Trezien lighthouse is located on mainland, 1,5 kilometers from Corsen Cape  which separates Atlantic Ocean from Manche Sea.
Opened in january 1894 , it is equipped with a directional light, aligned with Kermorvan lighthouse.
It allows a safe in and out traffic on  Four channel.
Nearby Cross Corsen Center can be found, dedicated to traffic surveillance  and rescue coordination  on  Manche west sector.