Home Blogs Centimetre-accurate as-builts efficiently captured with a smartphone

Centimetre-accurate as-builts efficiently captured with a smartphone

Without accurate maps of underground infrastructure, every construction project has the potential to become a disaster site. Incidents of underground utility damage are more frequent than many people realize. In the U.S. there are between 400,000 and 800,000 incidents every year. Over the past two decades in the U.S. there have been over 400 fatalities and nearly 2000 injuries attributed to hitting underground infrastructure during excavations. Inaccurate and missing information about underground infrastructure is also responsible for construction project schedule and budget overruns. According to the Federal Highway Administration (FHWA) missing or inaccurate location information about underground utilities is a major source of highway construction project delays. The drag on the U.S. economy resulting from underground utility damage is estimated at $50 to $100 billion annually.

90% of underground utility damage during construction is attributable to (1) incomplete, inaccurate and out of date records maintained by utilities and telecoms and (2) data format issues including paper, digital ink (pdf) and raster (imagery) records. As one customer said, existing records are typically 15-30% off the mark. Another contractor reported that records are not updated after relocation of assets. The result of these and other issues is that excavators are often working blindly.

Also Read: Role of GeoBIM in Clash Detection

AVUS is a recent startup that has been incubated by Vinci Group , a French construction company with annual revenue of €48.1 billion. In 2019 Vinci ran 290 000 construction worksites. AVUS is a service company providing services for capturing accurate as-builts and visualizing underground infrastructure.   Recently I had a chance to chat with Sebastien Magat, the entrepreneur behind AVUS.

As-built service

AVUS have developed a reality capture solution that allows the creation of as-builts accurate to ± 5 centimetres from a video taken with an Android smartphone. Currently in use at 30 construction sites, the workflow is very simple; open the AVUS app on a smartphone, connect to a local RTK base station or use known control points, enter project and site information, use the app to create a video by walking along the open trench after installation of the utility, upload the video to the AVUS cloud site where a point cloud is created, georeferenced and scaled using RTK or known or recorded ground control points, and receive the as-built in the form of point cloud (.las), orthophoto, and CAD drawing (.dwg). A similar process can be used with utilities exposed during construction to amend and correct existing records.

The process of generating a DWG file from the point cloud is currently a manual process, but with the rapid advances in feature extraction technology, aided by machine learning algorithms and the compilation of training data by EPRI and others, in the future this process is expected to be increasingly automated.

A benefit of the AVUS as-built services is that it provides reliable records of underground infrastructure certified to ±5 centimetres horizontally and vertically. For new infrastructure this provides a reliable record of what was installed in the ground, in other words, “as-constructed” instead of “as-designed”.  For existing infrastructure this enables discrepancies and omissions to be reported back to asset owners. The as-built records are PAS 256 compliant and integrate with existing utility GIS databases.

Another important benefit of the AVUS as-built service is that it does not add significantly to construction costs. It is very efficient compared to the time required to call a surveyor to the site – the AVUS video recording takes less time than it would take for the surveyor to drive to the site. Furthermore, the video approach works in every weather condition, even at night in artificial lighting. This enables the construction crew to continue with their work, instead of having to wait for the surveyor to get to the site and conduct the survey.

Augmented reality

AVUS compiles existing 2D and 3D records and site investigation results into a 3D model that can be visualized in augmented reality on a handheld.  An Android app has been developed that uses Google AR Core to project highly accurate holograms on a smartphone. Accurate positioning is achieved by connecting to a local RTK base station or by calibrating to known features in the field of view.

The app is easy to implement and use and it integrates with existing utility GIS databases. The benefits of this AR approach is that increases productivity by enabling more rapid location of underground networks and results in reduced risk of underground utility damage.

AVUS provides an important service that captures the location of underground infrastructure efficiently, improves the quality of location data, and makes the data easily accessible to engineers and contractors in an augmented reality view in the field.

This article was originally published on Between the Poles