TWiki> IVOA Web>IvoaDataModel>STC>STC-1_33-Errata>STC-1_33-Erratum-2 (2018-12-20, LaurentMichel) EditAttach

Author: DM WG

Date last changed: 2018-11-18

Date accepted:

This erratum is to correct an error reported at the IVOA interop in Victoria, BC: May 2018

*Section 4.5.1.4 (pg 30-31: Region.Polygon) states:**"The inside of the region is defined as that part of coordinate space that is encircled by the polygon in a counter-clockwise sense. What this means is that, in a plane, if A > 0, the “inside” of the polygon is included; if A < 0, the “outside” is selected. On a sphere with a left-handed (celestial) coordinate system, if A > 0, one has identified the inside of the polygon; if A < 0, one used the “outside” angles of the polygon and the area is really 4π − A *

This is also wrong because if A < 0 then 4*pi – A is > 4*pi, and that cannot be.

The correct text is:

- Section 4.5.1.4 (pg 30-31: Region.Polygon) :
**if A < 0, one used the “outside” angles of the polygon and the area****is really 4π − A**.

- Software using the wrong formula must be updated

Topic revision: r3 - 2018-12-20 - LaurentMichel

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