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From "Hatim Hakeel (JIRA)" <>
Subject [jira] [Commented] (LUCENE-4922) A SpatialPrefixTree based on the Hilbert Curve and variable grid sizes
Date Tue, 23 Apr 2013 07:05:16 GMT


Hatim Hakeel commented on LUCENE-4922:

Hi David,

Thanks for the feedback. I have drafted a proposal based on your comments and stuff I figured
out by digging into the background.

Hope it satisfies the requirements of the project. 

> 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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