  • Improve productivity: with accurate maps of voids, you can design plans, which allow for efficient mining or construction projects.
  • Improve safety: map inaccessible underground areas to ensure operations keep employees safe.

How the C-ALS supports successful projects

Ruggedised PC for C-ALS

C-ALS gives you new underground mapping capabilities. You can safely, quickly and reliably scan inaccessible underground workings, and upload the scan data to your existing mapping software, giving you the information you need to:

  • Protect worker safety
  • Show compliance
  • Report to project stakeholders, in greater detail
  • Cost out planned works accurately
  • Devise more efficient programmes of work
  • Progress new projects
  • Design and engineer solutions based on accurate data
  • Minimise disruption, drilling and disturbance in populated areas

Advantages of laser scanning with C-ALS

3D cavity scan

The C-ALS system's unique 50 mm diameter allows deployment into cost-narrow boreholes, and the 360° spherical coverage gives you a full view from a single scan, without blind spots.

In addition, C-ALS offers the following benefits:

  • Survey potentially dangerous underground voids in complete safety
  • View results in minutes, not days
  • Remotely controlled operation
  • Flexible deployment methods
  • Easily transported
  • The IP67 rating gives you the confidence that the system will operate in wet, humid and dusty conditions. It can also withstand submersion to a depth of 1m, reducing the risk of damage if C-ALS is accidentally deployed into flooded cavities.

How it works

C-ALS and borehole

With a diameter of just 50 mm, C-ALS is easily deployed through boreholes, downhole or uphole to survey inaccessible spaces.

A system of hinged, lightweight one-metre rods provide a fixed azimuth capability, as well as giving you the ability to deploy the C-ALS down boreholes as long as 200m. The C-ALS can also be deployed by boom or by remote-controlled vehicle.

A nosecone camera gives you full visibility of the borehole during deployment, so operators can see any obstructions, as well as judge the point when the C-ALS enters the void.

The C-ALS® probe incorporates pitch and roll sensors and has the option of an internal compass. The sensors ensure the C-ALS can be tracked down the borehole and that the scan is automatically geo-referenced to fit into existing 3D mine data.

Once in the void, a simple click from the operator tells the laser-scanning head to rotate on two axes, measuring the three dimensional shape of the void, with full 360 degree coverage and no blind spots, and with a range up to 150m.

A load-bearing cable attached to the probe transmits all the measured data back to the surface unit and a ruggedised computer is used to control the C-ALS® from a safe location and to view the data in real-time.

New, user-friendly software

C-ALS splash screen

Renishaw's new software for C-ALS makes it easier and quicker for operators to use the system, by guiding them through the process of deploying and scanning.

  • Quicker navigation and intuitive design supports new operators and speeds up training
  • Software, viewable on the connected, ruggedised PC included in the C-ALS package, shows the scanner's inclination and heading at all times
  • One-click surfacing and volume calculation from raw scan data enables you to obtain a closed 3D model and volume within seconds of finishing a scan
  • Point cloud editing and visualisation can be conducted on site to support swift operations
  • Auto-connection to the C-ALS probe reduces setup time
  • Live recording from the C-ALS camera into WMV makes it easy to save and share video footage
  • Export to a number of industry-standard formats, including LAS and DXF, allows easy integration with third-party processing software packages

Applications where C-ALS provides data when man-entry may not possible:

  • Sub surface voids and cavities
  • Undercrofts
  • Underground chambers and tanks
  • Duct surveys
  • Inaccessible roof spaces
  • Subsidence investigations
  • Collapsed mine workings
  • Culverts
  • Shafts and bunkers
  • Underground caverns
  • Industrial production facilities where access is limited or unsafe

Cavity surveys to support underground or surface mining projects

Underground mine with tracks and lighting

The existence of an underground mine void does not necessarily represent a significant subsidence hazard. By using C-ALS to determine the size and extent of the openings, spacing and size of pillars, mining customers have been able to evaluate and accurately assess risks, and in many cases prepare for ambitious new mining programmes, by ensuring project plans are safe.

Mine managers will want to have a complete picture of the situation underground before committing to projects or deploying workers, and the C-ALS supports them by providing key data on:

  • Excavation and infill of stopes
  • Accurate location of void 
  • Geometry and condition of mine workings (intact, collapsed)
  • Inaccessible historic workings
  • Collapsed areas
  • Erosion of ore-passes
  • Volumes of voids
  • The position of cavities in relation to other underground workings and structures
  • Size of remaining pillars
  • Failure mechanisms (sinkholes, troughing)
  • Location of the workings relative to surface features

The C-ALS is ideal for providing 3D data on inaccessible underground cavities. Mine managers can assess the stability of mine works and judge whether or not an underground cavity needs to be filled, whether work can proceed, and what project plans should be put in place to ensure that productivity and safety are maximized.

Open pit operations taking place over historic underground workings can pose serious threats to worker safety. The old mines will frequently be poorly mapped or will have shifted over the years due to collapse, void migration, flooding and seismic activity. A full understanding of the layout of the underground workings and their relation to surface operations is essential to be able to carry out safe open pit operations with heavy machinery, explosives and personnel.

Traditionally, it has been very difficult or dangerous to collect this information. The C-ALS can be used from the surface to map out the network of old voids and to provide detailed visual record of the subsurface environment. 

Void surveys in construction and geo-technical projects

C-ALS deployment on zipwire

Many different construction and geotechnical projects may need to identify, measure and map voids below the project site. Where such voids cannot be easily or safely accessed, various technologies such as ground penetrating radar may be used to detect the void, but results can be limited by depth and geology and can be difficult to interpret.

C-ALS is ideal for such applications. After locating the approximate position and extent of the void/cavity from GPR or previously held data, a borehole is drilled in to the void or cavity and the C-ALS is deployed via the borehole or other small access point. Once in the void the laser head opens out to measure the 3D shape of the complete void. The scan data can then be analysed visually, measurements can be taken and a volume calculated.

Pre- and post-construction subsidence surveys

Subsidence illustration

The presence of old mine workings or voids underlying residential and commercial properties, transportation and infrastructure facilities can cause differential settlement, sinkholes or even catastrophic collapse.

Whilst historic mine maps can help determine the geometry of voids, their depth and the nature of overlying strata, they do not help identify the results of retreat mining, pillar theft, spontaneous collapse or other subterranean movements.

Engineering solutions can be put into place to counter problems caused by old underground workings, but designing these solutions requires a complete picture of the situation underground. By deploying the C-ALS into these otherwise inaccessible areas, the required data can be collected and the area comprehensively mapped.


  • Brochure: C-ALS® Cavity Auto-scanning Laser System Brochure: C-ALS® Cavity Auto-scanning Laser System

    C-ALS is a unique laser system that gives you new underground mapping capabilities. You can safely, quickly and reliably scan inaccessible underground workings, and upload the scan data to your existing mapping software.

  • Data sheet: C-ALS® Cavity Auto-scanning Laser System Data sheet: C-ALS® Cavity Auto-scanning Laser System

    Detailed list of technical specifications and dimensions for Renishaw’s C-ALS Cavity Auto-scanning Laser System, the borehole-deployable laser scanner for concealed cavity and void scanning. With its unique 50mm diameter, C-ALS can enter otherwise inaccessible areas through very narrow, more cost-effective boreholes, enabling you to map subterranean cavities and plan safer, more effective operations.

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Next steps

Contact us online if you require more information or you have a pricing query, or alternatively you may like to speak directly to your local Renishaw office.