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https://issues.apache.org/jira/browse/GEOMETRY-71?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17010203#comment-17010203
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Baljit Singh commented on GEOMETRY-71:
--------------------------------------
I tried the solution provided
[here|https://stackoverflow.com/questions/19897187/locating-the-centroid-center-of-mass-of-spherical-polygons].
I wrote the following and it works for both windings:
{code:java}
private Point2S getBarycenter(List<Point2S> list) {
Vector3D sumVector = Vector3D.ZERO;
for (int i = 0; i < list.size(); i++) {
final Vector3D first = list.get(i).getVector();
final Vector3D second = list.get((i + 1) % list.size()).getVector();
sumVector = sumVector.add(first.angle(second),
first.cross(second).normalize());
}
return Point2S.from(sumVector);
}
{code}
So, it seems the algorithm is correct. There is must be a bug somewhere in
calculations. Not totally sure how the above code translates in to ConvexArea2S
etc.
> Investigate Spherical Barycenter Accuracy
> -----------------------------------------
>
> Key: GEOMETRY-71
> URL: https://issues.apache.org/jira/browse/GEOMETRY-71
> Project: Apache Commons Geometry
> Issue Type: Bug
> Reporter: Matt Juntunen
> Priority: Major
> Labels: pull-request-available
> Time Spent: 10m
> Remaining Estimate: 0h
>
> The current code for computing spherical barycenters in
> {{ConvexArea2S.getBarycenter()}} seems to suffer from floating point accuracy
> issues. The {{ConvexArea2STest.checkBarycenterConsistency()}} method checks
> the consistency of the barycenter computation of a region by splitting the
> region into two sections, computing the area and barycenter of each section,
> and then computing the combined barycenter of the sections by adding the
> barycenter of each scaled by its corresponding area. It is expected that the
> combined barycenter computed in this way should equal the barycenter computed
> for the region as a whole. However, in practice, a large epsilon value is
> needed in the comparison in order for the tests to pass. We need to
> investigate why this is the case.
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