[postgis-users] PointM, PolyLineM, PolygonM

[strk]

Frank,
you are definetively right, sorry for the confusion.
This means that shp2pgsql already (un)supports M values, right ?

If this is the case shp2pgsql could just discard M values from
PointM, PolyLineM and PolygonM like it does with PointZ, PolyLineZ
and PolygonZ. 

.. for the general support we still have frank's array short-term
solution and XYMZ geometry structure redefinition one ..

--strk;

warmerdam wrote:
> strk wrote:
> > pramsey wrote:
> > 
> >>Is is possible to have measure *and* elevation in a shapefile? XYZM? Or 
> >>is it only XYZ and XYM?
> >>Paul
> > 
> > 
> > I think it is *NOT* possible.
> > 
> >>From the Shapefile Format Specification this is the list of known shapes:
> > 	
> > 	Value   Shape Type
> > 	0	Null Shape
> > 	1    	Point
> > 	3    	PolyLine
> > 	5    	Polygon
> > 	8    	MultiPoint
> > 	11    	PointZ
> > 	13    	PolyLineZ
> > 	15    	PolygonZ
> > 	18    	MultiPointZ
> > 	21    	PointM
> > 	23    	PolyLineM
> > 	25    	PolygonM
> > 	28    	MultiPointM
> > 	31    	MultiPatch
> > 
> > I think using the Z field could be ok, but we need a function that tell
> > us wheater a geometry is 2d,3d or measured.  Does OGC say anything about
> > measures ? The array option might also work as a temporary solution, as
> > would do a just-drop-measure approach.
> > ... shp2pgsql could give a few options (--measured-policy=[array|discard])
> 
> Strk,
> 
> The March 1998 version of the Shapefile specification clearly shows that
> the "Z" forms such as PolyLineZ can have Z coordinates *and* M measures
> (see circa page 18), so geometries can have Z and M.
> 
> OGC's simple features specifications do not address "measures".  It might be
> addressed in GML 3.  Measures are supported in some manner by Oracle if you
> wanted something to compare to.  I don't know the details though.
> 
> Best regards,
> 
> -- 
> ---------------------------------------+--------------------------------------
> I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
> light and sound - activate the windows | http://pobox.com/~warmerdam
> and watch the world go round - Rush    | Geospatial Programmer for Rent
> 
> 
> 
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