[
Date Prev][
Date Next][
Thread Prev][
Thread Next][
Date Index][
Thread Index]
[
List Home]
|
Re: [geomesa-users] new index -> new implementation for knn-query?
|
Dear Marcel,
Nice graphics! Your second figure is indeed correct: the
KNN algorithm will search all geohashes which could possibly contain
points closer than those already found. However, the first figure is not
accurate, but the fault is mine in choosing a misleading name: the
GeoHashSpiral is not necessarily a spiral made of GeoHashes as your
figure indicated; rather it is a iterator which yields GeoHashes ordered
by their *minimum* geodetic distance from the reference point. Because
of this, the order in which GeoHashes are searched will "jitter" around,
with a striking (yet correct) pattern occurring near the poles in some
cases. Is my explanation clear?
You are correct that the KNN process must be re-implemented in order to
utilize the new z3 index. I ( as the original author ) need to sit down
with some other contributors to see how and when this (quite fun) work
might be done.
Keep the questions coming,
Mike Ronquest
On 09/24/2015 04:59 AM, Marcel wrote:
Hello,
at first I want to thank you all for the last explanations of my
questions. The support is really fast and motivated :)
This leads me to the next question regarding the new index:
When geohashes were not used anymore, a new implemenation for the knn
query should be necessary, because it uses a geohashspiral. In the
attachment you find my understanding for the current execution of a
knn query. First picture shows the geohashspiral and second picture
shows the test whether all points found are really the closest ones.
For this all skin-colored geohashes were processed, because they could
contain some points that are closer to my origin. The small circle
contains the result for k=10. I could imagine that these two pictures
only show a simplified version of the algorithm, but it would be great
if you confirm my understanding is correct. In my masterthesis a want
to explain these method a bit more in detail.
So when a new version comes up, how will this new implemenation look
like? Maybe by starting with a small circle which is growing continously?
Thanks a lot,
Marcel Jacob.
_______________________________________________
geomesa-users mailing list
geomesa-users@xxxxxxxxxxxxxxxx
To change your delivery options, retrieve your password, or unsubscribe from this list, visit
http://www.locationtech.org/mailman/listinfo/geomesa-users
