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https://issues.apache.org/jira/browse/SIS-45?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13257764#comment-13257764
]
Peter Karich commented on SIS-45:
---------------------------------
Normalizing the distance leeds to some more (20%) improvements:
{code}
double normedRadius = DistanceUtils.getNormalizedDist(radiusKM);
... queryByPointRadius(point, normedRadius, ..
{code}
{code}
if (DistanceUtils.getNormedHaversineDistance(data[i].getLatLon().getLat(),
data[i]
.getLatLon().getLon(), point.getLat(), point.getLon()) <=
normedRadius) {
matches.add(data[i]);
}
{code}
with:
{code}
public static double getNormedHaversineDistance(double fromLat, double
fromLon, double toLat, double toLon) {
double dLat = Math.toRadians(toLat - fromLat);
double dLon = Math.toRadians(toLon - fromLon);
return 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);
}
public static double getNormalizedDist(double radiusKM) {
double tmp = Math.sin(radiusKM / 2 / EARTH_RADIUS);
return tmp * tmp;
}
{code}
but I still feel bad (programming in the dark without unit tests ...)
> 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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