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 Yearling
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answered Postgis How to populate column with geography data from geometric data?
Aug
26
revised Find all points within 5m with same name on large dataset
added 6 characters in body
Aug
25
revised Find all points within 5m with same name on large dataset
deleted 2 characters in body
Aug
25
answered Find all points within 5m with same name on large dataset
Aug
20
answered Get points in a union of circles
Aug
17
comment Poor performance with storing large rasters in PostGIS and visualising in QGIS
Ensuring your rasters fit into the page size (as your nice 100x100 small tile size does) is an under-appreciated performance tip. If you have 3 1-byte bands, then you're looking at about a 50x50 tile size. (3 * 50 * 50 = 7500 < 8192 byte page size)
Aug
17
comment Poor performance with storing large rasters in PostGIS and visualising in QGIS
If they load great as a VRT, why didn't you stop there? What gain are you expecting from this great raster journey?
Aug
12
comment Slow Planning for Postgis ST_Intersects
No, the "rows" is not how many will be scanned, it is how many rows the planner thinks the query will return for a given clause. It's the "estimate". Having a good estimate (as PostGIS does) is important for complex query planning, but not important for simple queries, which have simple plans. Run the queries with EXPLAIN ANALYZE to see the difference between estimates and actual.
Aug
12
answered Rasters loaded in Postgres/PostGIS using raster2pgsql contain blank lines
Aug
12
comment Slow Planning for Postgis ST_Intersects
e.g. compare the results of EXPLAIN and EXPLAIN ANALYZE on your query. They should both return the same number of rows, PostGIS's initial guess about the size of the result set will just be more accurate. (Compare estimated vs actual.)
Aug
12
comment Slow Planning for Postgis ST_Intersects
Hm? They scan pretty much exactly the same data, they both have rtree-on-gist indexes that are build and scanned with basically the same code. PostGIS is just doing better at knowing how big the final output set will be, which is irrelevant in your query, but would be useful knowledge if your query was only a part of a much larger SQL expression.
Aug
12
answered Slow Planning for Postgis ST_Intersects
Aug
12
answered Performance Improvement of Postgres vs PostGIS
Aug
12
answered Multipolygon From Multilinestring PostGis
Aug
11
comment Multipolygon From Multilinestring PostGis
You can use ST_ConcaveHull to get approximate polygon. Since the lines don't actually form the boundary of the areas you're going to have some difficulty getting a perfect coverage of polygons from the data. Another possibility is building a line voronoi using the faces and assign faces to categories based on what lines fall within the faces. I don't know that PostGIS hast he functions for that (look at ST_DelaunayTriangles())
Aug
11
comment Multipolygon From Multilinestring PostGis
You haven't described your inputs and outputs and what you get versus what you want particularly well. A picture (or two or three) is worth a thousand words.
Aug
9
comment Aggregate/merge data upon insert into PostGIS (via gdal)
If you ensure the tiles have a bit of overlap to start with you should be able to ST_Union() them at the PostGIS stage w/o too much trouble. Mind you, building huge, complex, raster-derived polygons is contra-indicated for performance in vector processing, so YMMV on processes further downstream.
Aug
5
answered Is the PostGIS st_intersection function viable for very large data-sets?
Aug
3
awarded  Yearling
Aug
2
answered Convert distance from meters to EPSG 3857