The 24 hour speed record explained

The leading sailors on the race have been recording some high average speeds and covered many miles at high speeds since they hooked into the front of the low pressure system. But while there has been an expectation the 24 hour record would fall, so far it remains intact. 

The solo mark in question is that of Alex Thomson who sailed 536.81 miles in 24 hours during the Vendée Globe on 16th January 2017.  So far some of the leaders of the Retour à La Base have recorded greater distances “on the water” (that is actual distance travelled), but the record is measured on the Great Circle (theoretical route), between point A and point B. 

The great circle or orthodromic distance is the shortest distance between two points on the surface of a sphere, measured along the surface of the sphere.