Ferret properties in the dataset XML configuration are sent to the Ferret backend and used by the scripts there to set some details about datsets or the visualization style to use. AddXML inserts some properties automatically. They can be further customized by the installer.
For instance one could add this to use contour lines by default when drawing for 2-D plots of the Salinity variable in the Levitus Climatology dataset.
... <variables> <salt name="SALINITY" units="PPT"> <link match="/lasdata/grids/levitus_climatology_cdf_grid"/> <properties> <ferret> <fill_type>contour</fill_type> </ferret> </properties> </salt> ...
There are a few properties that are not related to graphics:
|init_script||name of init script||Applies to a dataset. See the documentation
on init scripts.
|init_commands||any Ferret commands to be executed upon starting||Commands to be executed upon starting: if more
than one command, separate them with a ;
|start_memory||initial memory to assign to the Ferret process||Blocks of memory in Mwords. Ferret starts with
24 Mwords by default.
|add_a_note||Text to add as a NOTE in the annotations box||If the text contains the letters url then url will be replaced by the url given in the property url_for_note. The text coming after url will be made into the live link in the box. See the examples below.|
|url_for_note||A relative url or full working url||The link to use for the NOTE annotation given by the add_a_note property. See the examples below.|
For example, to add a note to the annotations box saying These data are updated daily, add a property to the dataset XML file:
<properties> <ferret> <add_a_note>These data are updated daily</add_a_note> </ferret> </properties>
Or, to put in a link to a document related to the data, the url_for_note tag is added. It might contain a full url, or if the document data_2014.html has been added to the WebContent/docs/ directory, it is a relative url to the docs/ directory for this LAS installation. The following would add a note with the text in parentheses as the link to the document:
Please see (these additional notes)
<properties> <ferret> <add_a_note>Please see url these additional notes</add_a_note> <url_for_note>docs/data_2014.html</url_for_note> </ferret> </properties>
From the User Interface the Plot Options dialog allows the user to send Ferret properties to Ferret. Most of these can also be set in the configuration for a dataset or variable.
These properties apply to graphics in general:
Here are some properties particular to 2Dcolor plots:
|palette||name of a color
|This must be the name of the palette file (not all names in menu listed
in the LAS UI are file names).
|Style for 2D single-variable plots:
color-filled with contour lines
|fill_levels||a levels specifier||The default is variance-based levels determined from the data. A common
specifier is c for centered levels. See the help in the Plot Options under
"Color Fill Levels".
|mark_grid||none, all, subsample||Controls whether tiny dots are drawn at all grid-cell locations, or a
subset of the locations.
Here are the properties that addXML inserts when it detects a variable that is best viewed on a centered color palette, and with centered levels, such as wind components:
These properties will apply to line plots:
|line_or_sym||line, sym, or both||Sets the line style: line, symbol at coordinate locations,
or both line and symbols.
|line_color||black,red,blue,green,lightblue,purple||Line color; black is the default.|
|line_thickness||l1, 2, or 3||Sets the line thickness 1=thin, 2=medium, 3=thick|
|Sets the limits and optionally the delta-value on the dependent axis.|
At this time Ferret properties cannot be applied to Vector plots.
These are the settings that addXML makes when it detects variables on a curvilinear grid. The names of the curvilinear coordinate variables are specific to the grid, and the lon_min and lon_max values are computed from the grid.
<properties> <ferret> <curv_lon_min>-101.74989476701279</curv_lon_min> <curvi_coord_lat>lat_rho</curvi_coord_lat> <curvi_coord_lon>lon_rho</curvi_coord_lon> <curv_lon_max>-53.25308436246699</curv_lon_max> </ferret> </properties>
As is described in the section on Configuring Data on Curvilinear Grids, other properties may be added to describe operations to regrid the data, and to specify portions of the grid that are rectilinear to improve performance.
Here is the list of all properties that have to do with curvilinear grids:
|curvi_coord_lon||name of coordinate variable||Curvilinear coordinate variable
|curvi_coord_lat||name of coordinate variable||Curvilinear coordinate variable
|curv_lon_min||minimum value||Pre-computed from curvi_coord_lon.|
|curv_lon_max||maximum value||Pre-computed from curvi_coord_lon.|
|curv_lat_min||minimum value||Pre-computed from curvi_coord_lat
(optional, improves performance).
|curv_lat_max||maximum value||Pre-computed from curvi_coord_lat
(optional, improves performance).
|lon_modulo||0 or 1||If set, longitude coordinate is to be treated as modulo.|
|curvi_coord_mapfile||pre-computed map file||File name including its path containing the mapping
for regridding to rectilinear grids.
|curvi_coord_mapvar||mapping variable||Name of the mapping variable in
the map file.
|traj_discrete||1 or 0||Set to 1 to apply a test for data on a trajectory.
If the sampling along the track is discrete rather than
continuous, the plot will have individual blobs of color
connected by a thin black line