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#### A.4.4.7 Area Layer Control

The Area layer control () allows you to plot a two-dimensional shape from each row of a table. This might typically be something like an instrument coverage footprint corresponding to an observation. The shape may be specified in various different ways: as an STC-S region specification string (as found for instance in the `s_region` column of ObsCore or EPN-TAP query results), as an array specification of polygons or circles, or as an ASCII-encoded MOC. You can add one of these controls to the stack by using the Add Area Control () button in the control panel toolbar or the corresponding item in the Layers menu for suitable plot types (Plane, Sky or Sphere).

Areas specified in this way are generally intended for displaying relatively small shapes such as instrument footprints. Larger areas may also be specified, but there may be issues with use, for instance auto-determination of the initial plot region may not work so well, and the rendering of shapes that are large relative to the sky may be inaccurate. These issues may be addressed in future releases.

Sky Plot Window with an Area control

This control is a Table Data control as described in Appendix A.4.2.2. That section explains the Subsets tab; the Position and Form tabs are described in more detail below.

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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
Mailing list: topcat-user@jiscmail.ac.uk