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How to pick the right tags for tracking in underground mining

Miners have a wide variety of tag and tracking technologies to choose from, each with its own requirements and benefits. In this article, we cover the types of tags used in underground mining, their related radio network requirements, some pros and cons of each technology, and new developments on the horizon.

Tags help keep track of people, vehicles and important assets within a mine. In a relatively brief time, tagging technology has evolved from simple processors to smartphone apps that act as a “virtual tag”.  As the need for real-time situational awareness grows in underground mining, tags play a critical role in supporting everything from shift planning to safety protocols to autonomous vehicle navigation.

 

Tracking with tags can be performed both actively and indirectly. People and mobile assets, including light vehicles and heavy mining machines, often need to be tracked in real-time for safety and productivity reasons. Active tracking tags provide that crucial real-time awareness. Active tracking usually involves a Real-time Location System (RTLS) tag that utilizes various localization technologies to register and report the location of tags in a near real-time fashion. The more advanced tags are, the more energy they require. Hence, active are usually rechargeable.

 

In addition to mobile assets, there are typically large quantities of fixed assets in a mine, which usually stay in the same location for an extended period of time. Fixed assets include things like pumps and control units, boxes of vital spare parts, electrical outlets, network switches, fire extinguishers, and heart starters.

 

To lower cost, instead of using an active tag for these objects, an indirect tracking method using battery-powered Bluetooth® Low Energy (BLE) beacons can be used. With a battery life of three to four years, BLE beacons are indirectly located by other active tags that pass by and register the last known location.

Overview: Tag technologies for underground mining

Choosing the right tagging technologies for underground mining can be made based on the criteria of accuracy, effectiveness, network requirements and, of course, cost. There’s also a bit of psychology and change management strategy involved. 

Tag technologies covered:

  1. Radio Frequency Identification (RFID) Tags
  2. Wi-Fi Tags
  3. Ultra-Wideband (UWB) Tags  
  4. Virtual tag mobile apps
  5. Bluetooth® Low Energy (BLE) beacons

1. Radio Frequency Identification (RFID) Tags

RFID tags are small radio transponders that transmit data to a radio receiver, which is connected to a transmitter antenna. Passive tags are powered by radio waves emitted by a reader, while battery-powered active tags offer extended range and functionality. When triggered by an electromagnetic pulse from a nearby RFID reader device, the tag transmits digital data, usually a unique identifying number. The tag can't receive data, so communication with the reader is one way. 

Radio network requirements for RFID tags

RFID tags can be used for effective localization and tracking within a Wi-Fi or cellular network. RFID systems require a network of readers and antennas placed throughout the mine site. The range and coverage depend on the type of RFID tags (passive or active) and the frequency used. 

Accuracy, effectiveness and cost of RFID tags

In mining, RFID tags can be embedded in worker IDs, equipment such as helmets, or even integrated into the mining infrastructure. RFID tags are widely adopted and can be very cost-effective, but they provide limited data and accuracy when it comes to positioning and tracking.

 

The old paradigm was that readers would be placed strategically throughout the mine. A 100 kilometer mine might have ten readers, dividing the mine into 10 kilometer zones.  When a person with a tag passed the reader, it didn't say where that person was currently located, it just said that they passed this reader at a certain time. So, you could assume the person carrying that tag is in that zone, but that could be an extremely large area. 

 

Today, algorithms can be applied to more accurately position an RFID tag within the network coverage area, which can be visualized in the control center based on actual measurements.

Pros of RFID tags:
  • Reliable tracking and access control
  • Passive tags are cost-effective
  • Widely adopted in the mining industry

Cons of RFID tags: 

  • Limited range and susceptible to interference 
  • One-way communication provides limited insight
  • Requires a dense network of readers for effective coverage

2. Wi-Fi tags

Wi-Fi-based tags leverage existing Wi-Fi networks to determine their location using positioning algorithms. Using Wi-Fi tags, mines can enable effective localization of personnel and mobile assets within their Wi-Fi network coverage area. Wi-Fi tags can be integrated with sensors to monitor environmental parameters underground, including gas concentrations, temperature, and air quality. When combined with real-time location tracking, environmental awareness supports a unified approach to safety and risk mitigation. 

Radio network requirements for Wi-Fi tags

Depending on accuracy needs, using Wi-fi tags for tracking and positioning can require a relatively high volume of Wi-Fi access points, typically many more than are used to handle Wi-Fi data loads in mines. Lack of standardization across different Wi-Fi solution vendors can limit compatibility between systems.

Accuracy, effectiveness and cost of Wi-Fi tags

Wi-Fi-based tags offer reliable communication and can cover large areas, when supported by the appropriate network infrastructure. Wi-Fi accuracy is limited by sample rate and distance, while BLE beacons offer more accurate location tracking. Bluetooth and Wi-Fi can be used together to create a hybrid for positioning, but it's costly and requires many anchor points. Additionally, Wi-Fi tags consume more power than BLE beacons, leading to a relatively shorter battery life.

Pros of Wi-Fi tags:

  • Utilizes existing Wi-Fi infrastructure
  • High data transfer rates and accuracy in line-of-sight conditions
  • Ability to integrate with other systems 

Cons of Wi-Fi tags:

  • Requires a robust Wi-Fi network
  • High power consumption leads to shorter battery life
  • Lack of standardization across Wi-Fi solution vendors  

3. Ultra-Wideband (UWB) Tags

UWB tags utilize high-frequency radio technology for low-latency data transfer. UWB tags transmit a unique identifier in 1-2 nanosecond pulses across a wide bandwidth of frequencies, typically within the spectrum of 3.1 GHz to 10.6 GHz. Still an emerging technology, UWB is used today mostly to support advanced navigation and collision avoidance technology, rather than for real-time tracking and positioning. Through triangulation, UWB tags can provide the data needed for near real-time 3D visualizations of an environment. 

 

Providing precise awareness of what’s nearby in the work environment, such as people, vehicles and walls, UWB tags support machine operators in the mine, remote operators on the surface, and the navigation systems of self-driving vehicles. 

Radio network requirements for UWB tags

UWB tags require a mobile network or Wi-Fi network and a relatively dense network of anchor points within the mine. 

Accuracy, effectiveness and cost of UWB tags

UWB tags can deliver highly accurate real-time location tracking, even in challenging underground environments. These tags can pinpoint the location of workers and assets with centimeter-level precision. With short-pulse transmissions, UWB tags are designed to be energy efficient, with a battery life of up to 7 years. However, UWB systems require a more extensive investment in network infrastructure compared to other tag technologies. 

Pros of UWB tags:

  • Highly accurate real-time location tracking
  • Performs well in challenging underground environments
  • Provides centimeter-level precision for worker and asset monitoring 

Cons of UWB tags:

  • Requires ‌more complex and costly infrastructure
  • Power consumption can be higher than other tag technologies
  • Limited adoption and availability compared to RFID and BLE 

4. Virtual tag mobile apps

A virtual tag is an app on a smart phone.

Virtual tags are perhaps the most advanced and practical tag technology available to miners today. Virtual tag apps are designed to work with standard smartphone operating systems, so no specialized hardware is required to use the technology. Due to worker privacy issues, there has been pushback against the use of traditional tags in some regions. Older tag technologies such as RFID provide relatively low value to people working in the mine, as they can only be used to keep track of where personnel are located. 

 

In comparison, a virtual tag can provide staff with two-way communication and more tangible value. For example, tag apps can assist workers in navigating the mine and help ensure that they are not in harm’s way. Mass text messages, as well as push notifications that trigger staff phones to vibrate and flash, can support safety and evacuation protocols, creating a healthier workplace for everyone. 

Radio network requirements for virtual tags

Since smartphones can use Wi-Fi, cellular and Bluetooth radio technologies, connecting virtual tags and integrating them with other systems is relatively seamless. On the surface, GPS positioning can also be used. 

Accuracy, effectiveness and cost of virtual tags

Virtual tags are connected to backend servers via an IP session, so it's always connected. Any data detected by the virtual tag can be fed to the backend, increasing real-time situational awareness. 

By utilizing existing network infrastructure, virtual tags eliminate the need to install physical tags or beacons underground. There’s no need for dedicated tracking hardware, which reduces both upfront capital investment and ongoing operating costs. The technology can be updated regularly and improved based on user feedback, just like any consumer app. 

Pros of virtual tags:

  • Easily installed on widely available consumer devices
  • Eliminates the need for physical tags or beacons
  • Provides two-way communication and more value for workers 

Cons of virtual tags:

  • The cost of supplying workers with phones may be relatively expensive
  • Users must keep their device charged and with them at all times. 
  • Cybersecurity vigilance is required, as with any third-party software  

5. Bluetooth® Low Energy (BLE) beacons

Bluetooth® Low Energy (BLE) beacons are not tags themselves, but separate units installed in places where the network is poor, or where you need to improve location accuracy in the mine. Positioning tags read BLE beacons that act as reference points and then use Wi-Fi or cellular to communicate the BLE readings to a location engine that translates these readings into a position.

 

BLE is based on the same technology as Bluetooth classic, which is used to connect wireless devices such as headphones or your computer mouse. The BLE radio standard is designed to operate with minimal power needs, making it an effective technology for tracking in industrial settings. 

 

Once a tag is in range of a beacon, the tag’s unique identifier can be used to track the physical location of a person or machine in relation to the beacon. BLE beacons can also trigger location-based actions, such as sending a push notification or alert. 

Radio network requirements for BLE tags

BLE beacons use Wi-Fi or cellular to communicate readings A mesh network of BLE gateways or beacons may be required for comprehensive coverage within the mine.

Accuracy, effectiveness and cost of BLE tags

Bluetooth beacons relatively inexpensive and easy to install. The low energy consumption of beacons also supports cost savings and an overall smaller carbon footprint.

Pros of BLE tags:

  • Leverages ubiquitous Bluetooth technology 

  • Supports real-time location tracking and proximity monitoring

Cons of BLE tags:

  • Requires a more extensive network of BLE beacons (where you will need better accuracy)
  • Power consumption can be higher than RFID (battery power will last 3-4 years)
  • Obstacles and interference may affect performance

Epiroc supports the future of situational awareness in underground mining

Epiroc, a leading provider of mining equipment and solutions, is committed to supporting our customers' automation and digitalization journey. Mining companies can leverage our expertise, resources, and innovative solutions to implement the most suitable tag technology for site-specific requirements.

 

In recent years, Epiroc has invested heavily in expanding our portfolio of digital solutions, including advanced tag and tracking technologies. These solutions are designed to support the safety and productivity of miners, while also driving the industry towards a more digitized and connected future.

 

Epiroc partners with mining companies to support successful digital transformations. Whether you need help assessing your mine site, finding the most cost-effective solutions, or integrating technologies, we’re here to support you onsite, in the control room, and in the boardroom.

Underground mining Digitalization Safety Mining Article