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https://issues.apache.org/jira/browse/LUCENE-6699?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14644204#comment-14644204
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Karl Wright commented on LUCENE-6699:
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Hi Mike,
The coordinates you'd need to store for geospatial3d are: (x,y,z), rather than
(lat,lon,z). The values are floating-point numbers that range between -1.0 and
1.0 for a sphere, and slightly more than that in abs value for a WGS84
ellipsoid.
There was a ticket where I attached code for a packing scheme that would ram
all three values into a 64-bit long; I'll see if I can find it. That packing
scheme basically gave you resolution of about a meter. However, as you have
pointed out, it's not strictly necessary to stick to 64-bit longs either, so
you're free to propose anything that makes sense. ;-)
> Integrate lat/lon BKD and spatial3d
> -----------------------------------
>
> Key: LUCENE-6699
> URL: https://issues.apache.org/jira/browse/LUCENE-6699
> Project: Lucene - Core
> Issue Type: New Feature
> Reporter: Michael McCandless
> Assignee: Michael McCandless
>
> I'm opening this for discussion, because I'm not yet sure how to do
> this integration, because of my ignorance about spatial in general and
> spatial3d in particular :)
> Our BKD tree impl is very fast at doing lat/lon shape intersection
> (bbox, polygon, soon distance: LUCENE-6698) against previously indexed
> points.
> I think to integrate with spatial3d, we would first need to record
> lat/lon/z into doc values. Somewhere I saw discussion about how we
> could stuff all 3 into a single long value with acceptable precision
> loss? Or, we could use BinaryDocValues? We need all 3 dims available
> to do the fast per-hit query time filtering.
> But, second: what do we index into the BKD tree? Can we "just" index
> earth surface lat/lon, and then at query time is spatial3d able to
> give me an enclosing "surface lat/lon" bbox for a 3d shape? Or
> ... must we index all 3 dimensions into the BKD tree (seems like this
> could be somewhat wasteful)?
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