[ https://issues.apache.org/jira/browse/SIS-45?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13257774#comment-13257774 ]
Peter Karich commented on SIS-45:
---------------------------------
Now I understand why the time is always the same ... because searchRegion is calculated wrong. It should somehow depend on the radius which will again improve query time a lot!
In my own quadtree implementation (http://karussell.github.com/GraphHopper/) I have this:
{code}
public BBox createBBox(double lat, double lon, double radiusInKm) {
if (radiusInKm <= 0)
throw new IllegalArgumentException("Distance cannot be 0 or negative! " + radiusInKm + " lat,lon:" + lat + "," + lon);
// length of a circle at specified lat / dist
double dLon = (360 / (calcCircumference(lat) / radiusInKm));
// length of a circle is independent of the longitude
double dLat = (360 / (CalcDistance.C / radiusInKm));
// Now return bounding box in coordinates
return new BBox(lat + dLat, lon - dLon, lat - dLat, lon + dLon);
}
{code}
but it is not copy and pastable due to different bounding box definitions
> Performance improvement of queryByPointRadius
> ---------------------------------------------
>
> Key: SIS-45
> URL: https://issues.apache.org/jira/browse/SIS-45
> Project: Spatial Information Systems
> Issue Type: Improvement
> Reporter: Peter Karich
>
> If I didn't make a mistake a search with the normal distance method took ~2.4s and with this distance method it takes only about 0.7s:
> {code}
> public static double getHaversineDistance(double fromLat, double fromLon, double toLat, double toLon) {
> double dLat = Math.toRadians(toLat - fromLat);
> double dLon = Math.toRadians(toLon - fromLon);
> double a = Math.sin(dLat / 2) * Math.sin(dLat / 2)
> + Math.cos(Math.toRadians(fromLat)) * Math.cos(Math.toRadians(toLat)) * Math.sin(dLon / 2) * Math.sin(dLon / 2);
> return EARTH_RADIUS * 2 * Math.asin(Math.sqrt(a));
> }
> {code}
> Also one should think about normalizing the distance before the search so that one does not need the whole last line which should give further speed improvements.
> I'm still unsure why it takes roughly the same time in my example for 10km, 20km and 40kmm where at every step a lot more nodes are involved. Normally I would say the mode nodes - the more comparisons it'll take and the slower it should get. But it doesn't. Probably I'm measuring wrong?
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