[postgis-users] couldn't get the correct projected values

Fri May 16 11:15:22 PDT 2008

But Regina's thought was that this *was* the original geometry, just  
not documented as such by setting the SRID. That was the basis for my  
comment.

-- Andy

On May 16, 2008, at 1:46 PM, Burgholzer,Robert wrote:

> Andy,
>> fix the original table:
>> 	update il_izmir3 set the_geom = ST_SetSRID(the_geom, 4326);
>
> Unfortunately, no.  As Regina pointed out, all this does is to  
> change the SRID number, it doesn't actually transform (reproject,  
> that is) the geometry.  SetSRID is usually used when importing from  
> some WKT or other geometry operation that yields a geom descriptot  
> without an SRID set (or possibly with an improper one set).
>
> To be honest, I would be surprised if "set the_geom = setSRID 
> (the_geom)" did not yield an error, as the table is created with  
> rules that mandate the geometry be of a certain SRID to prevent you  
> from inadvertently mixing shapes with different SRIDs in a given  
> table.  At least, this is the default behaviour if you create your  
> tables from shapefiles (shp2pgsql).
>
> The one thing I have found lacking (perhaps if I was truly  
> bothered, I would write a function), is a function such as  
> "transformGeomCol(geomcolname, newSrid)" which would update the  
> Restriction on the column and then execute a transform on the  
> column.  When I first started using PostGIS I imported a whole  
> bunch of shapefiles and neglected to set the SRID, and then had to  
> go back later and manually redefine everything.
>
> Robert W. Burgholzer
> Surface Water Modeler
> Office of Water Supply and Planning
> Virginia Department of Environmental Quality
> rwburgholzer at deq.virginia.gov
> 804-698-4405
> Open Source Modeling Tools:
> http://sourceforge.net/projects/npsource/
>
> -----Original Message-----
> From: postgis-users-bounces at postgis.refractions.net [mailto:postgis- 
> users-bounces at postgis.refractions.net] On Behalf Of Andy Anderson
> Sent: Friday, May 16, 2008 11:38 AM
> To: PostGIS Users Discussion
> Subject: Re: [postgis-users] couldn't get the correct projected values
>
> On May 16, 2008, at 6:55 AM, Obe, Regina wrote:
>
>> What is the SRID of your il_izmir3 geometry to begin with?
>>
>> If you imported it and incorrectly stated it as 32635 rather than
>> 4269 or 4326, then presumably the transform will do nothing since
>> it will see 32635 -> 32635 (you are already - nothing to do here).
>
> Excellent idea! But if this is the case, shouldn't the first thing to
> do be to fix the original table:
>
> 	update il_izmir3 set the_geom = ST_SetSRID(the_geom, 4326);
>
> and then Ahmet's original step 1 should work.
>
> -- Andy
>
>>
>> I am going to guess that the SRID of your il_izmir3 is incorrectly
>> stated and that to fix, scrap the second statement and change your
>> first statement to  (note if your data is NAD83 longlat rather than
>> WGS long lat change the 4326 to 4269)
>>
>> create table izmir_il4 as select
>> gid,il_kod,iladi,transform(ST_SetSRID(the_geom,4326),32635) as
>> the_geom from il_izmir3;
>>
>> or alternatively change your second statement to
>>
>> UPDATE izmir_il4 SET the_geom=Transform(ST_SetSRID(the_geom,4326),
>> 32635);
>>
>> Note its safer to recreate the table since who knows what
>> projection you stated the first as so you are still transforming a
>> guess to a guess.
>>
>> 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 Paragon
>> Corporation
>> Sent: Friday, May 16, 2008 6:18 AM
>> To: 'PostGIS Users Discussion'
>> Subject: RE: [postgis-users] couldn't get the correct projected  
>> values
>>
>> You are confusing setsrid with transform.
>>
>> Remember setsrid - doesn't change the geometry it simple certifies
>> that a
>> geometry is of a particular projection - basically
>>
>> I am because I say I am
>>
>>
>> Transform - moves a geometry from one projection to another
>>
>> I am not , but please make me so.  Of course the please make me so
>> will fail
>> if you don't know what it is  to begin with
>>
>>
>> So all being said, your statement 2 is wrong and should be
>>
>> update izmir_il4 set the_geom=Transform(the_geom,32635);
>>
>> 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
>> orkun
>> Sent: Friday, May 16, 2008 4:00 AM
>> To: postgis-users at postgis.refractions.net
>> Subject: [postgis-users] couldn't get the correct projected values
>>
>> hello
>>
>> whatever I have done, I couldn't get the correct projected values
>> in postgis
>> environment.
>>
>> 1. # lon/lat to utm projection
>>
>> create table izmir_il4 as select
>> gid,il_kod,iladi,transform(the_geom,32635) as the_geom from  
>> il_izmir3;
>>
>> 2.
>> update izmir_il4 set the_geom=setsrid(the_geom,32635);
>>
>> 3.
>>
>> select extent(the_geom) from izmir_il4;
>>
>> extent
>> --------------------------------------------------------------------- 
>> -
>> ----
>> BOX(26.2226982116699 37.8668251037598,28.4587249755859
>> 39.3925666809082)
>>
>> but these are not utm values. They are still in lon/lat values
>>
>> I checked extent values with proj values. I got correct values:
>>
>> echo "26.2226982116699 37.8668251037598" | proj +proj=utm +zone=35
>> +ellps=WGS84 +datum=WGS84
>> 431631.23       4191323.84
>> orkun at orkun-desktop:/usr/local/izmir/veri/izmir3$ echo
>> "28.4587249755859
>> 39.3925666809082" | proj +proj=utm +zone=35 +ellps=WGS84 +datum=WGS84
>> 625615.27       4361356.53
>>
>>
>> how can get values generated from "proj" in postgis environment ?
>> what am I doing wrong ?
>>
>> here is the srid values of 32635 :
>> 32635 | +proj=utm +zone=35 +ellps=WGS84 +datum=WGS84 +units=m  
>> +no_defs
>>
>> regards
>>
>> --
>> Ahmet Temiz
>> Jeo. Müh.
>> Afet Isleri Gen. Md.lügü
>> Deprem Ar. D.
>>
>> Ahmet Temiz
>> Geo. Eng.
>> General Dir. of
>> Disaster Affairs
>>
>>
>>
>> -- 
>> This message has been scanned for viruses and
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>>
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