Hello, So we’ve been collecting gps data for months including the signal strength of the cell signal. We’ve assigned this a strength value of 1 through 5 and null. These are about 19 millions of points that we have recorded. I’d like to clump points within 250 feet of each other in to one polygon.
I used the links below and tried that on a pretty small number and it took it’s time but it worked, assigning a group to the points with the same strength that were within the distance of another point. From that I was able to make a polygon that covered all the points in the same group. http://postgis.17.n6.nabble.com/Determining-clusters-of-points-tt3533366.html#a3533387 or http://answerpot.com/showthread.php?2021386-Determining+clusters+of+points. However, running this against the whole table of points it is taking forever, well days and still running. I recently came across the new indexing with Postgis 2 (http://blog.opengeo.org/2011/09/28/indexed-nearest-neighbour-search-in-postgis/) and thought that this might help with this task. I also was wondering if it would make sense to create 5 sub-tables of points, one for each signal strength? I'm not sure how well the btree and gist indexes play together? Could I do something like taking each point, then run a query for points ordered by distance away from the point in the question and then keep processing rows in a function until the distance exceeds the threshold and then move on to the next point? Thanks, Bryan. _______________________________________________ postgis-users mailing list [email protected] http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users
