Check out this link, then read following commentary.
Hugh Jones writes:
Dear Ms Bogin,
David Katz copied me your message. I am the official measurer of the Berlin Marathon, and every year provide international validation of the work done by John Kunkeler and Siegfried Menzel in Berlin (copied). Berlin and London Marathons operate such a system of international validation in case of world records being set - as they can then be announced immediately (subject to dope testing results) without further re-measurement. The international validator for London for many years was Pete Riegel (USA) but from next year will be Dave Cundy (AUS) (both copied). A similar system of international validation exisits for international championships, such as London 2012, where I will do the measurement and David Katz will be the international validator.
Whatever aspersions Mr Kannouchi has cast upon the accuracy of the Berlin course have not arisen from any knowledge of how the measurement of road race races is conducted. Who are the "experts" that he mentions in his answer to you? They are not road race measurers. I am sure that the measurers of the Chicago Marathon would not make such unfounded accusations.
IAAF-AIMS International Measurement Adminstrator
Pete Riegel writes:
Dear Ms Bogin,
Allegations by athletes that certain courses may be short are regrettably not rare, but substantiation is. I'm sorry to see an athlete of Mr. Khannouchi's caliber fall into the trap. It does not do him credit, nor does publication of his unsubstantiated comments burnish your aura.
I have been measuring road races for 30 years, and verify that it's no longer the Bad Old Days of short courses. At one time marathon times were suspect, but those days are long gone. Checks and balances are in place, and have been for decades.
Berlin Marathon has long been measured to the highest standard, and times there may be taken as valid.
Sincerely, Pete Riegel