In athletics, some disciplines are difficult for spectators to follow. In the long jump, for example, it is not easy to judge whether the last jump has set a new record.

Virtual lines can help a TV audience to see what is happening, but they are not visible to spectators in the stadium. The PrimeLine system, developed by Golden Fly Sports GmbH, solves this problem by projecting the ‘mark to jump’ onto the sand.

The mobile installation was devised by Armin Margreiter, the former national coach of the Austrian long jump team, in conjunction with the laser projection specialist MediaLas.

It consists of three laser diodes, which are aimed at the pit and produce a visible line — even in direct sunlight.

The developers needed a drive unit that could move the lasers along distances ranging from three to 12m, but because long jumpers tend to kick up a lot of sand upon landing (and this can bind with the lubricants used in a conventional linear guide system, causing it to stick), the development team needed a system in which all the components were robust, resistant to sand and lightweight.

They selected linear bearings made of the lubrication-free high-performance polymer Iglidur J200 from Igus (www.igus.co.uk/drylin). Because the Drylin linear-guide bearing remains dry, sand does not adhere to it; moreover, its low coefficientof friction allows the precise positioning required by the IAAF.

Drylin is corrosion-resistant and maintenance-free; it also has a long service life, allowing it to be used continuously — even during long competitions.

Mr Margreiter said: “The linear guides from Igus have been in use on my systems for four years, and they have never posed the slightest problem.”