[postgis-users] PointM, PolyLineM, PolygonM, ...

[strk at refractions.net]

This is a continuation of an old thread about support
for Measured geometries (as supported by shapefiles).

See:
http://postgis.refractions.net/pipermail/postgis-users/2003-February/002149.html

For any type shapefile format supports 3 version:

Type  - x,y
TypeM - x,y,m
TypeZ - x,y,z,m

Current (hwgeom/lwgeom) loader (shp2pgsql) makes these conversions:

Type  -> geometry2d
TypeM -> geometry2d (you loose M!)
TypeZ -> geometry3d (you loose M!)

Current (hwgeom/lwgeom) dumper (pgsql2shp) makes these conversions:

geometry2d -> Type
geometry3d -> TypeZ (you waste space for empty M values !)

Now that postgis supports up to 4 dimensions geometry, what do you
think should be done ? My vision is this:

Type  <-> geometry2d
TypeM <-> geometry3d
TypeZ <-> geometry4d

What do you think ?

--strk;