[mapserver-users] Converting datum using ogr2ogr

[NASUNO Isao]

Hi Jukka,

Thank you for your response.

yes, I tried with the options (s/t_srs), however it makes conversion
for projection but not for datum.

In my case, I used following options but the input and output
are exactly same.

  -s_srs "EPSG:4301"   -t_srs "EPSG:4326"
  (GCS with bessel)    (GCS with WGS84)

I checked GDAL FAQ and found following.

http://trac.osgeo.org/gdal/wiki/FAQCoordinateSystemsAndProjections#WhydoesntGDALautomaticallychoosethedatumtransformation
------------------------------------
Why doesn't GDAL automatically choose the datum transformation?
  There is no such thing as an accurate "default" set of datum transformation
  parameters for a datum. OGR uses (NADCON) by default, which is the most
  accurate available for North America, but in the general case (worldwide)
  this is very hard to determine and there normally is no such thing as a default.
  The transformation that should be used depends on the exact area covered,
  accuracy required etc. In other words, user beware and do your homework.
------------------------------------

Is this the reason ?
I am not sure if ogr2ogr can accept the parameters in manual.
Please help if any idea.

Thanks,

Isao


Rahkonen Jukka wrote:
> Hi,
> 
> I don't think you need .prj file with your shapefiles and you should be able even to overrun it.
> You need to use parameters -s_srs for source projection and -t_srs for target projection.
> 
> -Jukka Rahkonen-
> 
> 
> -----Alkuperäinen viesti-----
> Lähettäjä: mapserver-users-bounces at lists.osgeo.org puolesta: NASUNO Isao
> Lähetetty: to 15.5.2008 4:59
> Vastaanottaja: mapserver-users at lists.osgeo.org
> Aihe: [mapserver-users] Converting datum using ogr2ogr
>  
> Hello,
> 
> I am new in the mailing list.
> 
> I want to use ogr2ogr to convert projection/datum of shape files to
> a same SRS before insert them into postgres for serving by MapServer.
> 
> However ogr2ogr seems convert only projection even the shape file has .prj file.
> I checked out that GDAL has no default parameters to convert datum.
> 
> I need the conversion before inserting to postgres with some reasons,
> I mean, with translation from shape to shape.
> 
> Any suggestion to convert datum using ogr2ogr or other stand-alone program ?
> - The ogr2ogr is included in FWTools 2.1.0.
> - OS is windows xp.
> 
> Thanks,
> 
> Isao NASUNO
>