The EDAL project comprises a set of libraries to deal with the manipulation and visualisation of environmental data. They were originally created as part of ncWMS but are standalone libraries which ncWMS uses.
EDAL consists of a number of modules, each focused on a different task. These modules are outlined below
The edal-common module contains the core data model used in EDAL, as well as in-memory implementations of this data model, common utility methods, and exceptions.
The edal-graphics module contains code for generating images from the core EDAL data types. This includes map images, as well as timeseries, vertical profile, and vertical section charts. Additionally there are custom SLD (Styled Layer Descriptor) handlers to allow for the precise specification of how to assemble a map image, allowing arbitrarily complex plotting of multiple simultaneous data layers.
This module depends on the edal-common module.
The edal-cdm module uses the Unidata NetCDF-Java libraries to read data into the core EDAL data model. It reads CF-compliant gridded NetCDF files as well as OPeNDAP, GRIB, and several other formats (see http://www.unidata.ucar.edu/software/thredds/current/netcdf-java/reference/formats/FileTypes.html for a list). It also includes a data reader capable of reading the UK Met Office EN3/4 in-situ datasets (http://www.metoffice.gov.uk/hadobs/en3/ and http://www.metoffice.gov.uk/hadobs/en4/).
This modules depends on the edal-common module.
The edal-wms module contains an implementation of the WMS (Web Map Service) standard with a number of custom requests suited to exposing environmental data over the web. This module is not a complete packaged WMS - it supplies all of the required servlet classes, but requires a data catalogue to be implemented to map WMS layer names to the EDAL data objects.
This module depends on the edal-common module and the edal-graphics module
The edal-xml-catalogue module contains an implementation of a data catalogue in an XML format. This allows configuration of a set of datasets through XML for provision to the graphics module.
This module depends on the edal-common module and the edal-graphics module
The edal-godiva module is a Google Web Toolkit (GWT) based WMS client. It supports all of the extended WMS requests supplied by the edal-wms module.
This module does not depend on any others.
EDAL was developed primarily to factor out common functionality from the original ncWMS (http://sourceforge.net/projects/ncwms/)
Caching of datasets to improve performance is implemented using Ehcache. Two distinct caches are included in EDAL:
- A cache for datasets "featureCache"
- A cache for maps "meshDatasetCache"
When using ncWMS2 another cache is available:
- A cache for dynamic datasets "dynamicCache"
Configuration for the caches can be configured using ehcache.xml which can be specified at run-time with the JVM parameter '-Dehcache.config="/path/to/ehcache.xml"'. The default configuration is specified in /common/src/main/resources/ehcache.xml.
The Ehcache cache can be distributed using Terracotta by specifying the parameters in ehcache.xml. An example file is provided in /common/src/main/resources/ehcache.terracotta.xml.
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The EDAL libraries are developed by the Reading e-Science Centre and are maintained by @guygriffiths.
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