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Definition and Introduction

Coverage metadata is metadata which is known to be a characteristic of a given data source. It contains elements which are vital to the correct georegistration of data. It also contains elements which are implicit to the particular data format, so long as the data format is specific to a particular data source (e.g., the MODIS instrument or the Weather Research and Forecasting model) or explicitly specified by a more general data format. Coverage metadata includes:

  • Number of pixels in each dimension.
  • Information about the Coordinate Reference System (CRS).
  • Information about how the pixels are aligned to the grid (pixel center, upper left, lower right, etc.)
  • Information about the spectral bandpass of each band.
  • Units
  • Coordinate axes names
  • Number of datasets in the file
  • Name of each dataset

Coverage metadata excludes anything which is not available from the data format in which the coverage is stored. If you are looking for a general purpose metadata mechanism, this page is not for you.

ISO19115

ISO19115 is a metadata format specified by ISO. It is the currently the favored alternative in the search for a common language which can be spoken by both coverage I/O plugin and coverage framework. These attachments and pages explore how it might be used to facilitate communication between plugin and client code.

Resources

  • ISO19115 Specification is a link to a draft version of the 19115 specification. This version should be substantially similar to the version which was accepted by the ISO and which is currently for sale as an international standard.
  • Dataset Axes Description is an early attempt to explain the importance of permitting access to gridded data by grid index instead of real world coordinates. It also contains a summary of the manner in which certain self-describing formats (e.g., HDF and netCDF) represent axes. As such, the chosen metadata system should be able to accomodate these schemes.
  • J2SE IIOMetadata is an experiment by Simone on how to integrate metadata with J2SE ImageIO as IIOMetadata. This illustrates some of the limitations and capabilities of the IIOMetadata construct, including the importance of the distinction between stream and image metadata. ISO19115 could be used as the IIOMetadata objects which are returned from the coverage.
  • ISO19115 Usage.pdf is a collection of notes on how this standard would be used inside a Coverage I/O framework. It also shows what an ISO19115 profile containing the minimum mandatory elements actually contains.
  • StreamAndImage.pdf is a description of how we can map the notion of a metadata heirarchy as described by the standard into a separation of stream metadata and image metadata.
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