Difference: STC-1_33-Erratum-1 (1 vs. 7)

Revision 72019-05-08 - MarkCresitelloDittmar

 
META TOPICPARENT name="STC-1_33-Errata"

STC-1.33 Erratum 1:

Author: DM WG

Date last changed: 2019-02-04

Changed:
<
<		Date accepted:
>
>		Date accepted: 2019-04-16
 

Rationale

This erratum is to correct an issue related to POLYGON with different orientations reported at the IVOA interop in Victoria, BC: May 2018

cite (from STC-1.33):

"The summation is over determinants of matrices formed by the position vectors xi of successive vertices; xn+1 = x1. In spherical space (left-handed coordinates) the area is:
A = - SUM[ α(i) ] – (n-2) *piαi are the polygon’s angles at the vertices. Reverse the sign for right-handed coordinates."

Erratum Content

Original Wording

  • 4.5.1.4 page 30
    A = - SUM[ α(i) ] – (n-2) *pi

New Wording

  • 4.5.1.4 page 30
    A = + SUM[ α(i) ] – (n-2) *pi

Impact Assessment

Software using the wrong formula must be updated

Example

A = (RA,DEC)[0] = (90, 0)
B = (RA,DEC)[1] = (0, 0)
C = (RA,DEC)[2] = (0, 90)
The image below shows gaphically that triangle (CCW as seen from inside the sphere, but CW as seen from outside the sphere).

The three angles of the polygon are all 90 deg, or pi/2 rad by construction. The area is indeed: +3 * pi/2 -pi = pi/2 (1/8 of the entire sky)

META FILEATTACHMENT attachment="ABC.png" attr="" comment="" date="1549354042" name="ABC.png" path="ABC.png" size="51935" user="LaurentMichel" version="1"

Revision 62019-02-05 - LaurentMichel

 
META TOPICPARENT name="STC-1_33-Errata"

STC-1.33 Erratum 1:

Author: DM WG

Date last changed: 2019-02-04

Date accepted:

Rationale

This erratum is to correct an issue related to POLYGON with different orientations reported at the IVOA interop in Victoria, BC: May 2018

Changed:
<
<		cite (from STC-S):
>
>		cite (from STC-1.33):
  "The summation is over determinants of matrices formed by the position vectors xi of successive vertices; xn+1 = x1. In spherical space (left-handed coordinates) the area is:
A = - SUM[ α(i) ] – (n-2) *piαi are the polygon’s angles at the vertices. Reverse the sign for right-handed coordinates."

Erratum Content

Original Wording

  • 4.5.1.4 page 30
    A = - SUM[ α(i) ] – (n-2) *pi

New Wording

  • 4.5.1.4 page 30
    A = + SUM[ α(i) ] – (n-2) *pi

Impact Assessment

Software using the wrong formula must be updated

Example

A = (RA,DEC)[0] = (90, 0)
B = (RA,DEC)[1] = (0, 0)
C = (RA,DEC)[2] = (0, 90)
The image below shows gaphically that triangle (CCW as seen from inside the sphere, but CW as seen from outside the sphere).

The three angles of the polygon are all 90 deg, or pi/2 rad by construction. The area is indeed: +3 * pi/2 -pi = pi/2 (1/8 of the entire sky)

META FILEATTACHMENT attachment="ABC.png" attr="" comment="" date="1549354042" name="ABC.png" path="ABC.png" size="51935" user="LaurentMichel" version="1"

Revision 52019-02-05 - LaurentMichel

 
META TOPICPARENT name="STC-1_33-Errata"

STC-1.33 Erratum 1:

Author: DM WG

Changed:
<
<		Date last changed: 2018-11-16
>
>		Date last changed: 2019-02-04
  Date accepted:

Rationale

Changed:
<
<		This erratum is to correct an error reported at the IVOA interop in Victoria, BC: May 2018
>
>		This erratum is to correct an issue related to POLYGON with different orientations reported at the IVOA interop in Victoria, BC: May 2018
 
Deleted:
<
<
 
Changed:
<
<		cite:
>
>		cite (from STC-S):
 
Changed:
<
<		The formula in Section 4.5.1.4 (pg 30: Region.Polygon) states
"The summation is over determinants of matrices formed by the position vectors xi of successive vertices; xn+1 = x1. In spherical space (left-handed coordinates) the area is:
A = - SUM[ α(i) ] – (n-2) *piαi are the polygon’s angles at the vertices. Reverse the sign for right-handed coordinates."
but.
A = (RA,DEC)[0] = (90, 0)
B = (RA,DEC)[1] = (0, 0)
>
>		"The summation is over determinants of matrices formed by the position vectors xi of successive vertices; xn+1 = x1. In spherical space (left-handed coordinates) the area is:
A = - SUM[ α(i) ] – (n-2) *piαi are the polygon’s angles at the vertices. Reverse the sign for right-handed coordinates."
Deleted:
<
<
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 –pi = -5/2 pi One expects an area of pi/2.
The correct formula is:
A = +SUM[ α(i) ] – (n-2) *pi

 

Erratum Content

Original Wording

  • 4.5.1.4 page 30
    A = - SUM[ α(i) ] – (n-2) *pi

New Wording

  • 4.5.1.4 page 30
    A = + SUM[ α(i) ] – (n-2) *pi

Impact Assessment

Software using the wrong formula must be updated

Changed:
<
<

Notes

>
>

Example

 
Changed:
<
<
  • We need to confirm that the example has considered the 'left-handed' vs 'right-handed' qualifiers from the text.
>
>		A = (RA,DEC)[0] = (90, 0)
B = (RA,DEC)[1] = (0, 0)
C = (RA,DEC)[2] = (0, 90)
The image below shows gaphically that triangle (CCW as seen from inside the sphere, but CW as seen from outside the sphere).
Added:
>
>

The three angles of the polygon are all 90 deg, or pi/2 rad by construction. The area is indeed: +3 * pi/2 -pi = pi/2 (1/8 of the entire sky)

META FILEATTACHMENT attachment="ABC.png" attr="" comment="" date="1549354042" name="ABC.png" path="ABC.png" size="51935" user="LaurentMichel" version="1"
 

Revision 42018-12-20 - LaurentMichel

 
META TOPICPARENT name="STC-1_33-Errata"

STC-1.33 Erratum 1:

Author: DM WG

Date last changed: 2018-11-16

Date accepted:

Rationale

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

cite:

Changed:
<
<		The formula in Section 4.5.1.4 (pg 30: Region.Polygon) states
"The summation is over determinants of matrices formed by the position vectors xi of successive vertices; xn+1 = x1. In spherical space (left-handed coordinates) the area is:
A = - SUM[ α(i) ] – (n-2) *piαi are the polygon’s angles at the vertices. Reverse the sign for right-handed coordinates."but.
A = (RA,DEC)[0] = (90, 0)
>
>		The formula in Section 4.5.1.4 (pg 30: Region.Polygon) states
"The summation is over determinants of matrices formed by the position vectors xi of successive vertices; xn+1 = x1. In spherical space (left-handed coordinates) the area is:
A = - SUM[ α(i) ] – (n-2) *piαi are the polygon’s angles at the vertices. Reverse the sign for right-handed coordinates."
but.
A = (RA,DEC)[0] = (90, 0)
B = (RA,DEC)[1] = (0, 0)
Added:
>
>
C = (RA,DEC)[2] = (0, 90)
 
Changed:
<
<		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 –pi = -5/2 pi One expects an area of pi/2.
The correct formula is:
A = +SUM[ α(i) ] – (n-2) *pi
>
>		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 –pi = -5/2 pi One expects an area of pi/2.
The correct formula is:
A = +SUM[ α(i) ] – (n-2) *pi
 
Added:
>
>
 

Erratum Content

Original Wording

  • 4.5.1.4 page 30
    A = - SUM[ α(i) ] – (n-2) *pi

New Wording

  • 4.5.1.4 page 30
    A = + SUM[ α(i) ] – (n-2) *pi

Impact Assessment

Software using the wrong formula must be updated

Notes

  • We need to confirm that the example has considered the 'left-handed' vs 'right-handed' qualifiers from the text.

Revision 32018-12-19 - LaurentMichel

 
META TOPICPARENT name="STC-1_33-Errata"

STC-1.33 Erratum 1:

Author: DM WG

Date last changed: 2018-11-16

Date accepted:

Rationale

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

Changed:
<
<

Erratum Content

>
>
 
Changed:
<
<		The formula in Section 4.5.1.4 (pg 30: Region.Polygon) states:
>
>		cite:
Deleted:
<
<
 
Changed:
<
<		"The summation is over determinants of matrices formed by the position vectors xi of successive vertices; xn+1 = x1. In spherical space (left-handed coordinates) the area is:
>
>		The formula in Section 4.5.1.4 (pg 30: Region.Polygon) states
"The summation is over determinants of matrices formed by the position vectors xi of successive vertices; xn+1 = x1. In spherical space (left-handed coordinates) the area is:
A = - SUM[ α(i) ] – (n-2) *piαi are the polygon’s angles at the vertices. Reverse the sign for right-handed coordinates."but.
A = (RA,DEC)[0] = (90, 0)
 
Changed:
<
<		A = - SUM[ α(i) ] – (n-2) *pi
>
>		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 –pi = -5/2 pi One expects an area of pi/2.
The correct formula is:
A = +SUM[ α(i) ] – (n-2) *pi
Deleted:
<
<

αi are the polygon’s angles at the vertices. Reverse the sign for right-handed coordinates."

 
Changed:
<
<		 but..


A = (RA,DEC)[0] = (90, 0)

>
>

Erratum Content

Original Wording

  • 4.5.1.4 page 30
    A = - SUM[ α(i) ] – (n-2) *pi
Deleted:
<
<		 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 –pi = -5/2 pi

One expects an area of pi/2.

The correct formula is:

A = +SUM[ α(i) ] – (n-2) *pi

 
Changed:
<
<
>
>

New Wording

Added:
>
>
  • 4.5.1.4 page 30
    A = + SUM[ α(i) ] – (n-2) *pi
 

Impact Assessment

Added:
>
>		 Software using the wrong formula must be updated
 

Notes

  • We need to confirm that the example has considered the 'left-handed' vs 'right-handed' qualifiers from the text.

Revision 22018-11-18 - MarkCresitelloDittmar

 
META TOPICPARENT name="STC-1_33-Errata"

STC-1.33 Erratum 1:

Author: DM WG

Date last changed: 2018-11-16

Date accepted:

Rationale

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

Added:
>
>
 

Erratum Content

Changed:
<
<		The formula in 4.5.1.4 states:
>
>		The formula in Section 4.5.1.4 (pg 30: Region.Polygon) states:
Added:
>
>
 
Changed:
<
<		 “A = - SUM[ A(i) ] – (n-2) *pi“
>
>		"The summation is over determinants of matrices formed by the position vectors xi of successive vertices; xn+1 = x1. In spherical space (left-handed coordinates) the area is:
 
Changed:
<
<		but:
A = (RA,DEC)[0] = (90, 0)
>
>		A = - SUM[ α(i) ] – (n-2) *pi
 
Changed:
<
<		 B = (RA,DEC)[1] = (0, 0)
>
>
 
Changed:
<
<		 C = (RA,DEC)[2] = (0, 90)
>
>		αi are the polygon’s angles at the vertices. Reverse the sign for right-handed coordinates."
 
Changed:
<
<		The three angles of the polygon are all 90 deg, or pi/2 rad by construction.
>
>
 
Changed:
<
<		A in the above case is: -3 * pi/2 –pi = -5/2 pi
>
>		but..
 
Changed:
<
<		One expects an area of pi/2.
>
>
A = (RA,DEC)[0] = (90, 0)
 
Added:
>
>		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 –pi = -5/2 pi

One expects an area of pi/2.

 The correct formula is:
Changed:
<
<		 A = +SUM[ A(i) ] – (n-2) *pi
>
>		A = +SUM[ α(i) ] – (n-2) *pi
 
Added:
>
>
 

Impact Assessment

Notes

Added:
>
>
  • We need to confirm that the example has considered the 'left-handed' vs 'right-handed' qualifiers from the text.
 

Revision 12018-11-16 - MarkCresitelloDittmar

 
META TOPICPARENT name="STC-1_33-Errata"

STC-1.33 Erratum 1:

Author: DM WG

Date last changed: 2018-11-16

Date accepted:

Rationale

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

Erratum Content

The formula in 4.5.1.4 states:

“A = - SUM[ A(i) ] – (n-2) *pi“

but:
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 –pi = -5/2 pi

One expects an area of pi/2.

The correct formula is:

A = +SUM[ A(i) ] – (n-2) *pi

Impact Assessment

Notes

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