The ocean network within ICOS consist of a variety of ships and fixed station installations covering the open ocean and coastal areas, and for this purpose the network is divided into 3 categories; Ships of Opportunity (SOOP; previously known as VOS), Fixed Ocean Stations (FOS), and Marine Flux Towers (MFT). For each category, the required variables (called core variables) and the frequency of measurements are defined in the tables in the ICOS Ocean Labelling Step 2 document. The tables also defines the criteria to become a Class 1 and Class 2 station. This classification is a part of the ICOS station labelling process.
OTC aim at including the additional category Repeat Ocean Sections (ROS) into the network.