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 filemapper
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