Monthly Archives: March 2016

[oracle] avoiding SLOW sdo_aggr_union

There is this recurring problem we have in GIS: getting road-segments and wanting to show complete roads. The naive approach would we to do something like the following: insert into street_geoms select ro.rd_ro_ident, ro.rd_ro_name, ro.com_code, ssdo_aggr_union(sdoaggrtype(rd.ro_geometry, 0.005)) as geom from rd_road ro, rd_ro_sec ros where ros.rd_ro_ident = ro.rd_ro_ident group by ro.rd_ro_ident, ro.rd_ro_name, ro.com_code; For good […]

[ORACLE] updating coordinate systems’ definition

We are in the process of migrating an old GIS system. For our new systems we use POSTGIS. But this one still uses oracle. The data is spanning two countries: Belgium and the Netherlands. Our system does something awful: all data is stored in RD (the dutch coordinate system, using Oracle SRID 90112). So how […]