The northern part was much the longer since it had been accurately measured by Cassini de Thury in 1740. Delambre was given charge of the Dunkerque to Rodez sector and Méchain the Rodez to Barcelona sector much of which had not been previously surveyed.
Ang hilagang bahagi ay marami ang na dahil ito ay nai-tumpak na sinusukat sa pamamagitan ng Cassini de Thury sa 1740. Delambre ay binibigyan ng singil ng Dunkerque sa Rodez sektor at Méchain ang Rodez sa Barcelona sektor ng marami na may hindi pa dati ipasukat.