at UC Berkeley Soda Hall, for the San Francisco PostgreSQL Users Group and again at the College of Natural Resources for GIS Day 2012 main slides and dustymugs’ raster slides errata: * The ST_MakeValid(geom) example could have been expanded to include ST_IsValidDetail() * It is arguably wrong to say that Lat/Lng (EPSG:4326) data is one […]
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KNN Search Speed Test
SYNOPSIS: Using one million randomly generated points, time finding the ten nearest points to the center of the range by using the KNN distance operator versus using a call to PostGIS ST_Distance(). ## Use ST_Distance() explain analyze SELECT ST_Distance(the_geom, ST_GeomFromText(‘POINT(500 500)’)) FROM tgeom ORDER BY ST_Distance(the_geom, ST_GeomFromText(‘POINT(500 500)’)) asc limit 10; Total runtime: 1568.499 ms […]
Check for Validity
SELECT name, state_name, fips, st_summary(the_geom), st_isvalidreason(the_geom) FROM usa_counties WHERE not st_isvalid(the_geom); NOTICE: Ring Self-intersection at or near point -70.82466 42.26050 -[ RECORD 1 ]—-+————————————————- name | Plymouth state_name | Massachusetts fips | 25023 st_summary | MultiPolygon[B] with 1 elements | Polygon[] with 1 rings | ring 0 has 31 points st_isvalidreason | Ring Self-intersection[-70.8246609058028 42.2605069326982] […]