> This looks cool, but it raises a question. Are there any operators or

> functions besides the logical "contained within" ones?

Here's a list of the functions provided in the package.

Most of the operators work on the bounding box of the geometries. If

you want more precision, you can use the truly_inside(A,B) function.

Where A=a geometry and B=a bounding box. Note, if you uses a geometry

for B, the function will automatically convert this geometry to a

bounding box.

What kind of operators were you interested in?

length3d(GEOMETRY) - 3d length of all linestrings in GEOMETRY

length2d(GEOMETRY) - 2d length of all linestringsin GEOMETRY

area2d (GEOMETRY) - area of all polygons (projected to the XY plane)

perimeter2d(GEOMETRY) - 2d length of all polygon rings

perimeter3d(GEOMETRY) - 3d length of all polygon rings

truly_inside(GEOMETRY,GEOMETRY) - true if part of A is inside B's

bounding box

A <& B - true if A's bounding box overlaps or is to the right of B's

A << B - true if A's bounding box is strictly to the right of B's

A &> B - true if A's bounding box overlaps or is strictly to the right

of B's

A >> B - true if A's bounding box is strictly to the left of B's

A ~= B - true if A's geometry is the same as B's (order of sub-geometry

unimportant)

A ~ B - true if A's bounding box is contained by B's bounding box

A @ B - true if A's bounding box contains B's bounding box

A && B- true if A's bounding box overlaps B's bounding box

npoints(GEOMETRY) - (info) how many points are in the geometry

nrings(GEOMETRY) - (info) how many rings are there in the geometry

mem_size(GEOMETRY) - (info) how much space does this geometry take up

numb_sub_objs(GEOMETRY) - (info) how many sub objects are inside this

geometry

summary(GEOMETRY) - (info) give a text summary of whats inside the

geometry

> Also, must it be compiled within the contrib directory, or can it be

> compiled separately from the postgresql distribution with a set of

> installed postgresql header files?

Unfortunately, PostGIS requires a proper "postgres.h" for your system.

This is only created if you have a full source distribution.

Since version 7.1, the postgres installation does not include postgres.h

in the installed include files. Basically, to compile any of the

server-side extras, you now need a complete, configured source tree of

the distribution (not that this is too onerous: retreive the source,

./configure).

You can untar the PostGIS distribution somewhere other than contrib, but

you'll have to edit the 'top_builddir' in the Makefile to point to your

postgresql source directory.

dave

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