New Measurement Tool to Validate Wireless Communications and Tracking 

Radio Signal Coverage in Mines 

Objective 

The objective is to develop a tool to accurately 

measure, store, and plot on a mine map the radio signal 

strength of wireless communications and tracking systems 

in underground mines. This capability would allow mines 

to identify areas where radio signal coverage may be weak 

or missing, enabling them to correct these coverage gaps 

before an emergency occurs. 

Validating Radio Signal Coverage in Mines 

In June 2006, Congress passed the Mine Improvement 

and New Emergency Response (MINER) Act, mandating 

that underground coal mines provide emergency response 

plans that include two-way wireless communications and 

electronic tracking systems within three years. Since that 

time, most underground coal mine operators have installed 

these systems using guidelines set forth in the Mine Safety 

and Health Administration (MSHA) program policy letters 

(PPL) that followed. 

Depending on the size and complexity of the mine, the 

process of verifying the actual radio signal coverage of 

communications and tracking systems can be difficult and 

time-consuming. The only way to ensure coverage is to 

perform many manual radio signal “spot checks” while 

walking to different locations throughout the mine, thus 

verifying two-way communications with the surface. This 

is a crude way to ensure the overall dynamic coverage of 

an emergency communications and tracking system, and 

this procedure only verifies coverage in those areas that 

have been checked. To address this problem, the 

MineComms MapperTM (MCM) was developed under a 

National Institute for Occupational Safety and Health 

(NIOSH) contract in 2009 by Helium Networks. The 

MCM (Figure 1) provides a faster, more comprehensive 

approach for verifying communications and tracking 

system signal coverage in underground mines. 

Figure 1. MineComms Mapper (MCM) being towed in a mine. 

Background on the MineComms Mapper 

In searching for a better method to map radio signal 

coverage, NIOSH researchers recognized the need to 

develop a mobile tool to determine the position 

coordinates at any location in the mine, measure the radio 

signal strength at that location, and record the data for 

future processing. The MCM uses an Agilent N9340A 

spectrum analyzer (see Figure 2) to scan signal 

frequencies for communications and tracking systems 

ranging from 100 kHz to 3 GHz. With a mine map overlay 

(e.g., AutoCAD) loaded into the computer, the MCM can 

No. 544 October 2011 
Figure 2. Inside the MineComms Mapper. 

indicate the signal strength for any location through which 

it travels. The MCM was also designed to fit through 

mandoors measuring 2 feet by 2 feet for maximum 

portability underground. 

The primary method of location tracking by the MCM 

uses two rotary wheel-turn encoders designed for accuracy 

over long distances. To complement this tracking system, 

the MCM also employs micro-electromechanical systems 

(MEMS) technology for inertial navigation to determine 

the cart’s location without any fixed external references. 

The inertial technology is used when the MCM turns 

sharply and its wheels slip, causing false position 

measurements. 

The MCM has rubber tires so it can be attached to any 

haulage vehicle and towed for long distances. Therefore, a 

mine consisting of many miles of tunnel can be covered 

much faster when compared to the time required for 

manual “spot checks” of two-way communication with the 

surface. Further, the automated data accumulation 

minimizes human error associated with conventional 

methods of measuring communications or tracking 

coverage. 

NIOSH Evaluation of the MineComms Mapper 

The MCM was delivered in 2009 and NIOSH has 

evaluated it in underground mines for radio signal data 

gathering and storage. For a mine covering several miles, 

the survey time was significantly less than that required 

using manual methods. In one test, the MCM collected 

2,643 data points covering a distance of over 3,000 feet in 

about 19 minutes (about 2.3 samples per second). Also, 

because the survey data were electronically entered in the 

database, there was no chance for human error and the 

MCM’s location was automatically calculated. 

The software that drives the MCM takes measurements 

of both position and signal strength and joins them using a 

timestamp. The information is then stored in a database 

that can be exported to a spreadsheet for easy analysis. 

Once the data are exported from the database, they can be 

displayed in a variety of forms to produce clear 

representations of system performance. The mine operator 

can see exactly where the communication system’s 

coverage problems are underground, in real time, and can 

also retain the raw data for long-term comparisons.

Figure 3 shows an example of a map created from data 

generated by the MCM, representing the range of radio 

signal coverage in a particular mine. The MCM offers a 

variety of preset programs that can be applied to most 

common communications and tracking systems being 

installed under the MINER Act, including leaky feeder, 

900-MHz node-based, medium-frequency, and Wi-Fi 

systems. Each MCM is customized by the manufacturer 

for size, weight, and frequency spectrum. 

Figure 3. Mine communications coverage map with data generated 

from the MCM.

For More Information 

For more information on the MCM and its use, contact 

Nicholas W. Damiano (ndamiano@cdc.gov) or the Health 

Communications Coordinator (OMSHR@cdc.gov), 

NIOSH Office of Mine Safety and Health Research, P.O. 

Box 18070, Pittsburgh, PA 15236-0070. 

To receive NIOSH documents or for more 

information about occupational safety and health topics, 

contact: 1-800-CDC-INFO (1-800-232-4636), 1-888-

232-6348 (TTY), e-mail: cdcinfo@cdc.gov, or visit the 

NIOSH Web site at http://www.cdc.gov/niosh

Mention of any company name or product does not 

constitute endorsement by the National Institute for 

Occupational Safety and Health.

DHHS (NIOSH) Publication No. 2012–100