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From "Chris Male (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-2519) SinusoidalProjection returns the incorrect results
Date Tue, 29 Jun 2010 16:08:51 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-2519?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12883596#action_12883596
] 

Chris Male commented on LUCENE-2519:
------------------------------------

+1

Fix makes sense and follows the alg described in wikipedia and found in jhlabs.

> SinusoidalProjection returns the incorrect results
> --------------------------------------------------
>
>                 Key: LUCENE-2519
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2519
>             Project: Lucene - Java
>          Issue Type: Bug
>          Components: contrib/spatial
>            Reporter: Grant Ingersoll
>
> Currently, the SinusoidalProjection does:
> {code}
> public double[] coords(double latitude, double longitude) {
>     double rlat = Math.toRadians(latitude);
>     double rlong = Math.toRadians(longitude);
>     double nlat = rlong * Math.cos(rlat);
>     return new double[]{nlat, rlong};
>     
>   }
> {code}
> But the correct formula (from http://en.wikipedia.org/wiki/Sinusoidal_projection) is:
> {quote}
> x = (gamma - gamma[0]) cos(phi)
> y = phi
> {quote}
> where gamma[0] is assumed to be the prime meridian in this case (0), gamma is the incoming
longitude and phi is the latitude
> Thus, the above code should return:
> {quote}
> {nlat, rlat}
> {quote}

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