[postgis-users] Question on GEOMETRY type

Paul Ramsey pramsey at opengeo.org
Wed May 19 07:36:39 PDT 2010

ST_NDims() returns the number of dimensions, but that doesn't
distinguish between XYM and XYZ.
The ESRI compatibility functions SE_IsMeasured() and SE_Is3D() (hey,
they are useful after all!) return the information you are looking


On Wed, May 19, 2010 at 7:23 AM, 孙琦 <qsundw at gmail.com> wrote:
> Can anyone throw some lights on the question?
> Thanks,
> Cheney
> On Wed, May 19, 2010 at 6:27 PM, 孙琦 <qsundw at gmail.com> wrote:
>> Hi experts,
>> Do we have a way to resolve the third dimensionality of GEOMETRY data? As
>> known, those single types(POINT, LINESTRING, POLYGON....) all have the
>> corresponding XYM versions with suffix M. Thus, if we have
>> three-dimensionality feature, we can discriminate its third dimensionality
>> as Z or M by the returned geometry type. However, if the mixed-typed
>> (GEOMETRY) is used, it seems that it's hard to resolve the 3rd
>> dimensionality. By the Postgis 1.5.1 manual, no GEOMETRYM type is provided
>> to fix the issue. So can someone tell me if there is another way to do the
>> work?
>> Thanks,
>> Cheney
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