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This icon can directly visualise ODB data in using various plot types. Optionally it can perform an ODB/SQL query on the input ODB and visualises the resulting (intermediate) data. It works for both databases (ODB-1) and files (ODB-2).
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From Macro/Python the icon can be called as odb_visualiser(). |
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A tutorial about using ODB in Metview can be found here. |
What is ODB?ODB is a database developed at ECMWF to store and retrieve large volumes of meteorological observational and feedback data efficiently for use within the IFS. Currently, ODB comes in two flavours: - ODB-1 (the original hierarchical table format capable of running in a parallel environment within IFS)
- ODB-2 (a new flat format with a modern API used for archiving in MARS).
How does ODB/SQL query work in the ODB Visualiser?We illustrate it with a simple example. Let us suppose we want to perform this ODB/SQL query on our data then want to plot the results as points on a map: | Code Block |
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| SELECT
lat@hdr,
lon@hdr,
fg_depar@body
WHERE
vertco_reference_1@body = 5
ORDERBY
obsvalue@body |
Then in the icon editor we need to set the following parameters: | ODB Latitude Variable | lat@hdr | | ODB Longitude variable | lon@hdr | | ODB Value Variable | fg_depar@body | | ODB Where | vertco_reference_1@body = 5 | | ODB Orderby | obsvalue@body |
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The ODB Visualiser Editor
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Specifies the maximum number of rows in the result. If -1 is given here the number of rows is not limited in the output. The default value is -1.
ODB
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Coordinates Unit
Specifies the units of the geographical co-ordinates in the input ODB. The possible values are: degrees and radians. The default is degrees.
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For older ODBs if column latlon_rad@desc tells us the geographical co-ordinate units. Its 0 value indicates degrees while 1 means radians. Newer ODBs, especially the ones retrieved from MARS, as a generic rule, always use degrees as geographical co-ordinate units. |
ODB Binning
Specifies the Binning used to grid create gridded data out of scattered data when the ODB Plot Type is xy_binning.
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