How to measure 42.195 metres for a marathon

On the eve of the 2008 marathon of Rotterdam one of the Dutch new papers published an article on the technique used to measure the route of the marathon  (article in article in PDF).

What we learn from this article is:

1. A marathon is usually longer than 42.195 kilometre. 
2. It is measured with old fashioned low tech

Why is a marathon longer? In case the winner runs a world record the track is measured a second time. To avoid that the track is not long enough one meter is added on every kilometre!

On top of this; most runners will not run the ideal line. The elite runners as well run probably a couple of 100 metres extra.

The low tech devise used to measure the distance is a very simple but effective devise called the Jones-counter. This is connected to the wheel of a bicycle.