Laser-based scanners, GPS and sophisticated software are all available to today's mine survey office, supplementing more traditional instruments. E&MJ reports on some of the more popular systems on the market.
"An inaccurate survey is valueless, in fact a poor survey is often worse than none." Words that were written by American engineer, educator and businessman
"One of the essential things for a mine surveyor to appreciate is the accuracy demanded of him." Young went on, before adding somewhat pointedly, "Much litigation may be avoided if the mine is properly surveyed."
Today, the mine survey office is equipped with instrumentation and software that would be far beyond the imagination of Young and his contemporaries. The often beautifully crafted one-off mine plans of the 19th and early 20th centuries have been replaced by on-screen and laser-printed documents, mass-produced on demand. And, of course, a beautiful hand-drawing was no guarantee for enhanced accuracy: mine plans were only as good as the original surveying would permit, and could easily be misleading if the surveyor had made mistakes.
Even now, Young's comment about litigation can resonate, albeit usually from the perspective of health and safety issues rather than the claim-jumping to which he alluded later in the book. For example, a recent corporate manslaughter trial in the
Current-generation surveying systems provide the mine surveyor with the means both to produce highly accurate plans, and to manipulate survey data to give 3-D representations of operations and projects. In addition, setting out underground has been simplified through the use of tunnel lasers, while laser-based leveling systems have added a new level of precision to surface excavation.
Over the past 18 months, E&MJ has looked at a range of surveyingand mapping-related topics, including digital mine mapping (
Lidar Sensors from Leica
In June, Leica Geosystems was one of the participants at the HxGN Live corporate conference in
Tools available for underground surveying include Leica's boom-mounted robotic cavity monitoring system, which can provide survey data from environments such as open stopes. Operated by remote control from a safe location, data are gathered and transmitted wirelessly.
For processing data, Leica's fieldPro provides an interface to combine AutoCAD software with Leica total stations, enabling the surveyor to work directly on 3-D mine designs while superimposing measurement data. The system includes mining-specific layout and markup functions for underground surveying, and allows features such as overand under-break to be displayed.
Leica's airborne sensors can be tied in with products from another Hexagon company,
The company cited the example of a
Locata: Local Positioning Networks
Not only does this provide extremely accurate and reliable GPS-like services but it simultaneously resolves many satellite-based PNT shortcomings, Gambale added, including the ability to reach areas where GPS is degraded or denied.
Open-pit mining has been an eager early adopter of Locata, he said. With drill rigs needing better than 100-mm (4 in.) accuracy to achieve effective controlled drilling automation, mines have attempted to use GPS receivers using standard survey-grade techniques. However, this approach becomes less effective as the pit depth increases, since satellite-only receivers cannot calculate an accurate position when too few satellites are available.
To solve this problem, Leica Geosystems has developed the world's first GPS+Locata receivers for use in open-pit mines, tracking both GPS and Locata signals simultaneously. This provides centimeter-level machine positioning, even when RTK (real-time kinematic)-GPS fails completely, Gambaie stated.
Locata reported that Newmont's Boddington gold mine in
Total Stations from
While much of the focus is understandably on the larger scale of things, there remains a real need for "traditional" types of survey equipment that can be used for site-specific and underground surveying. Most of the world's manufacturers of survey equipment include this type of instrument in their product portfolios, albeit considerably more sophisticated technologically than the theodolites and levels that Young was familiar with in the early 1900s.
As an example,
Perhaps designed with mining and exploration in mind, the instrument's IP65 waterproof cover helps exclude dust and driving rain, while the instrument itself can be used in temperatures from -20°C to 50°C.
Security is also built into the DS series,
Riegl: Laser Scanners
The Austrian surveying equipment manufacturer, Riegl, used the last MINExpo in
The instrument joined the VZ-4000 model, which equipped with an eye-safe laser, can make up to 222,000 measurements per second at a maximum range of 4,000 m. Both models are designed to work with Riegl's RiMonitor and RiMining software packages, with RiMonitor used for monitoring pit walls for signs of potential instability.
RiMining is a software package for optimized and simplified scan data registration and processing in open-pit mining. Riegl said the main applications include surveying in open pits, quarries and dump sites, monitoring excavated and filled areas, and making mass calculations, as well as extracting input data for site modeling. RiMining speeds up field-surveying, the company added, providing workflow automation and automatic data registration. VZ-Line laser scanner field-data can be imported and registered without any targets, so reducing the survey times on site.
Mobile Mapping with Zebedee
3D Laser Mapping recently acquired the rights to commercialize a mobile Lidar scanner developed by the Australian research organization, CSIRO. Now marketed as the ZEB1, and nicknamed Zebedee after the character in the French-British childrens' TV program The Magic Roundabout, the handheld instrument offers a number of benefits when it comes to surveying stockpiles, buildings or excavations, the company said.
These include its ability to scan large areas quickly, at walking speed, to gather 3-D point clouds in areas with no GPS coverage, its low training needs, automated data processing and the fact that the unit is lightweight, at just 700 g.
The ZEB1 uses robotic technology called Simultaneous Localization and Mapping (SLAM). The system includes a lightweight laser scanner mounted on a simple spring mechanism, which continuously scans as the operator walks through the environment. As the scanner loosely oscillates about the spring, it produces a rotation that converts 2-D laser measurements into 3-D fields of view.
The company cited an example of using the ZEB1 to survey a covered stockpile at a mine in
Hands-off Void Measurement
Surveying voids, such as open stopes, abandoned mine workings or orepasses, is probably the most hazardous task in the mine surveyor's handbook. Now integrated into the
In-built sensors ensure the C-ALS can be tracked down a borehole and that the scan is automatically geo-referenced to fit into existing 3-D mine data. Once in the void, a simple click from the operator tells the laser-scanning head to rotate on two axes, measuring the 3-D shape of the void, with full 360° coverage and a range of up to 150 m.
An example provided by
Speeding Shaft Surveys
The MS3 automated shaft inspection and monitoring system, developed by the Canadian company,
"As it stands," he said, "the MS3 is not available as an off-the-shelf system, but consists of custom hardware and software set up and tailored to a client's needs and environment. Because of this, we have partnered with the German company DMT to provide a cheaper and a more universal solution for ad-hoc shaft inspection and/or monitoring," he added.
The systems involve the use of a Lidar-based laser scanning system, together with other sensors, that are mounted on either a cage in an working shaft, or are cable-suspended where old or rarely used shafts need to be surveyed. A 1,500-m-deep shaft typically takes less than a shift to survey, with the cloud point data collected then processed in Shaft Inspector software to produce accurate 3-D images of the shaft and all of its infrastructure. Where repeated surveys are undertaken over a period of time, changes in the condition of the shaft structure or service ranges can be identified accurately.
An Aerial Imaging Solution
Trimble describes its UX5 Aerial Imaging Solution as a complete unmanned aerial imaging system specifically designed for surveyors and geospatial professionals. A fixed-wing aerial vehicle weighing 2.5 kg, and with a 1-m wingspan, the UX5 is not a remote-controlled UAV, but is pre-programmed, using waypoints during flight.
Used to perform boundary and topographic surveys, site planning and inspections, progress monitoring, volume calculations and post-event analysis, the UX5 has a 60-km range and 5,000-m ceiling. Operators use Trimble's Access Aerial Imaging application running on a tablet PC for flight planning, pre-flight checks and flight monitoring. In the field, the operator is guided through the preand post-flight sequences with step-by-step digital checklists.
The company stated that the UX5 delivers optimal image quality along with maximum photogrammetric accuracy. It has a large imaging sensor that captures very sharp, color-rich images, with a camera and custom optics to capture data down to 24 mm resolution. From a single flight, operators are able to generate feature maps, topographic contours, 3-D surface models and orthophotographs, while the data obtained can be processed into outputs such as digital surface models (DSMs), digital terrain models (DTMs) and true orthomosaics.
Trimble told E&MJ that it is also focused on extending the value and use of its surveying technology in mining applications. For instance, the
The angular accuracy of the total station combined with a network of GNSS sensors and prisms is suitable for the detection of both toppling and slumping failures on a highwall, Trimble added.
A World Beyond UAVs
According to the Australian company, Sandpit Innovation, the mining sector currently uses a combination of ground surveys and aerial fly-overs, with the use of drones starting to emerge, to determine stockpile volumes on a monthly or more frequent basis. Sandpit has now partnered with
While the application of satellite imagery is new to mining, the technology is well-proven, low-risk and continues to evolve rapidly. Currently, nine commercial satellites send back high-resolution imagery to the earth. By the end of 2015, that number is projected to exceed 40 and by 2017, more than 75. Sandpit provides full custom reconciliation reports, including volume reports based on operational requirements, change detection mapping and filtration, and 3-D modeling, as well as the digital elevation modeling (DEM) data.
Satellite imagery is collected in under 10 minutes, without any interaction on site. It is non-intrusive and eliminates all HSE risks, the company noted. Advanced processing techniques then allow accurate and repeatable elevation data to be extracted, along with change detection and image filtration, to produce high-quality volume calculations. Other advantages include the system's ability to capture several mine sites in a single image, and lower costs than current aerial surveying methods, Sandpit stated.
* While long out of print, A Study of Mine Surveying Methods and Their Applications to Mining Engineering can be downloaded from www.forgottenbooks.org.
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