The MERIS instrument delivers a unique dataset of ocean colour measurements of the coastal zone, at 300m resolution
and with a unique spectral band set. The motivation for the Coastcolour project is to fully exploit the potential of the
MERIS instrument for remote sensing of the coastal zone. The general objective of the project is to develop,
demonstrate, validate and intercompare different processing algorithms for MERIS over a global range of coastal water
types in order to identify best practices. In this paper the Coastcolour project is presented in general and the Regional
Algorithm Round Robin (RARR) exercise is described in detail. The RARR has the objective of determining the best
approach to retrieval of chlorophyll a and other marine products (e.g. Inherent Optical Properties) for each of the
Coastcolour coastal water test sites. Benchmark datasets of reflectances at MERIS bands will be distributed to algorithm
provider participants for testing of both global (Coastcolour and other) algorithms and site-specific local algorithms.
Results from all algorithms will be analysed and compared according to a uniform methodology. Participation of
algorithm providers from outside the Coastcolour consortium is encouraged.