[GRASS5] Re: An internal db for GRASS

Eric G . Miller egm2 at jps.net
Sat Feb 10 15:04:06 EST 2001

On Sat, Feb 10, 2001 at 12:41:30PM -0700, Roger S. Miller wrote:
> Forgive my ignorance, but...
> Rich Shepard wrote:
> > > 2. It does not have spatial data structures. Just now there are flat
> > > record/hash table/BTree options. It would be nice to have a system with
> > > largely consistent features but give a wide variety of choices for the
> > > type of key to use, including spatial types.
> > 
> >   If we're looking at a dbms for attribute data, I still like postgres. But,
> > my understanding of the objections to postgres is that it doesn't handle
> > spatial data structures. Apparently, Berkeley DB doesn't either. So, what do
> > we gain by using it?
> Postgres handles geometric data -- points, circles, polylines, polygons
> and so on -- and includes functions to determine if a point is in an
> area, two lines intersect and others (but no sort of raster
> functionality).  How different is that from handling spacial data
> structures?  Are those structures something that for some reason
> couldn't be addressed as a user-defined type?

Problem is, it treats everything as Cartesian coordinates, which is
wrong for lat/long calculations.  There's also no enforcement of
important things like making sure polylines or polygons don't intersect
themselves (i.e. should be split at a node).  Furthermore, there's no
conception of islands/holes for polygons.

> >   With postgres for attribute data we have a GPL application that runs on
> > almost all platforms and is well documented and well supported.
> I was of the impression that Postgres was under a Berkeley license, not
> GPL.  Is the distinction significant?

Berkeley license is compatible with GPL (mostly).

Difference between PostgreSQL and Berkeley DB are huge.  Ones a client
server database management system, the other is a library with some
functions for managing DB files that treats all user data except keys 
opaquely.  I'm a little worried about using Berkeley DB because, I
understand, the files it creates are machine specific (i.e. not

Eric G. Miller <egm2 at jps.net>

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