GSIP 158

GSIP 158 - NetCDF output support for variable attributes and extra variables

Overview

Proposed By

Ben Caradoc-Davies

Assigned to Release

This proposal is for GeoServer 2.12-beta.

State

• Under Discussion
• In Progress
• Completed
• Rejected
• Deferred

Motivation

NetCDF/GRIB sources contain rich metadata in the form of variable attributes and extra variables that give meaning to data. When a coverage is read from a NetCDF/GRIB source, this information is lost, even if the output from GeoServer is NetCDF that is capable of representing this information.

Proposal

Functionality

The new NetCDF output functionality is intended to work with both single-file NetCDF/GRIB sources and also ImageMosaics of NetCDF/GRIB files.

For NetCDF output add:

1. An option to allow all attributes to be copied from the source NetCDF/GRIB variable to the target variable.
2. Support for manual configuration of variable attributes, much like the current support for setting global attributes.
3. Support for configuration of extra variables which are copied from the NetCDF/GRIB source to the output; initially only scalar variables will be supported. Extra variables can be expanded over "higher" dimensions, that is, values copied from one scalar per ImageMosaic granule are assembled into a multidimensional variable over, for example, time and elevation.

User interface changes

Current interface:

Proposed interface:

Implementation

The proposed approach is to pass a NetCDF/GRIB source URL from GeoTools to GeoServer gs-netcdf-out in a coverage property and have NetCDFOutputManager do all the work.

Proposed changes:

• Addition of a coverage property SourceUrl for NetCDF and ImageMosaic readers that can be discovered by NetCDFOutputManager in GeoServer gs-netcdf-out. The property is a URL for the source of the coverage.
• Implementation of the user interface and settings serialisation in GeoServer gs-netcdf-out
• Implementation of the new variable attribute and extra variable functionality in NetCDFOutputManager in GeoServer gs-netcdf-out

Backwards Compatibility

The proposed implementation is designed to preserve existing functionality and behaviour. Configuration files that lack the new settings will continue to work as before.

Feedback

Voting

Project Steering Committee:

• Alessio Fabiani:
• Andrea Aime:
• Ben Caradoc-Davies:
• Brad Hards:
• Christian Mueller:
• Ian Turton:
• Jody Garnett:
• Jukka Rahkonen:
• Kevin Smith:
• Simone Giannecchini:

Links

• Discussion on geoserver-devel mailing list
• Draft implementation: [GEOT-5709] Support coverage property SourceUrl
• Draft implementation: [GEOS-8099] GSIP 158 - NetCDF output support for variable attributes and extra variables
• Jira: [GEOT-5709] Support coverage property SourceUrl
• Jira: [GEOS-8099] GSIP 158 - NetCDF output support for variable attributes and extra variables