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https://issues.apache.org/jira/browse/LUCENE-6699?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14906486#comment-14906486
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Nicholas Knize commented on LUCENE-6699:
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I started by packing all 3 values into a 64 bit long - in fact those MAGIC
numbers are still there (MAGIC[7:12]). The problem with this is precision loss
from compressing each value into 21 bits. The decoded values will give, at
best, 3 decimal precision accuracy - which is ~110m at the equator. If you're
fine with course grain accuracy then copy the BitUtil.{interleave |
deinterleave} methods and use MAGIC[7:12]. The code is much simpler with the
accuracy trade-off.
> 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
> Fix For: Trunk, 5.4
>
> Attachments: Geo3DPacking.java, LUCENE-6699.patch, LUCENE-6699.patch,
> LUCENE-6699.patch, LUCENE-6699.patch, LUCENE-6699.patch, LUCENE-6699.patch,
> LUCENE-6699.patch, LUCENE-6699.patch, LUCENE-6699.patch, LUCENE-6699.patch,
> LUCENE-6699.patch, LUCENE-6699.patch, LUCENE-6699.patch, LUCENE-6699.patch,
> LUCENE-6699.patch, LUCENE-6699.patch, LUCENE-6699.patch, LUCENE-6699.patch,
> LUCENE-6699.patch, LUCENE-6699.patch, LUCENE-6699.patch, LUCENE-6699.patch,
> LUCENE-6699.patch, LUCENE-6699.patch, LUCENE-6699.patch, LUCENE-6699.patch
>
>
> 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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