[postgis] Big Database

Roderick A. Anderson raanders at tincan.org
Tue Oct 9 15:29:45 PDT 2001

Several weeks ago I started (again) asking questions about coordinate
systems and PostGIS.  The plan was to test the feasibility of a Regional
level database - the Inland Northwest (north Idaho, east Washington,
west Montana, north Wyoming.)  I have about 170 USGS quads of
Cartgraphic Feature File data (CFF) and the same amount of USGS DEMs
all in UTM zone 11N.
   The DEMs proved to be too much.  I ran out of disk space on my test
system at about 7 million points and besides how do you test PostGIS
when all you're querying is points.

The CFF data was more interesting but only worked out to about 200K
tuples of line data.  So I went looking for more data.  Found a bunch of
free stuff but was disappointed to see it was in LAT/LONG making it less
than optimal for combining with my zone 11N stuff.  8-(
   I'm now at the point of figuring out how to get the two of them into
one 'coordinate' system so I can crank up the tuple count up.

While doing this I think a found a problem with PostGIS - or actually
OpenGIS. If I understand it correctly you can only have one data type;
point, line, polygon, in one coordinate system; UTM 11N in a table.
   This seems to go along with the way most GIS software wants to handle
the data but is kind of limiting from a database perspective.  If I want
all the data in an area (BOX) why do I have to query several tables? And
shouldn't my GIS or COGO software transform the data to whatever system
it (or I) want it in.  I see a way around some of these limitations but
it would be a kludge (use UNIONs) and could fail on a REALLY big query.

So I'm still looking and testing but wanted to let those that have been
so helpful know that I hadn't stopped working on this.

ps.  Anyone have a method to get PROJ4 to convert a file full of
coordinates?  It isn't readily apparent from the man page.


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