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From "Karl Wright (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LUCENE-7970) Improve generation of circle plane
Date Thu, 21 Sep 2017 12:44:00 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-7970?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16174675#comment-16174675
] 

Karl Wright commented on LUCENE-7970:
-------------------------------------

[~ivera] I think this is a good addition to the stable of circle implementations, and I like
how you solve the problem in a way that's as cheap as possible.

I have a few things that we should discuss:

(1) For the initial computation of the inner and outer planes, I would like more comments
that explain exactly what the math is behind the construction of these planes.  It's currently
unclear where that came from and I think we really need to know it.

(2) The getBounds() method shouldn't bother being exact; it should just use the outer plane
(if present), or the inner plane (if not present) to set the bounds.  Bounds are defined as
possibly being larger than the shape they contain, so that is OK.  Also, we need to be sure
xyz bounds work OK as well; just doing points doesn't work for XYZ bounds -- you need the
planes too.  Maybe you can just use both planes; that would be safest.

(3) We shouldn't make the class public; it should be class scoped.  Instead, add a factory
method to GeoCircleFactory.

Thanks!!


> Improve generation of circle plane 
> -----------------------------------
>
>                 Key: LUCENE-7970
>                 URL: https://issues.apache.org/jira/browse/LUCENE-7970
>             Project: Lucene - Core
>          Issue Type: Improvement
>          Components: modules/spatial3d
>            Reporter: Ignacio Vera
>            Assignee: Karl Wright
>         Attachments: LUCENE_7970.patch, LUCENE-7970.patch, LUCENE-7970-proposed.patch
>
>
> Hi [~Karl wright],
> How circles are currently build do not behave very well when the planet model is not
an sphere. when you are close to the border in WGS84 you might get false positves or false
negatives when checking if a point is WITHIN. I think the reason is how the points to generate
the circle plane are generated which assumes a sphere.
> My proposal is the following:
> Add a new method to PlanetModel:  
> public GeoPoint pointOnBearing(GeoPoint from, double dist, double bearing);
> Which uses and algorithm that takes into account that the planet might not be spherical.
For example Vincenty's formulae (https://en.wikipedia.org/wiki/Vincenty%27s_formulae).
> Use this method to generate the points for the circle plane. My experiments shows that
this approach removes false negatives in WGS84 meanwhile it works nicely in the Sphere.
> Does it make sense?



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