Real-time location sensing (RTLS) describes a range of technologies for locating an asset or resource—from radio frequency-based approaches to determining distance by measuring the difference between fixed anchors of beacons/tags that are affixed to personnel, equipment and materials.

RTLS is ubiquitous in society (e.g., GPS is found in equipment telematics, surveying hardware and personal smartphones). In the construction industry, there’s an emerging trend of applying RTLS to other forms of asset and resource management, and to support workflows such as labor productivity tracking, materials management, and worker health and safety.

RTLS Technology Overview

RTLS comprises a combination of different hardware components.

Beacons or tags: a mobile device that’s enabled with location-sensing technology.

Location sensors or anchors: devices of known or fixed position that use radio frequency (RF) technology to determine the relative location of the tags as they move within an area of RF coverage.

The location engine is the software that communicates with tags and sensors to determine the location. The location engine reports this information to middleware and finally the business application.

It’s important to understand which RF approach enables the technology solution, as this directly correlates with the ability to determine location, accuracy and the ability to respond to construction jobsite conditions. The underlying RF approaches involved in RTLS include:

• proximity (RFID, closed-circuit TV, photogrammetry);
• time of arrival;
• angle of arrival;
• time difference of arrival;
• time of flight; and
• received signal strength indicator.

Location reporting is critical because it dictates whether the data will be actionable and accurate enough to support the desired objectives.

RTLS hardware selection is a key element of both accuracy and dependability of a system, but it also has a significant impact on cost. Understanding the system specifications and the differences between vendors that supply them is essential.

Middleware is the software that resides between the pure RTLS components (the tags, the location and the location engine) and the business application that delivers value from the technology.

Middleware provides the messaging, routing and connectivity features required to integrate data into business applications. As construction applications become increasingly connected, contractors pursuing an RTLS strategy must ensure that data can be shared within their existing tools to support management workflows and derive maximal business value.

Finally, the application is the software that performs the work the users are interested in. Assuring that the application fits the specific construction management needs is critical. Because RTLS is still emerging in the industry, the available applications are still relatively limited.

In the context of construction, the intersection of middleware and the application is where RTLS can become challenging. Combining these different elements in the highly dynamic and specific settings of a construction project can be incredibly difficult to achieve in practice.

Potential RTLS Application: Labor Productivity Monitoring

The first area RTLS can help with is productivity. Activity sampling is the process of observing a work process, recording what work was ongoing and whether personnel were productive or not. While helpful, this typically documents one work area for a day, which limits scalability. One person can’t watch every work area, every day.

RTLS provides the ability to document actual site conditions and delivers data that informs planning, scheduling, resource allocation and the location of assets. If location data can be integrated into management workflows to serve as an indicator of planned versus actual conditions, it can help identify areas requiring attention that would be impossible to measure manually. (See charts above for examples of personnel location and movement in a construction prefabrication activity).

Construction projects are highly dynamic environments. Workforces move as the project progresses, and personnel, equipment and materials are, for the most part, dynamic resources.

Project planning and scheduling require a level of understanding around the location and movement of resources. Firms can assume that their crews, equipment and materials are where they’re needed, when they’re needed, but it’s almost impossible to measure these variables without some form of passive location-sensing technology.

By providing real-time situational awareness of the location and motion of assets, and using this data to make better decision, RTLS has the potential to improve construction management.