Between the Poles

Using satellite imagery to prioritize vegetation management for utilities

A recent startup LiveEO is focusing on the digitalization of energy and transportation network assets using satellite imagery. LiveEO uses current multi-band imagery including radar and hyperspectral data at various resolutions from earth observation satellites to provide services to railway, electric power and pipeline operators.  The services include vegetation, third party encroachment, and ground distortion monitoring. I recently had the opportunity to chat with Sven Przywarra, co-founder of LiveEO.

Transmission line inspections are essential in ensuring grid reliability and resilience.  They are generally performed by manned helicopters often together with a ground crew.  There are serious safety issues when inspections are conducted by helicopter. Data may be collected with cameras and analyzed to detect a variety of conditions including corrosion, evidence of flash over, cracks in cross arms, and right-of-way issues such as vegetation encroachment. in North America annual inspections are mandated by NERC  and are not optional. With over 200,000 miles of high-voltage transmission lines and 5.5 million miles of distribution lines in the United States, improving the efficiency and reducing the risk of inspections would have a major impact on the reliability of the power grid. 

Vegetation is a significant source of outages for many utilities. In some regions from one quarter to one half of all outages can be ascribed to vegetation. Vegetation encroachment initiated the massive North American northeastern outage of 2003. It is so critical for utility operations that some utilities have a vice president responsible for vegetation management. It can be costly for utilities to identify areas of high risk vegetation encroachment. Previously I have blogged about an electric power utility in Brazil that used Airbus Pléiades satellite imagery combined with GIS data to identify high risk areas for vegetation encroachment in a power grid.

A recent startup LiveEO is focusing on the digitalization of energy and transportation network assets using satellite imagery. LiveEO analyzes current multi-band imagery including radar and hyperspectral data for vegetation, third party encroachment, and ground distortion monitoring. LiveEO uses multi-band imagery at various resolutions to distinguish vegetation and network assets, stereo imagery to estimate tree heights, difference detection to identify changes, and interferometry to detect subsidence and other ground distortions at the cm level.  LiveEO is developing its own inhouse training data for machine learning algorithms. 

For electric power utilities LiveEO applies machine learning multi-band satellite imagery from multiple sources to automatically identify areas of high risk for vegetation encroachment and fallover anywhere on the planet. The results of these analyses are available to clients over the web on handheld and other devices.  This enables follow-up ground inspections of areas of high criticality to develop pruning and other response programs. LiveEO has applied this approach to transmission as well as distribution circuits.  To demonstrate the wide ranging capability of their approach LiveEO is offering a demonstration of the analysis of 50 km of line anywhere in the world.

A number of companies, realizing that earth observation imagery in itself is of limited value, are not in the business of selling imagery, but the results of analytics applied to the imagery.  I have blogged about a new company GHGSat who use their own nanosatellite to estimate emissions from industrial plants, leaks from flow and gathering infrastructure in natural gas fields, and even livestock.  LiveEO is another example of a company who apply analytics to the huge amount of earth observation data to provide a valuable service that is safer and less expensive than the traditional approach to transmission and distribution line vegetation monitoring.

Scotland's system for sharing location information about underground infrastructure to be mandatory

Scotland is one of the leading jurisdictions in developing a nation-wide collaborative system for sharing information about the location of underground infrastructure among stakeholders involved in road construction including roads authorities, utility and telecom network operators, and Transport Scotland. The Scottish Vault system was implemented by the Scottish road works community on a voluntary basis in 2012 and will soon become mandatory. There is a dial before you dig system in Scotland, but it is being used less and less as network operators and roads authorities are switching to the Vault system.

Background

Underground utilities and other infrastructure are a major cause of highway construction schedule and budget overruns. In addition to construction delays, damage to underground utilities during construction makes every construction project a potential disaster site with risk for workers and the public. Every year, in excess of four million holes are dug in UK roads to repair assets, provide connecting services to new premises and to lay new cables and pipes. Failure to identify accurately the location of existing buried assets results in numerous practical problems, costs and dangers for utility owners, contractors and road users.  Location and attribute data on underground services can be very poor, in some cases especially for older assets even non existent. Improving mechanisms of integrating and sharing knowledge on utility assets and the location of street works are expected to lead to a reduction in the amount of street works in the UK by improving both the co-ordination of works and the quality of the information shared.

I recently had the opportunity to chat with Kat Quane, Road Works Policy Manager at Transport Scotland about Scottish initiatives to reduce underground utility damage.

Scottish Road Works Register

The Scottish Road Works Register (SRWR) is a system used by all roads authorities and excavators in Scotland to coordinate construction projects. For over 30 years, it has enabled them to share details of planned and ongoing construction projects including the location of underground infrastructure. Historically underground utility information has been shared by providing maps by email, websites, or distributed on CDs.

The Scottish Road Works Commissioner is an independent public official responsible to the Scottish Parliament. The Commissioner's aim is to improve the planning, co-ordination and quality of road works throughout Scotland.

Development of the Vault system

The Scottish Community Apparatus Data Vault (Vault) is intended to make underground asset information accessible to road authorities and network operators. organizations that have a statutory right to dig up in the public right of way. The participants in Vault are restricted to organizations that participate in the Scottish Road Works Register (SRWR) and have a statutory right to dig in the public right of way. In Scotland there are about 150 utilities, half of which have a statutory right to dig. The aim of the service is to allow timely access to information about all underground assets from a single centralized location to ensure the safety of workers in excavation as well as the public. Vault is funded as part of the overall SRWR funding.

The U.K. Mapping the Underworld (MTU) project, initiated in 2004 and largely funded by the Engineering and Physical Sciences Research Council (EPSRC) and involving the University of Birmingham, University of Bath, British Geological Society, University of Leeds, Newcastle University, University of Sheffield, University of Southampton, and UK Water Industry Research (UKWIR), sought to address the serious social, environmental and economic consequences arising from an inability to locate buried utility service infrastructure without resorting to potholing. As part of MTU initiative the University of Leeds developed the Vault system as part of the VISTA (Visualizing Integrated Information on Buried Assets to Reduce Street Works) project. The Vault system was adopted in Scotland in 2012.

The systems provider of the Scottish Road Works Register and Vault is a private company Symology. Data is provided by network operators and roads authorities via an extract, transform, load (ETL) process.  One of the objectives of Vault is to be able to integrate data in a variety of format from different GISs. The data in Vault not only shows the location of underground infrastructure but also the type of equipment such as gas, telecoms, electricity, water and others along with contact details for the owners of the facilities.

At a minimum utilities are expected to refresh their data four times a year. In Scotland there is no national statutory limit on as-built and update backlogs. For volatile data sources data is refreshed every 2 months. However, U.K. regulators may regulate this. For example, Ofgem requires as-built and update backlogs to not exceed 42 calendar days (30 business days).

Data protection

Scotland has a history of working collaboratively. This tradition has enabled utilities and telecoms to share details of planned works in the national register up to three months ahead of deployment. Non disclosure agreements have not been required in works planning – since everyone is subject to the same rules, and everyone can see everyone else’s data, no one is commercially disadvantaged. Road Works data recorded on the Scottish Road Works Register (SRWR) is available as open data. The SRWC is subject to public body rules on cyber security and all participants must meet the highest levels of data security.

The information accessible through Vault is only available to users of the Scottish Road Works Register.  The Scottish Road Works Commissioner has restricted access to the register to the roads authorities and excavators working in Scotland. Data is not shared with any third parties without the express prior permission of those that supplied the data. Access to the Vault system to contractors requires vetting by one of the members, either a network operator or roads authority. Access to the system is restricted by email and password. The system can be accessed from a notebook or a handheld in the field.

Incident reporting

Reporting underground utility damage is not part of the Vault mandate. Near misses, injuries and fatalities are reported to Health and Safety of the U.K. Government. For the last 30 years underground utility damage is reported to the “Road Works Register”. While reporting is not mandatory, since 2005 this register has been designated a legal document, and represents a permanent record that can be used in civil litigation to determine liability in the case of damage. Not all incidents of damage are reported, but it is likely that the more serious instances are. An annual report is published by the Scottish Road works Commissioner based on the data in this register, but number of incidents of underground utility damage is not reported, nor is the estimated costs of damage estimated. However the data is available and the number of incidents can be determined. Kat estimates that the number of incidents is in “hundreds”.

Data quality

There is currently no requirement relating to data quality on the data submitted to Vault by network operators and local government. However, the data submitted by utility operators and roads authorities in Scotland data is generally compliant with the U.K. data quality standard for locating underground utilities PAS 128 (2014). Furthermore, many utility operators including Scottish Water, Scottish Gas, and Scottish Power are making a concerted effort to improve the quality of the data that is submitted to Vault and Kat reports that data quality is improving. An important benefit of a system like Vault that enables all underground utility data to be seen in a single view and compared with what is exposed during excavation is that it makes inaccurate data very apparent. There is greater awareness of the value of reliable data for reducing the risk of damage during construction, planning and design, preventative maintenance and reducing liability costs.

Vault will soon be mandatory

In 2012 the Vault system was deployed in Scotland on a voluntary basis.  Last year a bill to make participation mandatory in Vault was passed by the Scottish Parliament and has received royal assent.  The COVID-19 pandemic has delayed implementation of the new legislation, but it is expected to begin as soon as the economy reopens.

This is a ground-breaking national initiative involving legislation, regulation, new technology and especially collaboration between stakeholders to address one of the chief causes of highway construction delays, cost overruns and injuries to workers and the public.  The Scottish Vault system addresses the challenge of sharing the location of underground infrastructure among stakeholders involved in civil construction projects and is an important step toward reducing the risk of underground utility damage.

Collaboration key to success of U.K. National Underground Asset Register pilots

At a Digital Leaders Virtual event Heath Pritchard, Maria Teneke, Holger Kessler and Neil Brammall of the National Underground Asset Register (NUAR) project reported on the progress to date of one of the Geospatial Commission's high profile projects.  In the context of bringing many stakeholders to the table, technically aggregating data from different sources and sharing the data over the web, the achievements are momentous; about 40 utility and telecom network operators and local government agencies have agreed to share data for two pilots, a harmonized data model and symbology have been agreed on, a prototype online system for sharing location data over the web has been developed and tested, and pilots in the North East of England and in central London have been completed using the prototype. At the event it was announced that an initial report of the NUAR project has just been released.

There are several reasons that the two pilots have been deemed a success; most importantly fostering a spirit of collaboration among the participants, but also limiting use cases to just four, implementing data protection measures and developing a prototype system that demonstrated significant value to the participants during the pilots.

Use cases

There are many potential use cases for location data about underground assets; reducing utility damage during construction, efficiency of planning, efficiency of engineering design, efficiency of construction, data interoperability,  emergency response, disaster planning, digital twins and strategic planning for smart cities to name a few.  The NUAR project team decided to focus on only four.

 

Use case	Value source	User need	Reason
Safe digging	Utility strike avoidance	Excavators need to identify all possible underground assets	So that users can dig safely without striking an underground buried asset
On-site efficiency	Project efficiency savings	Excavators need to identify underground asset data in a single integrated view	So that workers can easily and efficiently orientate themselves on site
Site planning	Project efficiency savings	Project planners need to identify the location and agreed attributes of all underground infrastructure assets	So that accurate and comprehensive plans can be made to avoid project delays
Data exchange	Data exchange efficiency savings	Asset owners need to share underground asset data through a central platform	So that asset owners can send and respond to data requests without maintaining their own data response systems/functions

Collaboration

Without a doubt the greatest challenge of the project thus far is bringing network operators and local government agencies to work together in a collaborative environment.  In 2018 Northumbrian Water brought network operators and local government agencies in Newcastle upon Tyne together at the Northumbrian Water Group Innovation Festival. The result was a collaboration with a common purpose where utilities, telecoms, local authorities and partners worked together to develop a combined infrastructure map for Newcastle including water, wastewater, gas, electricity, telecoms and other underground services. It  was reported that the event benefited from a spirit of cooperation which enabled local utilities, telecoms and local authorities to agree to share their data. A database was created in which each data owner remained a steward of its own data which was shared through a hub an available to all participants. At the festival a working prototype allowed participants to query the database and see all underground utilities on a single map.

System architecture

Neil Brammall described the system architecture used for the prototype.  Its key features are that it supported live links using APIs and ETL processes for accessing network operators' and local authorities' data  and it provided a web user interface to users for accessing and displaying location data and providing feedback. In response to a question Neil said that the pilots did not prove the value of providing an API in addition to a user interface for users to access the data and the jury is still out on whether this capability will be a requirement.

Data quality

There were no data quality requirements for the data submitted by network operators and local authorities for the pilots.  I had the opportunity to see the system in action in downtown Newcastle and to compare the location of underground utilities with facilities visible above ground.  What I saw verified what I expected, in much of the world there are data quality issues in network documentation and records.  Neil emphasized that there is no silver bullet for resolving data quality issues.  He suggested that NUAR can contribute to improving data quality by bringing attention to data quality issues and by promoting the benefits of better data quality. I would expect that a capability analogous to the "observations" feature of the prototype which enables feedback from workers in the field to be easily passed back to NUAR, network operators and local authorities will play a key role in improving data quality in the long term.

Data protection and security

A risk-based legal approach to data protection and data sharing security has been a major milestone for the pilot projects.  From a security perspective the prototype system adhered to strict security standards and audit controls set by the Centre for the Protection of National Infrastructure (CPNI), and the National Cyber Security Centre (NCSC) as well as OS guidelines. In addition it had to protect competitive information, for example, by restricting the size of areas for which data could be requested and by limiting the number of requests from individual users. This attention to data protection was key in achieving what has not been possible in previous projects with a similar objective - all 35 public and private sector organizations participating in the pilots signed data sharing agreements after review by their legal departments.

Demonstrating value

An important success factor from the initial Northumbrian Water Festival through the two pilots was the rapid development of a prototype system that allowed participants to experience the benefits of access to shared location data. The prototype, which was developed by the Ordnance Survey, enabled data to be ingested from many different sources, mapped onto a harmonized data model (developed together with the Open Geospatial Consortium MUDDI initiative), visualized on a single map with a common symbology, and made accessible over the web.  The system was simple to use and could to accessed from handhelds the field.  

Also important from the perspective of engagement was an additional feature which enabled feedback from the field.  Referred to as "observations", this feature enabled workers in the field to contribute field notes such as inaccurate location or incorrect type of equipment or manufacturer, as well as report on the condition of the equipment such as serious corrosion, damage, leak, and other issues.  During the Digital Leaders Virtual session this feature and other capabilities of the prototype were demonstrated by Holger Kessler. 

Another key success factor of the pilots was immediate real world testing.  Providing participants with access to shared data with minimal bureaucracy proved crucial in maintaining trust and buy-in.

Anecdotal feedback from participants in the pilots has been positive. The NUAR team is working on identifying and quantifying benefits to help build the evidence case for any future national rollout plans.

Next steps

Over the summer the NUAR team will be conducting additional work with utilities and local authorities in the North East of England and in London to help refine the requirements for a national system.  To ensure any future system is fit for purpose, the NUAR team will continue to engage with asset owners and local authorities in the north east of England and London, in particular, reaching out to independent network and distribution providers as well as district heating operators to better understand their data and their willingness to participate.  In response to a question Maria Teneke said that the team will be following a robust commercial process based on UK government procurement guidelines and will be interacting with the market prior to any invitation to tender.

Digitally capturing the location of underground utilities detected using electromagnetic techniques

The industry standard for locating underground utilities is a manual process involving the use of an electromagnetic (EM) wand to detect underground cables and pipes.  The detected location is typically recorded by painting or otherwise marking the ground.  I recently had the opportunity to chat with Kieren Tinning of Terraflow Geomatics, whose Utility Mapper product adds significant value to an industry standard underground locating tool by enabling the digital capture of the location of underground pipes and cables detected with an EM wand and the generation of 3D data for integration with CAD and GIS applications. On a recent depth of cover survey of a thousand kilometre gas transmission line it was found that because Utility Mapper automated most of the data capture and geoprocessing staff time was reduced by 42 %.

Background

In the U.S., underground utilities are a major cause of highway construction delays. Knowing where things are underground has become important enough that in several countries around the world - France, the Netherlands, Singapore, and the U,K., initiatives are already underway to create national digital twins of above and below-ground infrastructure. Recently there have been important technical advances in several areas that are have brought the feasibility of cost-effective mapping of underground infrastructure at the municipal, regional, and national level within reach.  One of these is to digitally capture the location of underground utilities detected using remote sensing technologies such as electromagnetic (EM) and ground penetrating radar (GPR).

Remote-sensing tools for underground utility detection have been available for decades. Electromagnetic (EM) detection wands can be used in several different ways. Passively detecting utilities with EM is used for services that emit naturally emit a frequency such as electrical cables (50 or 60 Hz).  Another approach is to physically connect a signal generator to a service.  This method requires physical access to the service, usually by way of a surface feature that is connected to the service such as a valve. Another technique is to introduce an active signal into a line through electromagnetic induction (EMI). The advantages of EM detection are that it is simple to use and effective for detecting conductive underground infrastructure.  Ground penetrating radar is an alternative technique for underground detection, but in some soil types such as aggregate and clay GPR does not perform well. Without supplementary information GPR does not identify the type of utility (gas, water, electric, fiber optic). In addition GPR requires an expert, typically a trained geophysicist, to interpret the scans. As a result EM detection has become the industry standard.

One of the serious deficiencies of EM is that most wands do not permit the digital capture of the location of detected underground objects.  Typically EM detection is a manual process in which the location of underground infrastructure is recorded by painting or otherwise marking the ground.  Terraflow Geomatics' Utility Mapper changes this by enabling the digital capture of the location of underground pipes and cables detected with an EM wand. Using together RTK devices such as Trimble's Catalyst enables highly accurate location information to be simultaneously captured.  Terraflow's Data Engine automates the synchronization of this data back to the desktop for integration with AutoCAD, Microstation,  ArcGIS and other applications.

Customer experience

PVS Contractors performs large scale depth of cover and other locate services for pipeline operators. Prior to acquiring Utility Mapper, calculating the depth of cover was a manual process in which the depth was recorded manually and correlated with the GPS location. For a survey of a thousand kilometre pipeline, this typically would require eight full time staff for eight months, plus an admin staff member and supervisor for several days per week to check and confirm the data. For a recent large scale depth of cover survey for a gas transmission pipeline running from Windsor to Montreal, about a thousand kilometres, PVS deployed Utility Mapper together with Vivax-Metrotech electromagnetic locators and Trimble Catalyst, which enabled survey-grade positioning with an Android smartphone.  Utility Mapper automated most of the capture and processing - integrating the GPS and electromagnetic locate information and wirelessly synchronizing the location and depth of cover information directly to ESRI’s ArcGIS Online for quality assurance and quality control. This reduced staffing requirements from 64 to 47 person-months. Furthermore, the Utility Mapper solution reduced the data review time for a supervisor (prior to sending the data to the client) to one hour per week .

Summary

Terraflow's Utility Mapper is an important advancement.  It adds significant value to the industry standard EM underground utility locating tool by enabling the cost-effective digital capture of 3D location data captured by EM devices and RTK GNSS and streaming this data to users' CAD and GIS applications.

Survey delineates subsurface utility engineering (SUE) adoption in Canada

The Centre for Advancement of Trenchless Technologies(CATT) has just released the report of a survey designed to better understand the current state of subsurface utility engineering (SUE) practices, barriers, and acceptance across Canada.  The most important conclusion of the survey is that most organizations rely on as-built records (which are frequently inaccurate) and surface site inspections (which can only infer the location of most underground utilities) for underground utility location information.  Furthermore, this information is used primarily during the construction phase of a project, not during planning and design, when accurate underground utility information has its greatest value. It was found that many organizations still do not update or request reliable as-builts during construction projects. The survey found that for most organizations SUE is conducted on a project-by-project basis, instead of being a standard process as part of construction projects. 

The target audience for the survey included infrastructure owners, consultants, contractors and technology providers – the main stakeholders in the SUE industry.  84 % of respondents were from Ontario with the remainder from other provinces.  46 % of respondents were infrastructure owners, and 43% engineering consultants.  70% of the infrastructure owner respondents represents large municipalities. More than half of the respondents had five or more years of experience with SUE on construction projects.  The remainder reported one year or less of experience with SUE.

Analysis

The survey revealed that Quality Level D (as-builts and other records) and Quality Level C (surface site inspections) comprise the most frequently used information about the location of underground utilities.  Only 15 % of respondents regularly used more reliable Quality Level B (remote detection) data during the planning phase of construction projects and less than a third used remote sensed data during the design phase.  For those using remote sensing technologies, 79% reported using electromagnetic methods, 16 % ground penetrating radar, and 15 % magnetic methods.

Two thirds of infrastructure owner respondents reported that their organization requires combining as-builts into their records or GIS system and about the same proportion reported updating their records database during construction.  But 59% said that they do not periodically review, verify and update utility records.  Very few of these, only 4%, said they are planning to implement a SUE program.

Almost all of the respondents (87%) were aware of SUE and many (70 %) had some SUE experience.  59% of the respondents were aware that SUE reports and drawings need to be stamped by a professional engineer (P.Eng.) or Professional Geoscientist ( P.Geo.).

Respondents were asked about their familiarity with standards relating to underground utility information including CSA S250 Mapping of Underground Utility Infrastructure, TAC Guidelines for the Coordination of Utility Relocations, ASCE 38-02 Standard Guidelines for the Collection and Depiction of Existing Subsurface Utility Data, CSA Z247-15 Damage Prevention, or ISO 15489-1:2001 Information and documentation — Records management.  Less than half of survey respondents reported awareness of some of these standards.  The best known standards were CSA S250, ASCE 38-02 and TAC Guidelines.  Very few respondents were aware of ISO 15489-1:2001.

Using statistical averaging to increase depth of penetration for ground penetrating radar

Recently Greg Johnston of Sensors and Software gave a very informative webinar on the factors that limit the depth to which ground penetrating radar (GPR) is effective in detecting objects.  Greg showed how statistical averaging ("stacking") can be used to increase the signal to noise ratio and substantially increase, even more than double, the depth to which objects can be reliably detected.

The frequency of the radio waves used in GPR is an important determinant of the depth to which GPR is effective. The lower the frequency, the deeper radio waves reach. But there is a trade off, because the lower the frequency the lower the resolution of what is detected. Also the lower the frequency the longer the radar antennas required which can stretch to 8 m at 12.5 MHz to 1 m at 100 MHz to 7 cm at 1 GHz.  For example, while a 400 MHz signal may detect objects down to 25 cm, objects less than 6.25 cm in size may not be resolved. Furthermore the deeper the object, the more the radio waves are attenuated, and it may not be possible to resolve objects 5-6 cm in size at depths below 50-60 cm.

GPR can use frequencies in the range 10 MHz to 2 GHz, but typically the frequencies used by commercial products are in the range 100 MHz to 1000 MHz. The webinar focussed on 100 MHz, but the principles determining the depth to which GPR is effective apply to just about any frequency. Because of the low resolution of low frequency GPR, it is not typically used for detecting underground utilities which can often be small diameter cables and pipes lying fairly close to the surface. But for geological investigations, large scale archaeological research or scannng for large underground utilities, low frequency GPR is often the best choice.

According to Greg, the three most important factors determining how deep GPR is effective are

• Electrical conductivity of the soil
• Power of the GPR radio transmitter
• Background RF noise

Electrical conductivity

Radio waves do not penetrate far through soils, rocks and most man-made materials such as concrete. The most important external factor determining the depth achievable by GPR is the electrical conductivity of the subsurface material. For example, while radio waves only penetrate a few millimetres in salt water, they can penetrate 100 metres in granite.

Transmitter power

The FCC in the U.S. and other organizations in other countries limit the power of radio waves emitted by untrawide band devices into the atmosphere, but do not place restrictions on transmissions into the ground. By using shielding to prevent emissions into the atmosphere, the power of the radio transmitter can be increased and greater depths achieved.  But this is difficult to achieve at low frequencies and is not a viable way to increase the effective depth.

Radio frequency noise

A major problem when using very sensitive RF antennas is that they pick up noise from other sources such as radio and TV stations, walkie-talkies, and cell phones. Some of these are not random ("coherent external signals"), but most of these are random and comprise background noise. Increasing the ratio of the signal reflected from underground objects to background noise allows weaker signals to be detected which increases the depth to which GPR is effective.

One way to increase the signal to noise ratio is to use statistical averaging. Repeatedly scanning the same area and then averaging the results effectively averages out the background noise and accentuates the signal reflected from underground objects. While one scan may limit the effective depth to 1.8 m, averaging 256 scans can extend the depth to 3 m. This process is referred to as "stacking". Stacking reduces the noise level, increases the signal to noise ratio, and increases the depth of penetration. To take advantage of stacking, the essential technology advance is being able to capture multiple scans rapidly. Sensors and Software's NOGGIN Ultra 100 is able to capture and average between 256 and 65,000 scans. The speed at which the GPR device is moved determines the maximum number of stacks. The DynaQ software implemented on the device automatically calculates the stacking level based on the speed at which the device is moved. A speed of 0.2 km/hr will allow the maximum 65000 scans. For a faster speed the software will limit the number of stacks which reduces the detection depth.  Greg gave an example where the effective depth was increased from 5 m to 16 m in sandy soil.

A complicating factor is coherent external signals that are often generated by the GPR device itself. An important technical requirement for a GPR device to be effective at greater depths is that it needs to be "quiet" with respect to extraneous RF emissions.

Statistical averaging has been used in other fields such as seismic exploration for many years.  For underground utility detection it has been discussed for years, but until recently technical limitations on the speed of sampling have prevented the development of practical devices and software implementing this technology.  Now devices and software implementing stacking technology and available from Sensors and Software and other vendors are enabling more efficient, cost effective, and reliable 3D mapping of underground infrastructure using GPR.

White paper on reducing damage to underground utilities during construction

It is estimated that unreliable location information about underground infrastructure represents a $50 billion drag on the U.S. economy. Comparing the United States and Japan reveals a startling difference in the annual incidents of underground utility damage during construction - over 400,000 incidents in the U.S. and less than 150 in Japan. Clearly something can be done to reduce underground utility damage. Important advances in technology now make it possible to capture ground penetrating radar scans at highway speeds; simultaneously capture of above and below-ground scans using LiDAR and GPR to create a complete pre-design survey; generate centimetre accurate as-builts from a video taken with an Android smartphone; map underground pipelines for upto two km using inertial locating; detect underground objects 30 feet deep with acoustic sensing; and integrate existing 2D and site investigation results in a 3D model visualized in augmented reality. On-line systems for sharing information about the location of underground infrastructure have been implemented to manage underground utilities in the public right of way. 

Many jurisdictions in the Americas, Europe, and Asia Pacific have implemented policies and organizational structures for capturing and sharing information about the location of underground infrastructure.  Statistics reveal that a comprehensive approach involving policies, technologies and construction practices is required to be successful for continuing improvement in reducing utility damage during construction. Based on a review of international initiatives for managing location information about underground infrastructure, a set of 25 recommended elements have been compiled that should be considered by anyone intending to to reduce the risk of underground utility damage during construction.

A white paper prepared by Geoff Zeiss and Dr. Sakura Shinoaki and published by the Geospatial Information and Technology Association entitled Reducing Damage to Underground Utility Infrastructure during Excavation assesses costs, benefits, technical advances, and case studies to develop 25 recommendations for reducing damage to underground infrastructure. The white paper can be downloaded for free here and a summary is available here.