I've only just come to PostGIS, although I have a bit of PostgreSQL
experience, and I'm rapidly being overwhelmed by the volume of choices
available. So I thought I'd describe my problem in hopes that more
experienced folks could make some useful suggestions:
I've got ~1.2 million entities with location information in lat/long
format, and I've been tasked with adding the ability to search based on
distance (in m or km) from a user-specified point to the existing search
capabilities. It looks like to do this with PostGIS I need to add
another column to my table using |AddGeometryColumn(),| but I'm not sure
what SRID I should be using. My data are roughly bounded by latitude
-10 to -50 and longitude 110-160 (Australia), which puts UTM 53J right
in the middle, but I'm uncertain as to how much distortion that would
suffer at the edges. Would I be best off converting my lat/long pairs
to WGS84, and building some kind of index on that (typically I'd be
looking for things in a range around 20km, but could be as much as
400km)? Or should I stay with lat/long and use spherical distance
calculations? Is there something clever I could do to create
distance-based indices, or should I just stick with a bounding box on
lat/long?
Sorry to have so many n00b questions, but any pointers would be appreciated.
Thanks,
Steve.
--
Stephen Baillie
Developer
Alliance Software
1/234 Whitehorse Road
Nunawading, VIC 3131
Australia
Ph: 03 9877 9921
Fax: 03 9894 2106
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