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From "David Smiley (JIRA)" <>
Subject [jira] [Commented] (LUCENE-4922) A SpatialPrefixTree based on the Hilbert Curve and variable grid sizes
Date Tue, 23 Apr 2013 15:27:15 GMT


David Smiley commented on LUCENE-4922:

Thanks for the proposal Hatim!  That's a good proposal.  I enjoyed reading some of the research
papers you referenced.  I'm excited to think that at the end of the summer, there's going
to be an awesome optimized PrefixTree; and I'm a tad jealous that a lucky student is going
to build it instead of me :-) 

p.s. I independently developed my own outline of tasks to do, which I'll share with the student
that is accepted (which is likely you but theoretically could be another student if there
is interest from others)
> A SpatialPrefixTree based on the Hilbert Curve and variable grid sizes
> ----------------------------------------------------------------------
>                 Key: LUCENE-4922
>                 URL:
>             Project: Lucene - Core
>          Issue Type: New Feature
>          Components: modules/spatial
>            Reporter: David Smiley
>            Assignee: David Smiley
>              Labels: gsoc2013, mentor, newdev
> My wish-list for an ideal SpatialPrefixTree has these properties:
> * Hilbert Curve ordering
> * Variable grid size per level (ex: 256 at the top, 64 at the bottom, 16 for all in-between)
> * Compact binary encoding (so-called "Morton number")
> * Works for geodetic (i.e. lat & lon) and non-geodetic
> Some bonus wishes for use in geospatial:
> * Use an equal-area projection such that each cell has an equal area to all others at
the same level.
> * When advancing a grid level, if a cell's width is less than half its height. then divide
it as 4 vertically stacked instead of 2 by 2. The point is to avoid super-skinny cells which
occurs towards the poles and degrades performance.
> All of this requires some basic performance benchmarks to measure the effects of these

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