Radiocarbon when used for dating purposes requires calibration against known-age material. Such material is normally dated using other methods such as dendrochronology (for wood) or Uranium series methods for corals and speleothems. Work on archives of material suitable for calibration purposes is carried out by researchers in institutions from around the world.
The IntCal working group's aim is to summarise this information in a statistically robust way so that it can be used for calibrating radicoarbon dates from different environments. This enterprise has a long history with the first comprenesive curve generated in 1986.