Solution Summary: Geospatial Augmented Reality System
Unlike other types of infrastructure, underground cables are difficult to accurately locate, and every year several accidents happen due to mislocated or unmarked utility cables. Various geophysical technologies have emerged to assist in investigating underground utilities, although none by itself can provide a complete and comprehensive solution for locating underground cables in all types of soil. This solution aims to minimize the risk involved in ground penetration work, which can expose workers to inadvertent contact with underground cables. It sets out a combination of technologies, including augmented reality, geographic information system (GIS), sensors, geospatial databases of subsurface utilities, and mobile applications, to obtain as much information as possible about underground cables before any excavation and ground penetration work begins. This solution may help to ensure that the work is performed safely.
There are geophysical technologies (e.g., ground penetrating radar, electromagnetic techniques, etc.) that can assist in locating underground cables. Each technique mentioned is effective for a specific scenario, but may be less effective for others. Although there has been tremendous development in the field of cable-locating technologies over the past years, each one may be flawed and incomplete. Thus, a new technology that can combine all existing technologies through a multi-sensory approach may give more accurate results in locating underground cables. In the following, a brief description has been provided for available multi-sensory technologies for locating underground cables.
Proximity Alert System detection technology:
This system utilizes multiple technologies such as RFID, GPS and near-field electromagnetics to detect underground utilities and prevent collision. This system provides alerts and warnings when excavation equipment approaches underground cables and also provides latitude and longitude coordinates of cable locations. It can enhance an operator's situational awareness and enable a safer and more productive work environment.
Figure 1. Proximity Alert System (PAS) for underground utilities (Source: http://www.http://pbegrp.com)
The software for a smartphone or tablet connects to a GIS web server. This technology can request geographic asset data from the server and display it on the mobile device. The output can be viewed as a map, text or 3D visualization. All asset information (poles, cables, etc.) can be viewed through the device. Moreover, the asset data can be edited directly by the user and updated immediately for future use (Figure 2).
This technology can display – on top of the real-time video – a 3D model of an asset that may be obscured in the real world. Using this technology, cable locations can be pre-marked before actual excavation occurs and can improve a worker’s awareness of the surrounding environment without having previous knowledge and information before starting excavation activities.
Figure 2. Augmented Reality Mobile GIS (Source: http://www.augview.net)
- Reduce administrative costs due to delays, incomplete information, and human error
- Deliver up-to-date and easy-to-read underground cable data information
- Enable viewing of data from different GIS systems and interactive maps simultaneously
- Increase the accuracy of data through a spatial update
- Lower usage cost since there is no need to purchase other imagery data feeds, and it is supported by multiple devices and platforms
- Work in both offline and online mode.
Geospatial Augmented Reality System:
This approach creates geospatial augmented reality (AR) to visualize and monitor the proximity between underground utilities and equipment. This technology enables knowledge-based excavation by providing the 3D spatial context of underground cables in the vicinity of an operating excavator. This information is accessible to the excavator operator and the on-site spotter, and includes the location, type, and any anomaly of utilities that exist in the vicinity of the excavator (Figure 3).
Figure 3. AR visualization of underground cables (Source: Adapted from Talmaki et al. 2010)
Figure 4 depicts the major components of this system: geographic information system (GIS), augmented reality (AR), real time kinematics (RTK) precision global positioning system (GPS), and telemetry, all of which help the operator visualize and monitor the proximity of the excavator to the buried cables.
Fig 4. Data flow for collision avoidance system using augmented reality (Source: Adapted from Talmaki et al. 2010)
This technology provides more advantages, such as:
- Visual guidance for digging activities
- Utility network planning
- Location of hidden utility assets
- Location of hidden spots of cable damage
- Onsite instruction of technical staff
- Visual guidance for technical facilities
- There is a critical need to update the information as necessary to help create a 3D model of underground cables and then project it to a real-world view. Updated information about cable locations can be converted into a format that is accessible, easy to use and understand, interoperable, and always updated.
- Since most of the time, the as-built data does not accurately indicate the actual location of cables, active real-time sensing can be used in conjunction with as-built data for more accurate locating. But this is something the as-built or old datasets cannot avoid completely and will lead to less than optimal results. (As-built drawings are a revised set of drawings submitted by a contractor upon completion of a project. But most of the time the as-built drawings of underground utilities in both horizontal and vertical locations are completely different from what actually exists beneath the surface.)
- The capability to always have access to real-time information is challenging and will make it difficult to remain competitive and respond quickly to daily and frequent demands.
- No single technology can detect all underground utilities in all soil conditions.
- Adding GPS to these multi-sensory technologies introduces errors and reduces the accuracy but using Kinematic (RTK) GPS can provide better accuracy.
Electrical hazards are among the main construction industry hazards that cause serious injuries and death. The Bureau of Labor Statistics reported the number of fatalities in electricians increased by 14 cases in 2014 to 78 (BLS 2014). Electricity can cause electric burns, electrocution, shock, arc flash/blast, fire, and explosions. Electrical hazards may happen due to failure to detect the accurate location of cables before construction site excavation, jack hammering, well drilling, landscaping, trenching for piping and fence installation – all of which can lead to accidental contact with power cables, resulting in electrocution, shock or burns (Figure 5). The annual cost of accidents due to hitting utilities during the excavation process is estimated to be more than a billion U.S. dollars (Spurgin et al. 2009). Excavation-related accidents account for nearly one-third of all incidents related to utilities (Talmaki et al. 2010). Thus, paying attention to underground cable location technologies can make for more accurate and safer excavation processes. The risk of working near cables must be assessed and controlled.
Figure 5. Examples of earthworks causes of electrical hazards
How Risks are Reduced:
Hitting utility lines can create physical danger to construction workers, interruptions to the daily lives of people who depend on the utility, and danger to nearby buildings. All these lead to excessive costs, not to mention deaths and injuries. Using this new technology will drastically change the way underground cable locations are mapped.
Using this technology helps prevent excavator-underground cable hits and avoids damages to existing underground cables due to unknown or erroneous locations of utilities. This combination of various technologies can give comprehensive information to the excavator about the location, depth and other attributes of underground cables and can alleviate problems that have occurred with previously used approaches. Therefore, using this technology at jobsites can improve safety and accuracy in the excavation process. Moreover, it can clarify the relationship between aboveground structures and underground infrastructure in order to respond to the risk of accidents associated with excavation.
Effects on Productivity:
Even hitting and making contact with less dangerous utilities can cause various risks and damages, which may result in huge costs and reduced productivity. This new technology can be seen as transformative rather than destructive because it often increases productivity by eliminating or minimizing the risk of hitting underground cables in excavation activities. It can help to reduce operational overhead and is accessible to all workers since they all carry their mobile devices every day. This process does not require extensive and time-consuming paperwork and can do the same job more effectively. Advances in these types of technologies can improve efficiency, result in greater cost-effectiveness and diminish physical waste. As advancements continue in this area, these types of systems not only enhance what electrical contractors can do, but also cut down the associated time and cost.
Behzad Esmaeili, Ph.D. - University of Nebraska- Lincoln
Sogand Hasanzadeh - University of Nebraska- Lincoln
Pouya Gholizadeh - University of Nebraska- Lincoln
Erik Bruening - University of Nebraska- Lincoln
Brett Farquhar - University of Nebraska- Lincoln