STC-1_33-Erratum-1 < IVOA

---+ STC-1.33 Erratum 1:

Author: DM WG

Date last changed: 2018-11-16

<span style="background-color: transparent;">Date accepted:</span>
---++ Rationale

This erratum is to correct an error reported at the IVOA interop in Victoria, BC: May 2018
---++ Erratum Content
<div title="Page 6">

The formula in 4.5.1.4 states:

<span style="background-color: transparent;">  &ldquo;A = - SUM[ A(i) ] &ndash; (n-2) *pi&ldquo;</span>

but:<br />  A = (RA,DEC)[0] = (90, 0)

  B = (RA,DEC)[1] = (0, 0)

  C = (RA,DEC)[2] = (0, 90)

The three angles of the polygon are all 90 deg, or pi/2 rad by construction.

A in the above case is: -3 * pi/2 &ndash;pi = -5/2 pi

One expects an area of pi/2.

The correct formula is:

  A = +SUM[ A(i) ] &ndash; (n-2) *pi

</div>
---++ Impact Assessment
---++ Notes

This topic: IVOA > WebHome > IvoaDataModel > STC > STC-1_33-Errata > STC-1_33-Erratum-1
Topic revision: r1 - 2018-11-16 - MarkCresitelloDittmar