[postgis-users] Data storage w.r.t. projections

[Greg Troxel]

  I wonder if anyone has thoughts on which projection I should use to
  store my data? All the Minnesota data will be in UTM zone 15, so this
  seems like a natural choice. I am wondering, however, if it is more
  flexible to store in a projectionless (lat, long) format.

One step that's likely useful is to look at the data sources you will
use and see what they are in.  Most states have a state plane
coordinate system.  I don't mean you should just use that system, but
it seems like information you should know when choosing.

Note also that 'UTM zone 15' still needs a datum; NAD27 CONUS and
WGS84/NAD83 are both commonly used with UTM.

  As I understand it, one of the big advantages of UTM is that is allows
  for Euclidean geometry, as compared to spatial geometry that would be
  required for a lat,long format. Does PostGIS use this feature of UTM
  when computing Distance(), etc?

That's a good question, and also what coordinate system the bounding
box calculations are in.
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