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3.1 Simplified Region Specification

Any region string representing the union of basic shapes should consist of the word REGION followed by a number of shape descriptions, see table below. Here you can find the proper BNF of the language.

Example

Here is the simple example of overlapping circles:
   REGION
     CIRCLE J2000 180 0 1
     CIRCLE J2000 181 0 1

Table of shapes

Convex

CONVEX J2000 {ra dec D}*
CONVEX CARTESIAN {x y z D}*
CONVEX {x y z D}*

Rectangle

RECT J2000 {ra dec}2
RECT CARTESIAN {x y z }2

Circle

CIRCLE J2000 ra dec R
CIRCLE CARTESIAN x y z R

Hull

CHULL J2000 {ra dec}3+
CHULL CARTESIAN {x y z}3+

Notation

{...}*   0 or more instances of the syntax element between the braces
{...}2   exactly 2 instances of the syntax element between the braces
{...}3+  3 or more instances of the syntax element between the braces

R        is degrees in arcminutes.
D        is a real number between -1 and 1


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