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https://issues.apache.org/jira/browse/SOLR-773?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12632327#action_12632327
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patrick o'leary commented on SOLR-773:
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I believe you guys are using a branch of the code as we were looking at using
the mapquest sids.
Both versions are solving the same basic problem, creating a sudo quad tree
implementation.
com.pjaol was the initial API I built, com.mapquest is donated to us by
MapQuest.
Both versions work by flattening out the earth onto a series of grids, the
grids get progressively smaller
with each _localTierN, in the MapQuest version there is a notion of zooming.
Some quick info graphics here:
http://www.nsshutdown.com/projects/lucene/whitepaper/locallucene_v2.html
The differences are, com.pjaol uses pretty exact measurements, the flattening
method is based on something
called a sinusoidal projection, where I translate lat / longs to x,y
coordinates which provide an equal spaced projection on a flat surface. Then I
use GeoTools for the actual precise distance calculation.
It comes at a slight performance cost to be that exact, but users have a need
for it.
The com.mapquest code, does a direct conversion to cartesian x,y coordinate
from lat / long, encodes and generates sids and uses a standard great circle
equation for distance calculation. So not as convoluted.
It does come at a slight accuracy cost - but only in a few places, Greenland,
New Zealand, some places around the poles and equator.
So it's perfect for web based applications as the +/- error differential is
small enough to be acceptable for most users.
There is however a good audience for local lucene, who use it for more exact
calculation, even down to the meter range. It's also used by some research
groups for non-land based activities hence the desire to retain the exactness.
> Incorporate Local Lucene/Solr
> -----------------------------
>
> Key: SOLR-773
> URL: https://issues.apache.org/jira/browse/SOLR-773
> Project: Solr
> Issue Type: New Feature
> Reporter: Grant Ingersoll
> Priority: Minor
>
> Local Lucene has been donated to the Lucene project. It has some Solr
> components, but we should evaluate how best to incorporate it into Solr.
> See http://lucene.markmail.org/message/orzro22sqdj3wows?q=LocalLucene
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