I am currently using Solr 5.5.2 and implementing a GeoSpatial search that
returns results within a radius in Km of a specified LatLon. Using a field of
type solr.LatLonType and a geofilt query this gives good results but is much
slower than our regular queries. Using a bbox query is faster but of course
less accurate.
I then attempted to use a field of type
solr.SpatialRecursivePrefixTreeFieldType to check performance and because I
want to be able to do searches within a polygon eventually. The field is
defined as follows
<fieldType name="location_rpt"
class="solr.SpatialRecursivePrefixTreeFieldType"
spatialContextFactory="com.spatial4j.core.context.jts.JtsSpatialContextFactory"
geo="true" distErrPct="0.05" maxDistErr="0.2"
distanceUnits="kilometers" autoIndex="true"/>
<dynamicField name="*__location_rpt" type="location_rpt" indexed="true"
stored="true" multiValued="false" omitNorms="true" />
I'm just using it to index single points right now. The problem is that the
distance calculation is not working correctly. It seems to overstate the
distances for differences in longitude.
For example a query for
&fl=Id,LatLonRPT__location_rpt,_dist_:geodist()&sfield=LatLonRPT__location_rpt&pt=53.409490
-2.979677&query={!geofilt sfield=LatLonRPT__location_rpt pt="53.409490
-2.979677" d=25} returns
{
"Id": "HAR/CH1/80763270",
"LatLonRPT__location_rpt": "53.2 -2.916666",
"_dist_": 24.295607
},
{
"Id": "HAR/CH42/1918283949",
"LatLonRPT__location_rpt": "53.393239 -3.028859",
"_dist_": 5.7587695
}
The true distances for these results are 23.67 and 3.73 km and other results at
a true distance of 17 km aren't returned within the 25 km radius.
The explain has the following
+IntersectsPrefixTreeQuery(IntersectsPrefixTreeQuery(fieldName=LatLonRPT__location_rpt,queryShape=Circle(Pt(x=53.40949,y=-2.979677),
d=0.2° 25.00km),detailLevel=6,prefixGridScanLevel=7))
Is my set up incorrect in some way or is the
SpatialRecursivePrefixTreeFieldType not suitable for doing radius searches on
points in this way?
Thanks in anticipation for any suggestions.
Peter Lancaster.
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