naiad-tile command in detailsΒΆ

The naiad-tile commandline tool allows to extract the metadata from a granule file at global level (properties or attributes valid for the whole file content) and at a finer division level (subsets of the granule refered to as tiles).

These properties are later registered into an index (implemented by ElasticSearch). These properties include:

  • time frame of the data
  • spatial boundaries (shape) of the observed area
  • any custom property that one may want to extract from the data, as a future search/selection criterium.

The most basic behaviour is to call naiad-tile with the two mandatory arguments:

naiad-tile <file> <mapper>

where:

  • file is the full path to the granule file
  • mapper is the name of the mapper class in cerbere package to read this type of granule.

for instance:

naiad-tile 20100123-EUR-L2P_GHRSST-SSTsubskin-AVHRR_METOP_A-eumetsat_sstmgr_metop02_20100123_000103-v01.7-fv01.0.nc GHRSSTNCFile

This will result in a single tile matching the full area covered by the granule. You see that by using the --show option:

naiad-tile --show 20100123-EUR-L2P_GHRSST-SSTsubskin-AVHRR_METOP_A-eumetsat_sstmgr_metop02_20100123_000103-v01.7-fv01.0.nc GHRSSTNCFile

This is not exactly what we want, because tiles are meant for fine spatial and temporal subsetting. A good compromise is usually to have a tile size of about 500km along and accross track. This can be set by using the --xstep and --ystep (along-track) options where the value is given in pixels. Adjust this value so that the tile size is about 500km.

naiad-tile --show --xstep=540 --ystep=540 20100123-EUR-L2P_GHRSST-SSTsubskin-AVHRR_METOP_A-eumetsat_sstmgr_metop02_20100123_000103-v01.7-fv01.0.nc GHRSSTNCFile