[postgis-users] Converting UTM to lat/lon using Postgis

[pcreso at pcreso.com]

See:

http://www.spatialreference.org/ref/epsg/3997/postgis/
for the insert statement to create this projection in Postgis.

For other information about this projection see:
http://www.spatialreference.org/ref/epsg/3997/

HTH,

  Brent Wood
--- On Mon, 5/3/10, Mehmet Erkek <merkek at reidin.com> wrote:

From: Mehmet Erkek <merkek at reidin.com>
Subject: Re: [postgis-users] Converting UTM to lat/lon using Postgis
To: "PostGIS Users Discussion" <postgis-users at postgis.refractions.net>
Date: Monday, May 3, 2010, 7:50 PM




 
 






Thank you for the fast answer! 

   

Hmm. It looks I don’t have srid 3997 in the DB. 

   

   

=# select srid, srtext, proj4text from spatial_ref_sys where
srid=3997; 

 srid | srtext | proj4text 

------+--------+----------- 

(0 rows) 

   

select srid, srtext, proj4text from spatial_ref_sys where 
srtext like '%Dubai%'; 

 srid | srtext | proj4text 

------+--------+----------- 

(0 rows) 

   

   

Could this be related to my postgis installation?  

   

I don’t see this srid in spatial_ref_sys.sql which came
with postgis installation either.  

   

Any idea how I can fix this? 

   

   

------------------------------------------------------------------- 

Mehmet ERKEK 

www.REIDIN.com 

   



From:
postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Francis
Markham

Sent: Monday, May 03, 2010 11:09 AM

To: PostGIS Users Discussion

Subject: Re: [postgis-users] Converting UTM to lat/lon using Postgis 



   

Hi Mehmet,



When you imported the shapefile, the SRID you are meant to specify is the SRID
of the data, not the SRID you want.  Since the data is in Dubai Local TM,
the SRID is 3997.  To get the transformation you want, try the following: 

select  
ST_AsText( ST_Transform(centroid(ST_SetSRID(the_geom, 3997)),4326)) from
ult.test2 limit 5; 

Hope that helps,



-Francis 



On 3 May 2010 17:03, Mehmet Erkek <merkek at reidin.com> wrote: 





  

Hi
All, 

  

I
havea a shape file which I imported it to a table called ‘test2’
(using  SRID=4326).  I want to get centroids of geometries in
lat/lon.  

  

Here
is what I run: 

  

select  
ST_AsText( ST_Transform(centroid(the_geom),4326)) from ult.test2 limit 5; 

  

and
what I get: 

  

POINT(496597.996430787
2774798.21242881) 

POINT(496332.629887436
2793339.61534586) 

POINT(496302.627327975
2793317.82477318) 

POINT(496305.255261594
2793353.29646291) 

POINT(496241.538851096
2774826.65593589) 

  

  

So
far all is fine except coordinates which are not  latitude/longitude  

  

My
question is : How can I convert/get these coordinates in lat/lon? 

  

  

This
what I have in my prj file:  

  

PROJCS["Dubai
Local Transverse Mercator
(DLTM)",GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Transverse_Mercator"],PARAMETER["False_Easting",500000.0],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",55.33333333333334],PARAMETER["Scale_Factor",1.0],PARAMETER["Latitude_Of_Origin",0.0],UNIT["Meter",1.0]] 

  

  

And
this is my postgis version: POSTGIS="1.3.6"
GEOS="2.2.3-CAPI-1.1.1" PROJ="Rel. 4.7.1, 23 September 2009"
USE_STATS 

  

I
appreciate any help. Thank you. 

  

  

------------------------------------------------------------------- 

Mehmet ERKEK 

www.REIDIN.com 

  





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