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https://issues.apache.org/jira/browse/SOLR-2125?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12913363#action_12913363
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Bill Bell commented on SOLR-2125:
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There is another example...
http://www.movable-type.co.uk/scripts/latlong-db.html not sure - but this is
also a good first cut. Then if you want more accurate results calculate results
that come back
and through out ones that are not within. Cache results. The link above
http://janmatuschek.de/LatitudeLongitudeBoundingCoordinates appears a little
more accurate. But this is simpler.
{code}
// first-cut bounding box (in degrees)
$maxLat = $lat + rad2deg($rad/$R);
$minLat = $lat - rad2deg($rad/$R);
// compensate for degrees longitude getting smaller with increasing latitude
$maxLon = $lon + rad2deg($rad/$R/cos(deg2rad($lat)));
$minLon = $lon - rad2deg($rad/$R/cos(deg2rad($lat)));
$sql = "Select ID, Postcode, Lat, Lon
From MyTable
Where Lat>$minLat And Lat<$maxLat
And Lon>$minLon And Lon<$maxLon";
{code}
> Spatial filter is not accurate
> ------------------------------
>
> Key: SOLR-2125
> URL: https://issues.apache.org/jira/browse/SOLR-2125
> Project: Solr
> Issue Type: Bug
> Components: Build
> Affects Versions: 1.5
> Reporter: Bill Bell
> Assignee: Grant Ingersoll
> Attachments: solrspatial.xlsx
>
>
> The calculations of distance appears to be off.
> Note: "The radius of the sphere to be used when calculating distances on a
> sphere (i.e. haversine). Default is the Earth's mean radius in kilometers
> (see org.apache.solr.search.function.distance.Constants.EARTH_MEAN_RADIUS_KM)
> which is set to 3,958.761458084784856. Most applications will not need to set
> this."
> The radius of the earth in KM is 6371.009 km (≈3958.761 mi).
> Also filtering distance appears to be off - example data:
> 45.17614,-93.87341 to 44.9369054,-91.3929348 Approx 137 miles Google. 169
> miles = 220 kilometers
> http://....../solr/select?fl=*,score&start=0&rows=10&q={!sfilt%20fl=store_lat_lon}&qt=standard&pt=44.9369054,-91.3929348&d=280&sort=dist(2,store,vector(44.9369054,-91.3929348))
> asc
> Nothing shows. d=285 shows results. This is off by a lot.
> Bill
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