Modern reality capture technology is not only providing a high accuracy alternative to paper as-builts, but is also being used to capture the location of underground utilities and other infrastructure exposed during during excavation or exploratory digging. LiDAR scanning or taking photos or videos with a handheld together with high accuracy GNSS equipment such as RTK or accurately surveyed control points makes it possible to achieve survey-grade accuracy for underground utility infrastructure without a survey team on site. In France a new commercial GéoCassini cloud service is available from e-Cassini that captures, processes, integrates with GIS and other geodata sources and shares accurately georeferenced point clouds of underground utilities. Furthermore the e-Cassini MarketPlace enables customers to publish and market their data stored in a GéoCassini database to the broader construction community.
Background
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 500,000 and 800,000 incidents every year. Every year there are injuries and fatalities attributable 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.
Utilities have used LiDAR and photogrammetry for a number of applications involving above ground infrastructure, for example to reduce safety issues and costs when conducting a high accuracy inventory of above ground infrastructure. Until recently modern reality capture techniques have not been applied to underground infrastructure. But in the last few years this has begun to change. Since 2018 Lux Modus has applied LiDAR together with an accurate georeferencing device to achieve survey-grade location accuracy in "near real-time" as pipelines are constructed. As another example 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. Together with GNSS + RTK base station or previously surveyed control points.
Commercial cloud service
In France a new GéoCassini cloud service is available from e-cassini that commercially captures accurately georeferenced point clouds of underground utilities and allows this data to be integrated with other geo data such as orthophotos, traditional GIS maps, panoramic imagery, above ground imagery from LiDAR and photogrammetry, satellite and aerial imagery, and associated metadata. I had the opportunity to speak with Patrick Maïore, founder and director of e-Cassini.
GeoCassini is a cloud-based marketplace for various types of geospatial data including underrground utilities. The data is owned by the utility which captured it and is made commercially available to transportation agencies, construction contractors, other utilities via the GéoCassini cloud services. For example, standard part of the planning exercise for an engineering design firm would be to consult GéoCassini to see what underground and other data is available for the intended construction site.
Furthermore GéoCassini data can be integrated and visualized in augmented reality using vGIS. e-Cassini has a technology partnership with vGIS. For example, vGIS has been used to visualize underground networks and property boundaries stored in GéoCassini for a new housing development.
Applications
One of the most recent applications of GéoCassini is capturing LiDAR scans of open trench utilities. These could be newly installed utilities or utilities exposed during repair or relocation work. For example, GéoCassini has been used to capture using a handheld and share location information about above and below ground data for a 200 km water network for a water utility operating in several regions of France (Herblay, Mery-sur-Oise, Saint Leu, Nanterre, Vaucresson, and Suresnes.) The video capture was performed with a handheld app that was originally developed for Android and will soon be available for iOS. The data includes point clouds captured by mobile LiDAR and utility GIS maps of underground utilities.
The process used for reality capture is simple; the field operator walks along the trench and captures a video of the trench and the video is uploaded to GéoCassini where it is transformed into a point cloud. A few minutes later an analyst in the office receives a notification that the point cloud is available. The analyst georeferences the point cloud using control points captured in parallel with the video or from preregistered control points. Accurate GNSS+RTK points can be captured at the same time as the video is recorded. Alternatively, accurate control point scan be included in the field of vision of the video. Some public works companies carry out a preliminary survey of the site using LiDAR to develop a cloud of control point clouds. Another alternative is a service offered by GéoCassini to subscribers are control point clouds in the municipalities where they regularly work. The geo-referenced point clouds are saved in the GeoCassini database and all projects that have been linked to the point clouds are automatically updated. The information is shared amongl all stakeholders on each project.
The point clouds are used in many applications; drawing a proofing plan of the construction site, visualizing underground networks in 3D using augmented reality, and correcting and updating 2D data in the utility GIS are typical. But a big benefit is that they provide survey-grade location for underground infrastructure which enables precision engineering design with respect to the underground and the above ground.
e-Cassini has participated in two pilots in which the GéoCassini approach has been applied. In the first pilo,t which involved replacing aging house connections to the water network, after the new equipment was installed and before the trench was filled, a field technician captured a video of the newly installed equipment. The video was uploaded to GéoCassini where it was transformed into a point cloud and accurately georeferenced. The resulting georeferenced point cloud provides a high accuracy 3D image of the newly installed equipment available to all stakeholders of the project and potentially commercially available to other interested parties via the e-Cassini MarketPlace. The second pilot involved installation of an entirely new water network for a new development. The network was installed in sections. After each section installed and prior to filling the trench before re-filling the trench, a video was recorded, uploaded to GeoCassini, converted to a point cloud and geoferenced.
e-Cassini's technology has been implemented by Veolia, a large multinational water company, and by Bouygues, a large construction company. Veolia has conducted pilots using the technology in three regions of France, Normandy, Marseilles, and the Loire. Veolia has applied for and is expecting regulatory approval from the local D.S.P.s, which are equivalent to public utility commissions in North America.
Bouygues Energie et Service is currently experimenting with a GéoCassini solution for the renewal of public lighting network equipment in the municipality of Pornichet. GéoCassini is being applied to improve diagnostics of existing equipment and to optimize the location and type of new equipment.
Conclusion
A benefit of the GéoCassini cloud service is that it enables the capture and sharing of survey-grade as-built records of underground infrastructure. For new infrastructure this provides a reliable record of what was installed in the ground, in other words, survey-grade "as-constructed" instead of "as-designed". For existing infrastructure this enables discrepancies and omissions to be reported back to asset owners.
Another important benefit of the GéoCassini service is that it if very efficient and does not add to construction costs. Compared to the time required to call a surveyor to the site, video recording requires negligible time. Furthermore, the video approach does not interrupt construction work or affect scheduling and it works in most weather conditions, even at night in artificial lighting.
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