We describe ncWMS, an implementation of the Open Geospatial Consortium’s Web Map Service
(WMS) specification for multidimensional gridded environmental data. ncWMS can read data in a
large number of common scientific data formats – notably the NetCDF format with the Climate and
Forecast conventions – then efficiently generate map imagery in thousands of different coordinate
reference systems. It is designed to require minimal configuration from the system administrator
and, when used in conjunction with a suitable client tool, provides end users with an interactive
means for visualizing data without the need to download large files or interpret complex metadata.
It is also used as a “bridging” tool providing interoperability between the environmental science
community and users of geographic information systems. ncWMS implements a number of
extensions to the WMS standard in order to fulfil some common scientific requirements, including
the ability to generate plots representing timeseries and vertical sections. We discuss these
extensions and their impact upon present and future interoperability. We discuss the conceptual
mapping between the WMS data model and the data models used by gridded data formats,
highlighting areas in which the mapping is incomplete or ambiguous. We discuss the architecture of
the system and particular technical innovations of note, including the algorithms used for fast data
reading and image generation. ncWMS has been widely adopted within the environmental data
community and we discuss some of the ways in which the software is integrated within data
infrastructures and portals