Hi, Not sure, but by subdividing your trajectories, maybe you could index theirs geometries and their time interval to avoid some unneeded calculations ?
Le ven. 15 févr. 2019 à 07:14, Stefan Novak < [email protected]> a écrit : > Hello! > > I'm interested in using PostGIS's support for trajectories to solve a > problem I'm working on. I have a collection of 3D spatiotemporal > trajectories (representing spacecraft orbits) that I'm needing to query for > any close approaches among any pair of trajectories. For my problem, a > close approach occurs when the distance between two trajectories at the > same time/measure falls below a threshold; a close approach can occur > multiple times between a pair of trajectories. Naively, the problem can be > solved by calculating pairwise distances for each epoch, resulting in ~ > n^2/2*t distance calculations (where t is the number of timesteps), but I'm > trying to avoid the n-squared problem. > > I started reading through the docs and was attracted to > ST_ClosestPointOfApproach, however I'm interested in more than just the > point of minimum distance between the trajectories -- it would be ideal to > have multiple closest points of approach. > > Is it possible to use PostGIS to perform this type of query? > > On a related note, is it possible to index trajectory geometries such that > a Cartesian product can be avoided when querying for close approaches > between any pairs of trajectories? > > Thanks for any insight you can share! > > Cheers! > _______________________________________________ > postgis-users mailing list > [email protected] > https://lists.osgeo.org/mailman/listinfo/postgis-users
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