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Spherical plot window
The spherical plot window draws 3-dimensional scatter plots
of datasets from one or more tables on spherical polar axes,
so it's suitable for displaying the position of coordinates on
the sky or some other spherical coordinate system, such as the
surface of a planet or the sun.
You can display it using the Sphere (
) button
in the Control Window's toolbar.
In most respects this window works like the
3D Plot window,
but it uses spherical polar axes rather than Cartesian ones,
You have to fill in the
dataset selector
at the bottom with longitude- and latitude-type coordinates
from the table.
Selectors are included to indicate the units of those coordinates.
If TOPCAT can locate columns in the table which appear to represent
Right Ascension and Declination, these will be filled in automatically.
If only these two are filled in, then the points will be plotted on
the surface of the unit sphere - this is suitable if you just want to
inspect the positions of a set of objects in the sky.
You can optionally fill in the Radius selector as well.
If you do this, then points will be plotted in the interior of the
sphere, at a distance from the centre given by the value of the radial
coordinate.
The following buttons are available on the toolbar:
-
Split Window
- Allows the dataset selector to be resized by dragging a separator
between it and the plot area. Good for small screens.
-
Replot
- Redraws the current plot. It is usually not necessary to
use this button, since if you change any of the plot characteristics
with the controls in this window the plot will be redrawn
automatically. However if you have changed the data, e.g. by
editing cells in the Data Window,
the plot is not automatically redrawn (since this is potentially an
expensive operation and you may not require it).
Clicking this button redraws the plot taking account of any changes
to the table data.
-
Configure Axes
- Pops up a dialogue to allow manual configuration of axis ranges
and labels - see Appendix A.4.1.2. The only configurable
axis range is the upper limit of the radial axis.
-
Export as EPS
- Pops up a dialogue which will write the current plot as an EPS file.
In general this is a faithful and high quality rendering of what
is displayed in the plot window. However, if plotting is being done
using the transparent markers, it won't come out right since
transparency cannot be represented in PostScript; the markers will
be rendered as if they were opaque.
Currently, if there are many points being plotted, this can result
in a rather large output file.
-
Export as GIF
- Pops up a dialogue which will output the current plot to a GIF file.
The output file is just the same as the plotted image that you see.
Resize the plotting window before the export to control the size
of the output GIF.
-
Rescale
- Rescales the axes of the current plot so that it contains all
the data points in the currently selected subsets.
By default the plot will be scaled like this, but it it may have changed
because of changes in the subset selection.
-
Reorient
- Reorients the axes of the current plot to their default position.
This can be useful if you've lost track of where you've rotated
the plot to with the mouse. This also resets the zoom level to
normal if you've changed it.
-
Stay Upright
- Toggle button which when selected ensures that the north pole
(latitude = +90 degrees) is oriented vertically on the screen at all times.
By default this is on.
-
Grid
- Toggles whether the spherical wire frame bounding the plot
is drawn or not.
-
Draw Subset Region
- Allows you to draw a region on the screen defining a new
Row Subset. When you have finished
drawing it, click this button again to indicate you're done.
The subset will include points at all depths in the viewing direction
which fall in the region you have drawn.
See Appendix A.4.1.5 for more details.
-
Subset From Visible
- Defines a new Row Subset
consisting of only the points which
are currently visible on the plotting surface.
See Appendix A.4.1.5 for more explanation.
The following additional item is available as a menu item only:
-
Antialias
- Toggles whether the axes and their annotations are drawn antialiased.
Antialiased lines are smoother and generally look more pleasing,
especially for text at a sharp angle, but it can slow the rendering
down a bit.
The Dataset Toolbar contains the following options:
-
/
Add/Remove dataset
- See Appendix A.4.1.1.
-
/
Add/Remove auxiliary axis
- See Appendix A.4.1.4.
-
Toggle tangential error bars
- When activated, an additional column selector appears in the
dataset panel to the right of the Longitude and Latitude selectors,
along with its own unit selector. You can fill this in with an
isotropic error value representing the radius of a small circle
associated with the selected points, in units of arcsec, arcmin,
degrees or radians. This will cause 2-d error bars to be plotted.
You can configure their appearance (e.g. crosshairs, ellipses,
rectangles, ...) using the
style editor in the usual way.
See Appendix A.4.1.3 for more information.
-
Toggle radial error bars
- Switches radial error bars on and off. See Appendix A.4.1.3.
You have considerable freedom to configure how points are plotted
including the shape, colour and transparency of symbols and the representation
of errors if used. This works exactly as for the
Cartesian 3D plot as described in
Appendix A.4.5.1.
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Next: Density Map
Up: Graphics Windows
Previous: 3D Plot Style Editor
TOPCAT - Tool for OPerations on Catalogues And Tables
Starlink User Note253
TOPCAT web page:
http://www.starlink.ac.uk/topcat/
Author email:
m.b.taylor@bristol.ac.uk