In early 2018, LevelS3D was selected by the RATP Group to enter its « Tech for Infrastructure Design » challenge at VivaTech Paris. Hence, we had the opportunity to meet various people with this public transportation actor, with whom we discussed many use cases (BIM, maintenance, engineering, customer experience, etc.) based on 3D scanning. We made a demonstration of our new high-end 3D scan service offer, coupled with our S3D Capture mobile app to update and maintain 3D models. We finished second in this challenge and we were able to leave with valuable exchanges allowing us to envisage future collaborations between the RATP and LevelS3D. (Photo: Yannick Folliard at the VivaTech Paris show)

An unusual scanning project

A few weeks after VivaTech, we were contacted by the RATP Group for a first digitization project of a Paris metro station with a particular objective: make a photo inventory of the station to identify all the water seepage in the Republique metro station. The goal was to map the entire station and have maintenance people identified the seepage, from any location, through high-definition 360° pictures, and assess its status.

Preparation is king

Republique Station, with its 130,000 sq ft, is one of the largest stations of the RATP network, serving five lines (3, 5, 8, 9, 11), with a tangle of corridors worthy of the largest labyrinths. As the inventory needed to be exhaustive, the biggest challenge was the need to scan every wall and ceiling, and not forget any part of the station. So we had to think about creating routes to follow that would allow us to logically and optimally cover the entire surface. The other constraint was the timing: scanning had to be made at night as the station was locked, ie only four hours a night, from one to five in the morning. We finally agreed on scanning for two nights, taking a bit of margin on the opening and closing hours.

Without a thorough knowledge of the station, we could not create the routes ourselves. The RATP teams provided us with valuable information: 2D maps of the station, as well as the routes to be followed to ensure scanning completion and to optimize travel time.

Finally, we carried out an on-site tracking to identify the routes and the potential difficulties that we could encounter. We plunged into the backstage of a metro station, starting with the joint inspection visit prior to our intervention, which helped us a lot to understand access issues. Indeed, beyond an unusual architecture, a metro station has mainly security and access constraints that must be respected: one-way escalators that do not work at night, gantries to manage entrances and exits of users, or areas to avoid such as docksides.

A challenging digitization

We arrived there a little after 10pm. We were able to store our equipment in a restroom located behind the counter where the various RATP staff were intrigued to see us assemble our equipment. As a matter of fact, we use a scanning trolley equipped with 3D sensors and HD 360° cameras. This allows us to capture the geometry of the building, but also to take pictures of the scene every 2 meters. The big advantage of the technology is the speed of data acquisition where, unlike most static scanners, the data is acquired continuously without the need to multiply the stations, allowing to scan much faster. It measures a little less than 2 meters (unfolded) and weighs more than 40 kg. The escalators were out of service at night, so the main problem we had to deal with was crossing the stairs in which we had to carry the cart. And stairs in the Republique metro station, there are many!
Some control lines that do not have service gates have also prevented us from accessing certain exits that we had to scan through the outside accesses of the station. This compelled is to cross the huge Place de la Republique in the middle of the night with the trolley. In such cases, the use of the S3D Capture mobile scan application proves to be very complementary to cover difficult to access areas in order to save time and avoid dangerous maneuvers.