[postgis-users] Question on GEOMETRY type

Paul Ramsey pramsey at opengeo.org
Wed May 19 07:43:03 PDT 2010

If you have an older version of PostGIS, the zmflag() function also
returns the information you need.


2010/5/19 Paul Ramsey <pramsey at opengeo.org>:
> 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
> for.
> P
> 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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