[postgis-users] Bug dropping the Z coordinate?

[Paul Ramsey]

Er, rather,

select st_asbinary(st_extent(geom)), st_zmin(geom), st_zmax(geom) from gtable;

? elegance, we don't need no stinking elegance...

P

On Mon, Jan 11, 2010 at 10:35 AM, Paul Ramsey <pramsey at cleverelephant.ca> wrote:
> Just spitballing, since you have to work with what's there, perhaps do
> a st_extent to get x/y then do a second pass getting zmin and zmax?
>
> P
>
> On Mon, Jan 11, 2010 at 8:38 AM, Abram Gillespie
> <abe.gillespie.lists at gmail.com> wrote:
>> OK, I'll ask this then.  What's the best way to get this:
>>
>> select ST_Extent3d(geometry_column) from my_table;
>>
>> Into EWKB w/o losing the Z (or M) coordinate?
>>
>> Doing:
>>
>> select ST_AsEWKB(ST_Extent3D(geometry_column)) from my_table;
>>
>> unfortunately falls prey to the issue we're discussing.
>>
>> Thanks.
>> -Abe
>>
>> On Sun, Jan 10, 2010 at 10:53 PM, Paragon Corporation <lr at pcorp.us> wrote:
>>> As a side note.  ST_Zmax doesn't exist for geometries.  It works because
>>> geometries can be autocast to boxes.
>>>
>>> See matrix
>>> http://www.postgis.org/documentation/manual-svn/ch08.html#PostGIS_TypeFuncti
>>> onMatrix
>>>
>>> -----Original Message-----
>>> From: postgis-users-bounces at postgis.refractions.net
>>> [mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Paragon
>>> Corporation
>>> Sent: Sunday, January 10, 2010 10:50 PM
>>> To: 'PostGIS Users Discussion'
>>> Subject: Re: [postgis-users] Bug dropping the Z coordinate?
>>>
>>> Abe,
>>>
>>> It seems we are flattening the box3d geometry in to a 2D polygon always
>>> instead of as a 3D/2.5D polygon.
>>> I'm not sure it's a bug though, because I think a box3d is an invalid 2.5/3D
>>> polygon if you were to construct it.
>>>
>>> Can you envision it?
>>>
>>> Paul, Mark or Kevin might have a better clue, but I think it's at best an
>>> ambiguous 3D polygon and that is the problem. A box3d isn't really a 3D box,
>>> its more just a coordinate bounding thing.
>>>
>>> Hope that helps,
>>> Regina
>>>
>>> -----Original Message-----
>>> From: postgis-users-bounces at postgis.refractions.net
>>> [mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Abram
>>> Gillespie
>>> Sent: Sunday, January 10, 2010 4:31 PM
>>> To: PostGIS Users Discussion
>>> Subject: [postgis-users] Bug dropping the Z coordinate?
>>>
>>> Is this a bug?
>>>
>>> select ST_ZMax('BOX3D(0 0 0,0 0 1)'::box3d);
>>>
>>> versus
>>>
>>> select ST_ZMax(ST_GeomFromEWKB(ST_AsEWKB('BOX3D(0 0 0,0 0 1)'::box3d)));
>>>
>>> The first query returns "1" as expected but the second returns "0" as
>>> unexpected.
>>>
>>> I'm trying to add Z/M support to zigGIS and this is show-stopping me.
>>> Any work-arounds if this is a bug?  Also, I'll be happy to report the bug if
>>> so.
>>>
>>> Thanks.
>>> -Abe
>>> _______________________________________________
>>> postgis-users mailing list
>>> postgis-users at postgis.refractions.net
>>> http://postgis.refractions.net/mailman/listinfo/postgis-users
>>>
>>>
>>>
>>> _______________________________________________
>>> postgis-users mailing list
>>> postgis-users at postgis.refractions.net
>>> http://postgis.refractions.net/mailman/listinfo/postgis-users
>>>
>>>
>>> _______________________________________________
>>> postgis-users mailing list
>>> postgis-users at postgis.refractions.net
>>> http://postgis.refractions.net/mailman/listinfo/postgis-users
>>>
>> _______________________________________________
>> postgis-users mailing list
>> postgis-users at postgis.refractions.net
>> http://postgis.refractions.net/mailman/listinfo/postgis-users
>>
>