[postgis-users] I'm missing something

Tue May 20 14:33:31 PDT 2008

I've been attempting these operations using WKB not text.

Perhaps, that's the problem.

Bob

----- Original Message ----- 
From: "Kevin Neufeld" <kneufeld at refractions.net>
To: "PostGIS Users Discussion" <postgis-users at postgis.refractions.net>
Sent: Tuesday, May 20, 2008 2:07 PM
Subject: Re: [postgis-users] I'm missing something

>I don't receive an error when merging your geometries together.
>
> create table tmp (geom geometry);
> insert into tmp values ('MULTILINESTRING((46 34.25,80 34.25))'::geometry);
> insert into tmp values ('MULTILINESTRING((80 34.25,80 60))'::geometry);
> insert into tmp values ('MULTILINESTRING((46 60,46 34.25))'::geometry);
> select astext(st_union(geom)) from tmp;
>
>                                  astext
> ------------------------------------------------------------------------
>  MULTILINESTRING((46 60,46 34.25),(80 34.25,80 60),(46 34.25,80 34.25))
> (1 row)
>
> -- Kevin
>
> Bob Pawley wrote:
>> I've attached an sql dump of the table tank_lin.
>>
>> Hope this helps.
>>
>> Bob
>>
>>
>>
>> ----- Original Message ----- From: "Paul Ramsey" 
>> <pramsey at cleverelephant.ca>
>> To: "PostGIS Users Discussion" <postgis-users at postgis.refractions.net>
>> Sent: Tuesday, May 20, 2008 1:21 PM
>> Subject: Re: [postgis-users] I'm missing something
>>
>>
>>> Attach the shape file to a bug in the bug tracker and I will have a 
>>> look.
>>>
>>> http://code.google.com/p/postgis/issues/list
>>>
>>> P
>>>
>>> On Tue, May 20, 2008 at 1:12 PM, Bob Pawley <rjpawley at shaw.ca> wrote:
>>>> They are three lines that, on Quantum GIS, display as a flat U - a 
>>>> simple
>>>> tank. Using either tank_lin or process_dgn tables - exactly what I 
>>>> imported
>>>> using dxf2postgis.
>>>>
>>>> 'Select as text' returns three rows each with the expression
>>>> "Multilinestrings" followed by brackets and coordinates.
>>>>
>>>> 'Select St_Union' returns - unknown geometry error.
>>>>
>>>> Are you thinking there is something wrong with the installation?
>>>>
>>>> Bob
>>>>
>>>>
>>>> ----- Original Message ----- From: "Obe, Regina" 
>>>> <robe.dnd at cityofboston.gov>
>>>> To: "PostGIS Users Discussion" <postgis-users at postgis.refractions.net>
>>>> Sent: Tuesday, May 20, 2008 11:51 AM
>>>> Subject: RE: [postgis-users] I'm missing something
>>>>
>>>>
>>>> Are these big geometries?  What does
>>>>
>>>> SELECT ST_AsText(the_geom)
>>>>   FROM tank_lin;
>>>>
>>>> Also just to rule out its the table you are inserting into  - does the
>>>> Union without inserting work?
>>>>
>>>> Select   ST_Union(the_geom)
>>>> from tank_lin;
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> ________________________________
>>>>
>>>> From: postgis-users-bounces at postgis.refractions.net
>>>> [mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Bob
>>>> Pawley
>>>> Sent: Tuesday, May 20, 2008 2:11 PM
>>>> To: PostGIS Users Discussion
>>>> Subject: Re: [postgis-users] I'm missing something
>>>>
>>>>
>>>> Hi Regina
>>>>
>>>> It gives me three rows each with the expression "ST_MultiLineString"
>>>> with nothing else.
>>>>
>>>> Bob
>>>>
>>>> ----- Original Message ----- From: Obe, Regina
>>>> <mailto:robe.dnd at cityofboston.gov>
>>>> To: PostGIS Users Discussion
>>>> <mailto:postgis-users at postgis.refractions.net>
>>>> Sent: Tuesday, May 20, 2008 10:56 AM
>>>> Subject: RE: [postgis-users] I'm missing something
>>>>
>>>> Bob,
>>>>
>>>> Strange. I don't think I have ever seen quite that error before.
>>>> What does
>>>>
>>>> SELECT ST_GeometryType(the_geom)
>>>> FROM tank_lin;
>>>>
>>>> give you?
>>>>
>>>> Regina
>>>>
>>>> ________________________________
>>>>
>>>> From: postgis-users-bounces at postgis.refractions.net on behalf of
>>>> Bob Pawley
>>>> Sent: Tue 5/20/2008 1:07 PM
>>>> To: PostGIS Users Discussion
>>>> Subject: Re: [postgis-users] I'm missing something
>>>>
>>>>
>>>>
>>>> I tried this -
>>>>
>>>> Insert into graphics.process_dgm(the_geom)
>>>> Select   ST_Union(the_geom)
>>>> from tank_lin;
>>>>
>>>> and got the error "Unknown geometry type: 0"
>>>>
>>>> Bob
>>>> ----- Original Message -----
>>>> From: "Paul Ramsey" <pramsey at cleverelephant.ca>
>>>> To: "PostGIS Users Discussion"
>>>> <postgis-users at postgis.refractions.net>
>>>> Sent: Tuesday, May 20, 2008 9:51 AM
>>>> Subject: Re: [postgis-users] I'm missing something
>>>>
>>>>
>>>>> You don't want the GROUP BY. It is grouping the union op on
>>>>
>>>> distinct
>>>>>
>>>>> geometry... ie, one per row. Remove it and you'll get what you
>>>>
>>>> want,
>>>>>
>>>>> one output row.
>>>>>
>>>>> P
>>>>>
>>>>> On Tue, May 20, 2008 at 8:49 AM, Bob Pawley <rjpawley at shaw.ca>
>>>>
>>>> wrote:
>>>>>>
>>>>>> Hi
>>>>>>
>>>>>> I am attemptijng to use the ST_Union function to collapse
>>>>
>>>> three rows from
>>>>>>
>>>>>> a
>>>>>> table called tank_lin into one row in table called
>>>>
>>>> process_dgm.
>>>>>>
>>>>>> Here's what I used -
>>>>>> Insert into graphics.process_dgm(the_geom)
>>>>>> Select   ST_Union(the_geom)
>>>>>> from tank_lin
>>>>>> Group by tank_lin.the_geom;
>>>>>>
>>>>>> The result is three rows inserted into process_dgm, each row
>>>>
>>>> appearing to
>>>>>>
>>>>>> be
>>>>>> simple copies of each of the original rows.
>>>>>> I also attempted group by another column but received error
>>>>
>>>> 'unknown
>>>>>>
>>>>>> geometry'.
>>>>>>
>>>>>> I also tried STR_LineMerge with similar results.
>>>>>>
>>>>>> What am I not considering?
>>>>>>
>>>>>> Bob
>>>>>> _______________________________________________
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>>>>>>
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