Down to the nearest centimetre…

Do you know who was responsible for determining the exact position of the lines reproducing those of the accelerators that were traced on the floor of the Main Building for the fiftieth anniversary celebrations of the PS? Do you know who is checking that Building 40 doesn’t budge an inch during the construction of Building 42? And who would you ask if you wanted to know the exact position of the water pipes in Building x or y? Youri Robert and the team from the Patrimony and Site Information Service (GES-SEM-DOP), of course!


Youri Robert at work

The CERN site and its buildings are permanently evolving, just like the people who work there. When you've got a total of 15,000 different premises (see box), you're bound to have a wall being knocked down here and another going up somewhere else most days. Everything has to be measured, inventoried, put on computer, archived and made available on the Web. And the Laboratory's buildings on the surface are only half the story: let's not forget the underground infrastructures, the tunnels and the plots of land, not to mention the kilometres of optical fibres and electric cables passing through them.

Youri Robert and his team are there to make sure that all this information is always up to date. "Each Department at CERN has a "space manager" responsible for informing us of any change to the premises using the form available on our Web site. We update the drawings accordingly and, where applicable, add the corresponding attribute data to our database, such as the construction type for entire buildings or the purpose for which a room is going to be used in the case of individual premises".

When a change is made to premises, a building or a plot of land, the first task of Youri and his team is to measure the area concerned. "We use a distance metre for this indoors and a tachymeter outdoors. These are very precise devices that allow us to measure angles and distances", he explains. "The angles and distances we measure are converted into coordinates. We then enter them in a special CAD software tool so that they can all be digitised."

CERN's surveyors have the very latest state-of-the-art tools at their disposal. "We have just acquired a GPS system that allows us to take measurements to the nearest centimetre, a precision 100 times greater than that of a standard GPS system", Youri enthuses.


Did you know?

The CERN site consists of 213 hectares of fenced land, and over 600 hectares of land are placed at the Organization's disposal by the Host States. The site contains around 600 buildings representing a total of more than 15000 different premises.

All the digitised drawings can be accessed from the Patrimony and Site Information Service Website. "The Website contains two applications", Youri explains. "The NS application gives us a dynamic representation of all CERN's graphic data and networks, while the "Planothèque" application contains the floor plans of all CERN's buildings".


Youri Robert's career to date

Youri graduated with a degree in surveying from the Ecole Supérieure des Géomètres et Topographes (ESGT) in France. Towards the end of his studies in 1996, he worked as a Fellow in CERN's "Survey" Group, which is responsible for metrology and, in particular, the alignment of the LHC magnets and detector components. He then spent two years working for the land registry office of Mayotte, an island in the Indian Ocean, and the three years after that working for a large surveying firm in Grenoble. After that he returned to CERN for three years, where he worked on the measurements for the LHC magnets and for the ATLAS experiment before being hired by the Geographical Information System of the Commune of Nyon in nearby Switzerland. He has been head of CERN's Patrimony and Site Information Service since 2008.

Previous Bulletin articles on CERN's surveyors:

Youri concludes: "Our work is extremely diverse. We can be working in the field one day, doing computer-aided design another and web production the next. This is really important for me. And in an international environment with experts from all over Europe into the bargain. We don't face the same constraints as you sometimes find in the private sector as we are given the tools and the time we need to do our job properly.

The medium to long-term priority for Youri's team will be to produce a 3D version of the drawings of the Laboratory's different sites. The Canton of Geneva is already in the process of doing this for all its sites and buildings.



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by CERN Bulletin