[jira] [Created] (LUCENE-7158) Haversin should use the earth's mean radius, not its max (equitorial)?

["Michael McCandless (JIRA)" <ji...@apache.org>]

Michael McCandless created LUCENE-7158:
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             Summary: Haversin should use the earth's mean radius, not its max (equitorial)?
                 Key: LUCENE-7158
                 URL: https://issues.apache.org/jira/browse/LUCENE-7158
             Project: Lucene - Core
          Issue Type: Improvement
            Reporter: Michael McCandless


Across our spatial modules we seem to disagree about the earth's radius when we model it as a sphere.

I think in our haversin implementation we use equitorial (maximum) radius, but maybe in spatial3d we use the earth's mean radius.

I think mean makes more sense: the earth is actually a squashed sphere, so it's polar radius is shorter than its equitorial radius.

I think it's important, when we model the earth as a sphere, that we pick one radius and try to use that one consistently?



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